Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt

Pull fscrypt updates from Eric Biggers:
 "This is a large update to fs/crypto/ which includes:

   - Add ioctls that add/remove encryption keys to/from a
     filesystem-level keyring.

     These fix user-reported issues where e.g. an encrypted home
     directory can break NetworkManager, sshd, Docker, etc. because they
     don't get access to the needed keyring. These ioctls also provide a
     way to lock encrypted directories that doesn't use the
     vm.drop_caches sysctl, so is faster, more reliable, and doesn't
     always need root.

   - Add a new encryption policy version ("v2") which switches to a more
     standard, secure, and flexible key derivation function, and starts
     verifying that the correct key was supplied before using it.

     The key derivation improvement is needed for its own sake as well
     as for ongoing feature work for which the current way is too
     inflexible.

  Work is in progress to update both Android and the 'fscrypt' userspace
  tool to use both these features. (Working patches are available and
  just need to be reviewed+merged.) Chrome OS will likely use them too.

  This has also been tested on ext4, f2fs, and ubifs with xfstests --
  both the existing encryption tests, and the new tests for this. This
  has also been in linux-next since Aug 16 with no reported issues. I'm
  also using an fscrypt v2-encrypted home directory on my personal
  desktop"

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt: (27 commits)
  ext4 crypto: fix to check feature status before get policy
  fscrypt: document the new ioctls and policy version
  ubifs: wire up new fscrypt ioctls
  f2fs: wire up new fscrypt ioctls
  ext4: wire up new fscrypt ioctls
  fscrypt: require that key be added when setting a v2 encryption policy
  fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS ioctl
  fscrypt: allow unprivileged users to add/remove keys for v2 policies
  fscrypt: v2 encryption policy support
  fscrypt: add an HKDF-SHA512 implementation
  fscrypt: add FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl
  fscrypt: add FS_IOC_REMOVE_ENCRYPTION_KEY ioctl
  fscrypt: add FS_IOC_ADD_ENCRYPTION_KEY ioctl
  fscrypt: rename keyinfo.c to keysetup.c
  fscrypt: move v1 policy key setup to keysetup_v1.c
  fscrypt: refactor key setup code in preparation for v2 policies
  fscrypt: rename fscrypt_master_key to fscrypt_direct_key
  fscrypt: add ->ci_inode to fscrypt_info
  fscrypt: use FSCRYPT_* definitions, not FS_*
  fscrypt: use FSCRYPT_ prefix for uapi constants
  ...

Documentation/filesystems/fscrypt.rst

@@ -72,6 +72,9 @@ Online attacks
 fscrypt (and storage encryption in general) can only provide limited
 protection, if any at all, against online attacks.  In detail:
 
+Side-channel attacks
+~~~~~~~~~~~~~~~~~~~~
+
 fscrypt is only resistant to side-channel attacks, such as timing or
 electromagnetic attacks, to the extent that the underlying Linux
 Cryptographic API algorithms are.  If a vulnerable algorithm is used,
@@ -80,29 +83,90 @@ attacker to mount a side channel attack against the online system.
 Side channel attacks may also be mounted against applications
 consuming decrypted data.
 
-After an encryption key has been provided, fscrypt is not designed to
-hide the plaintext file contents or filenames from other users on the
-same system, regardless of the visibility of the keyring key.
-Instead, existing access control mechanisms such as file mode bits,
-POSIX ACLs, LSMs, or mount namespaces should be used for this purpose.
-Also note that as long as the encryption keys are *anywhere* in
-memory, an online attacker can necessarily compromise them by mounting
-a physical attack or by exploiting any kernel security vulnerability
-which provides an arbitrary memory read primitive.
-
-While it is ostensibly possible to "evict" keys from the system,
-recently accessed encrypted files will remain accessible at least
-until the filesystem is unmounted or the VFS caches are dropped, e.g.
-using ``echo 2 > /proc/sys/vm/drop_caches``.  Even after that, if the
-RAM is compromised before being powered off, it will likely still be
-possible to recover portions of the plaintext file contents, if not
-some of the encryption keys as well.  (Since Linux v4.12, all
-in-kernel keys related to fscrypt are sanitized before being freed.
-However, userspace would need to do its part as well.)
-
-Currently, fscrypt does not prevent a user from maliciously providing
-an incorrect key for another user's existing encrypted files.  A
-protection against this is planned.
+Unauthorized file access
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+After an encryption key has been added, fscrypt does not hide the
+plaintext file contents or filenames from other users on the same
+system.  Instead, existing access control mechanisms such as file mode
+bits, POSIX ACLs, LSMs, or namespaces should be used for this purpose.
+
+(For the reasoning behind this, understand that while the key is
+added, the confidentiality of the data, from the perspective of the
+system itself, is *not* protected by the mathematical properties of
+encryption but rather only by the correctness of the kernel.
+Therefore, any encryption-specific access control checks would merely
+be enforced by kernel *code* and therefore would be largely redundant
+with the wide variety of access control mechanisms already available.)
+
+Kernel memory compromise
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+An attacker who compromises the system enough to read from arbitrary
+memory, e.g. by mounting a physical attack or by exploiting a kernel
+security vulnerability, can compromise all encryption keys that are
+currently in use.
+
+However, fscrypt allows encryption keys to be removed from the kernel,
+which may protect them from later compromise.
+
+In more detail, the FS_IOC_REMOVE_ENCRYPTION_KEY ioctl (or the
+FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS ioctl) can wipe a master
+encryption key from kernel memory.  If it does so, it will also try to
+evict all cached inodes which had been "unlocked" using the key,
+thereby wiping their per-file keys and making them once again appear
+"locked", i.e. in ciphertext or encrypted form.
+
+However, these ioctls have some limitations:
+
+- Per-file keys for in-use files will *not* be removed or wiped.
+  Therefore, for maximum effect, userspace should close the relevant
+  encrypted files and directories before removing a master key, as
+  well as kill any processes whose working directory is in an affected
+  encrypted directory.
+
+- The kernel cannot magically wipe copies of the master key(s) that
+  userspace might have as well.  Therefore, userspace must wipe all
+  copies of the master key(s) it makes as well; normally this should
+  be done immediately after FS_IOC_ADD_ENCRYPTION_KEY, without waiting
+  for FS_IOC_REMOVE_ENCRYPTION_KEY.  Naturally, the same also applies
+  to all higher levels in the key hierarchy.  Userspace should also
+  follow other security precautions such as mlock()ing memory
+  containing keys to prevent it from being swapped out.
+
+- In general, decrypted contents and filenames in the kernel VFS
+  caches are freed but not wiped.  Therefore, portions thereof may be
+  recoverable from freed memory, even after the corresponding key(s)
+  were wiped.  To partially solve this, you can set
+  CONFIG_PAGE_POISONING=y in your kernel config and add page_poison=1
+  to your kernel command line.  However, this has a performance cost.
+
+- Secret keys might still exist in CPU registers, in crypto
+  accelerator hardware (if used by the crypto API to implement any of
+  the algorithms), or in other places not explicitly considered here.
+
+Limitations of v1 policies
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+v1 encryption policies have some weaknesses with respect to online
+attacks:
+
+- There is no verification that the provided master key is correct.
+  Therefore, a malicious user can temporarily associate the wrong key
+  with another user's encrypted files to which they have read-only
+  access.  Because of filesystem caching, the wrong key will then be
+  used by the other user's accesses to those files, even if the other
+  user has the correct key in their own keyring.  This violates the
+  meaning of "read-only access".
+
+- A compromise of a per-file key also compromises the master key from
+  which it was derived.
+
+- Non-root users cannot securely remove encryption keys.
+
+All the above problems are fixed with v2 encryption policies.  For
+this reason among others, it is recommended to use v2 encryption
+policies on all new encrypted directories.
 
 Key hierarchy
 =============
@@ -123,11 +187,52 @@ appropriate master key.  There can be any number of master keys, each
 of which protects any number of directory trees on any number of
 filesystems.
 
-Userspace should generate master keys either using a cryptographically
-secure random number generator, or by using a KDF (Key Derivation
-Function).  Note that whenever a KDF is used to "stretch" a
-lower-entropy secret such as a passphrase, it is critical that a KDF
-designed for this purpose be used, such as scrypt, PBKDF2, or Argon2.
+Master keys must be real cryptographic keys, i.e. indistinguishable
+from random bytestrings of the same length.  This implies that users
+**must not** directly use a password as a master key, zero-pad a
+shorter key, or repeat a shorter key.  Security cannot be guaranteed
+if userspace makes any such error, as the cryptographic proofs and
+analysis would no longer apply.
+
+Instead, users should generate master keys either using a
+cryptographically secure random number generator, or by using a KDF
+(Key Derivation Function).  The kernel does not do any key stretching;
+therefore, if userspace derives the key from a low-entropy secret such
+as a passphrase, it is critical that a KDF designed for this purpose
+be used, such as scrypt, PBKDF2, or Argon2.
+
+Key derivation function
+-----------------------
+
+With one exception, fscrypt never uses the master key(s) for
+encryption directly.  Instead, they are only used as input to a KDF
+(Key Derivation Function) to derive the actual keys.
+
+The KDF used for a particular master key differs depending on whether
+the key is used for v1 encryption policies or for v2 encryption
+policies.  Users **must not** use the same key for both v1 and v2
+encryption policies.  (No real-world attack is currently known on this
+specific case of key reuse, but its security cannot be guaranteed
+since the cryptographic proofs and analysis would no longer apply.)
+
+For v1 encryption policies, the KDF only supports deriving per-file
+encryption keys.  It works by encrypting the master key with
+AES-128-ECB, using the file's 16-byte nonce as the AES key.  The
+resulting ciphertext is used as the derived key.  If the ciphertext is
+longer than needed, then it is truncated to the needed length.
+
+For v2 encryption policies, the KDF is HKDF-SHA512.  The master key is
+passed as the "input keying material", no salt is used, and a distinct
+"application-specific information string" is used for each distinct
+key to be derived.  For example, when a per-file encryption key is
+derived, the application-specific information string is the file's
+nonce prefixed with "fscrypt\\0" and a context byte.  Different
+context bytes are used for other types of derived keys.
+
+HKDF-SHA512 is preferred to the original AES-128-ECB based KDF because
+HKDF is more flexible, is nonreversible, and evenly distributes
+entropy from the master key.  HKDF is also standardized and widely
+used by other software, whereas the AES-128-ECB based KDF is ad-hoc.
 
 Per-file keys
 -------------
@@ -138,29 +243,9 @@ files doesn't map to the same ciphertext, or vice versa.  In most
 cases, fscrypt does this by deriving per-file keys.  When a new
 encrypted inode (regular file, directory, or symlink) is created,
 fscrypt randomly generates a 16-byte nonce and stores it in the
-inode's encryption xattr.  Then, it uses a KDF (Key Derivation
-Function) to derive the file's key from the master key and nonce.
-
-The Adiantum encryption mode (see `Encryption modes and usage`_) is
-special, since it accepts longer IVs and is suitable for both contents
-and filenames encryption.  For it, a "direct key" option is offered
-where the file's nonce is included in the IVs and the master key is
-used for encryption directly.  This improves performance; however,
-users must not use the same master key for any other encryption mode.
-
-Below, the KDF and design considerations are described in more detail.
-
-The current KDF works by encrypting the master key with AES-128-ECB,
-using the file's nonce as the AES key.  The output is used as the
-derived key.  If the output is longer than needed, then it is
-truncated to the needed length.
-
-Note: this KDF meets the primary security requirement, which is to
-produce unique derived keys that preserve the entropy of the master
-key, assuming that the master key is already a good pseudorandom key.
-However, it is nonstandard and has some problems such as being
-reversible, so it is generally considered to be a mistake!  It may be
-replaced with HKDF or another more standard KDF in the future.
+inode's encryption xattr.  Then, it uses a KDF (as described in `Key
+derivation function`_) to derive the file's key from the master key
+and nonce.
 
 Key derivation was chosen over key wrapping because wrapped keys would
 require larger xattrs which would be less likely to fit in-line in the
@@ -176,6 +261,37 @@ rejected as it would have prevented ext4 filesystems from being
 resized, and by itself still wouldn't have been sufficient to prevent
 the same key from being directly reused for both XTS and CTS-CBC.
 
+DIRECT_KEY and per-mode keys
+----------------------------
+
+The Adiantum encryption mode (see `Encryption modes and usage`_) is
+suitable for both contents and filenames encryption, and it accepts
+long IVs --- long enough to hold both an 8-byte logical block number
+and a 16-byte per-file nonce.  Also, the overhead of each Adiantum key
+is greater than that of an AES-256-XTS key.
+
+Therefore, to improve performance and save memory, for Adiantum a
+"direct key" configuration is supported.  When the user has enabled
+this by setting FSCRYPT_POLICY_FLAG_DIRECT_KEY in the fscrypt policy,
+per-file keys are not used.  Instead, whenever any data (contents or
+filenames) is encrypted, the file's 16-byte nonce is included in the
+IV.  Moreover:
+
+- For v1 encryption policies, the encryption is done directly with the
+  master key.  Because of this, users **must not** use the same master
+  key for any other purpose, even for other v1 policies.
+
+- For v2 encryption policies, the encryption is done with a per-mode
+  key derived using the KDF.  Users may use the same master key for
+  other v2 encryption policies.
+
+Key identifiers
+---------------
+
+For master keys used for v2 encryption policies, a unique 16-byte "key
+identifier" is also derived using the KDF.  This value is stored in
+the clear, since it is needed to reliably identify the key itself.
+
 Encryption modes and usage
 ==========================
 
@@ -225,9 +341,10 @@ a little endian number, except that:
   is encrypted with AES-256 where the AES-256 key is the SHA-256 hash
   of the file's data encryption key.
 
-- In the "direct key" configuration (FS_POLICY_FLAG_DIRECT_KEY set in
-  the fscrypt_policy), the file's nonce is also appended to the IV.
-  Currently this is only allowed with the Adiantum encryption mode.
+- In the "direct key" configuration (FSCRYPT_POLICY_FLAG_DIRECT_KEY
+  set in the fscrypt_policy), the file's nonce is also appended to the
+  IV.  Currently this is only allowed with the Adiantum encryption
+  mode.
 
 Filenames encryption
 --------------------
@@ -269,49 +386,77 @@ User API
 Setting an encryption policy
 ----------------------------
 
+FS_IOC_SET_ENCRYPTION_POLICY
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
 The FS_IOC_SET_ENCRYPTION_POLICY ioctl sets an encryption policy on an
 empty directory or verifies that a directory or regular file already
 has the specified encryption policy.  It takes in a pointer to a
-:c:type:`struct fscrypt_policy`, defined as follows::
+:c:type:`struct fscrypt_policy_v1` or a :c:type:`struct
+fscrypt_policy_v2`, defined as follows::
 
-    #define FS_KEY_DESCRIPTOR_SIZE  8
+    #define FSCRYPT_POLICY_V1               0
+    #define FSCRYPT_KEY_DESCRIPTOR_SIZE     8
+    struct fscrypt_policy_v1 {
+            __u8 version;
+            __u8 contents_encryption_mode;
+            __u8 filenames_encryption_mode;
+            __u8 flags;
+            __u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+    };
+    #define fscrypt_policy  fscrypt_policy_v1
 
-    struct fscrypt_policy {
+    #define FSCRYPT_POLICY_V2               2
+    #define FSCRYPT_KEY_IDENTIFIER_SIZE     16
+    struct fscrypt_policy_v2 {
             __u8 version;
             __u8 contents_encryption_mode;
             __u8 filenames_encryption_mode;
             __u8 flags;
-            __u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+            __u8 __reserved[4];
+            __u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
     };
 
 This structure must be initialized as follows:
 
-- ``version`` must be 0.
+- ``version`` must be FSCRYPT_POLICY_V1 (0) if the struct is
+  :c:type:`fscrypt_policy_v1` or FSCRYPT_POLICY_V2 (2) if the struct
+  is :c:type:`fscrypt_policy_v2`.  (Note: we refer to the original
+  policy version as "v1", though its version code is really 0.)  For
+  new encrypted directories, use v2 policies.
 
 - ``contents_encryption_mode`` and ``filenames_encryption_mode`` must
-  be set to constants from ``<linux/fs.h>`` which identify the
-  encryption modes to use.  If unsure, use
-  FS_ENCRYPTION_MODE_AES_256_XTS (1) for ``contents_encryption_mode``
-  and FS_ENCRYPTION_MODE_AES_256_CTS (4) for
-  ``filenames_encryption_mode``.
+  be set to constants from ``<linux/fscrypt.h>`` which identify the
+  encryption modes to use.  If unsure, use FSCRYPT_MODE_AES_256_XTS
+  (1) for ``contents_encryption_mode`` and FSCRYPT_MODE_AES_256_CTS
+  (4) for ``filenames_encryption_mode``.
 
-- ``flags`` must contain a value from ``<linux/fs.h>`` which
+- ``flags`` must contain a value from ``<linux/fscrypt.h>`` which
   identifies the amount of NUL-padding to use when encrypting
-  filenames.  If unsure, use FS_POLICY_FLAGS_PAD_32 (0x3).
-  In addition, if the chosen encryption modes are both
-  FS_ENCRYPTION_MODE_ADIANTUM, this can contain
-  FS_POLICY_FLAG_DIRECT_KEY to specify that the master key should be
-  used directly, without key derivation.
-
-- ``master_key_descriptor`` specifies how to find the master key in
-  the keyring; see `Adding keys`_.  It is up to userspace to choose a
-  unique ``master_key_descriptor`` for each master key.  The e4crypt
-  and fscrypt tools use the first 8 bytes of
+  filenames.  If unsure, use FSCRYPT_POLICY_FLAGS_PAD_32 (0x3).
+  Additionally, if the encryption modes are both
+  FSCRYPT_MODE_ADIANTUM, this can contain
+  FSCRYPT_POLICY_FLAG_DIRECT_KEY; see `DIRECT_KEY and per-mode keys`_.
+
+- For v2 encryption policies, ``__reserved`` must be zeroed.
+
+- For v1 encryption policies, ``master_key_descriptor`` specifies how
+  to find the master key in a keyring; see `Adding keys`_.  It is up
+  to userspace to choose a unique ``master_key_descriptor`` for each
+  master key.  The e4crypt and fscrypt tools use the first 8 bytes of
   ``SHA-512(SHA-512(master_key))``, but this particular scheme is not
   required.  Also, the master key need not be in the keyring yet when
   FS_IOC_SET_ENCRYPTION_POLICY is executed.  However, it must be added
   before any files can be created in the encrypted directory.
 
+  For v2 encryption policies, ``master_key_descriptor`` has been
+  replaced with ``master_key_identifier``, which is longer and cannot
+  be arbitrarily chosen.  Instead, the key must first be added using
+  `FS_IOC_ADD_ENCRYPTION_KEY`_.  Then, the ``key_spec.u.identifier``
+  the kernel returned in the :c:type:`struct fscrypt_add_key_arg` must
+  be used as the ``master_key_identifier`` in the :c:type:`struct
+  fscrypt_policy_v2`.
+
 If the file is not yet encrypted, then FS_IOC_SET_ENCRYPTION_POLICY
 verifies that the file is an empty directory.  If so, the specified
 encryption policy is assigned to the directory, turning it into an
@@ -327,6 +472,15 @@ policy exactly matches the actual one.  If they match, then the ioctl
 returns 0.  Otherwise, it fails with EEXIST.  This works on both
 regular files and directories, including nonempty directories.
 
+When a v2 encryption policy is assigned to a directory, it is also
+required that either the specified key has been added by the current
+user or that the caller has CAP_FOWNER in the initial user namespace.
+(This is needed to prevent a user from encrypting their data with
+another user's key.)  The key must remain added while
+FS_IOC_SET_ENCRYPTION_POLICY is executing.  However, if the new
+encrypted directory does not need to be accessed immediately, then the
+key can be removed right away afterwards.
+
 Note that the ext4 filesystem does not allow the root directory to be
 encrypted, even if it is empty.  Users who want to encrypt an entire
 filesystem with one key should consider using dm-crypt instead.
@@ -339,7 +493,11 @@ FS_IOC_SET_ENCRYPTION_POLICY can fail with the following errors:
 - ``EEXIST``: the file is already encrypted with an encryption policy
   different from the one specified
 - ``EINVAL``: an invalid encryption policy was specified (invalid
-  version, mode(s), or flags)
+  version, mode(s), or flags; or reserved bits were set)
+- ``ENOKEY``: a v2 encryption policy was specified, but the key with
+  the specified ``master_key_identifier`` has not been added, nor does
+  the process have the CAP_FOWNER capability in the initial user
+  namespace
 - ``ENOTDIR``: the file is unencrypted and is a regular file, not a
   directory
 - ``ENOTEMPTY``: the file is unencrypted and is a nonempty directory
@@ -358,25 +516,79 @@ FS_IOC_SET_ENCRYPTION_POLICY can fail with the following errors:
 Getting an encryption policy
 ----------------------------
 
-The FS_IOC_GET_ENCRYPTION_POLICY ioctl retrieves the :c:type:`struct
-fscrypt_policy`, if any, for a directory or regular file.  See above
-for the struct definition.  No additional permissions are required
-beyond the ability to open the file.
+Two ioctls are available to get a file's encryption policy:
+
+- `FS_IOC_GET_ENCRYPTION_POLICY_EX`_
+- `FS_IOC_GET_ENCRYPTION_POLICY`_
+
+The extended (_EX) version of the ioctl is more general and is
+recommended to use when possible.  However, on older kernels only the
+original ioctl is available.  Applications should try the extended
+version, and if it fails with ENOTTY fall back to the original
+version.
+
+FS_IOC_GET_ENCRYPTION_POLICY_EX
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The FS_IOC_GET_ENCRYPTION_POLICY_EX ioctl retrieves the encryption
+policy, if any, for a directory or regular file.  No additional
+permissions are required beyond the ability to open the file.  It
+takes in a pointer to a :c:type:`struct fscrypt_get_policy_ex_arg`,
+defined as follows::
+
+    struct fscrypt_get_policy_ex_arg {
+            __u64 policy_size; /* input/output */
+            union {
+                    __u8 version;
+                    struct fscrypt_policy_v1 v1;
+                    struct fscrypt_policy_v2 v2;
+            } policy; /* output */
+    };
+
+The caller must initialize ``policy_size`` to the size available for
+the policy struct, i.e. ``sizeof(arg.policy)``.
+
+On success, the policy struct is returned in ``policy``, and its
+actual size is returned in ``policy_size``.  ``policy.version`` should
+be checked to determine the version of policy returned.  Note that the
+version code for the "v1" policy is actually 0 (FSCRYPT_POLICY_V1).
 
-FS_IOC_GET_ENCRYPTION_POLICY can fail with the following errors:
+FS_IOC_GET_ENCRYPTION_POLICY_EX can fail with the following errors:
 
 - ``EINVAL``: the file is encrypted, but it uses an unrecognized
-  encryption context format
+  encryption policy version
 - ``ENODATA``: the file is not encrypted
-- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``ENOTTY``: this type of filesystem does not implement encryption,
+  or this kernel is too old to support FS_IOC_GET_ENCRYPTION_POLICY_EX
+  (try FS_IOC_GET_ENCRYPTION_POLICY instead)
 - ``EOPNOTSUPP``: the kernel was not configured with encryption
-  support for this filesystem
+  support for this filesystem, or the filesystem superblock has not
+  had encryption enabled on it
+- ``EOVERFLOW``: the file is encrypted and uses a recognized
+  encryption policy version, but the policy struct does not fit into
+  the provided buffer
 
 Note: if you only need to know whether a file is encrypted or not, on
 most filesystems it is also possible to use the FS_IOC_GETFLAGS ioctl
 and check for FS_ENCRYPT_FL, or to use the statx() system call and
 check for STATX_ATTR_ENCRYPTED in stx_attributes.
 
+FS_IOC_GET_ENCRYPTION_POLICY
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The FS_IOC_GET_ENCRYPTION_POLICY ioctl can also retrieve the
+encryption policy, if any, for a directory or regular file.  However,
+unlike `FS_IOC_GET_ENCRYPTION_POLICY_EX`_,
+FS_IOC_GET_ENCRYPTION_POLICY only supports the original policy
+version.  It takes in a pointer directly to a :c:type:`struct
+fscrypt_policy_v1` rather than a :c:type:`struct
+fscrypt_get_policy_ex_arg`.
+
+The error codes for FS_IOC_GET_ENCRYPTION_POLICY are the same as those
+for FS_IOC_GET_ENCRYPTION_POLICY_EX, except that
+FS_IOC_GET_ENCRYPTION_POLICY also returns ``EINVAL`` if the file is
+encrypted using a newer encryption policy version.
+
 Getting the per-filesystem salt
 -------------------------------
 
@@ -392,8 +604,115 @@ generate and manage any needed salt(s) in userspace.
 Adding keys
 -----------
 
-To provide a master key, userspace must add it to an appropriate
-keyring using the add_key() system call (see:
+FS_IOC_ADD_ENCRYPTION_KEY
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The FS_IOC_ADD_ENCRYPTION_KEY ioctl adds a master encryption key to
+the filesystem, making all files on the filesystem which were
+encrypted using that key appear "unlocked", i.e. in plaintext form.
+It can be executed on any file or directory on the target filesystem,
+but using the filesystem's root directory is recommended.  It takes in
+a pointer to a :c:type:`struct fscrypt_add_key_arg`, defined as
+follows::
+
+    struct fscrypt_add_key_arg {
+            struct fscrypt_key_specifier key_spec;
+            __u32 raw_size;
+            __u32 __reserved[9];
+            __u8 raw[];
+    };
+
+    #define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR        1
+    #define FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER        2
+
+    struct fscrypt_key_specifier {
+            __u32 type;     /* one of FSCRYPT_KEY_SPEC_TYPE_* */
+            __u32 __reserved;
+            union {
+                    __u8 __reserved[32]; /* reserve some extra space */
+                    __u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+                    __u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+            } u;
+    };
+
+:c:type:`struct fscrypt_add_key_arg` must be zeroed, then initialized
+as follows:
+
+- If the key is being added for use by v1 encryption policies, then
+  ``key_spec.type`` must contain FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR, and
+  ``key_spec.u.descriptor`` must contain the descriptor of the key
+  being added, corresponding to the value in the
+  ``master_key_descriptor`` field of :c:type:`struct
+  fscrypt_policy_v1`.  To add this type of key, the calling process
+  must have the CAP_SYS_ADMIN capability in the initial user
+  namespace.
+
+  Alternatively, if the key is being added for use by v2 encryption
+  policies, then ``key_spec.type`` must contain
+  FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER, and ``key_spec.u.identifier`` is
+  an *output* field which the kernel fills in with a cryptographic
+  hash of the key.  To add this type of key, the calling process does
+  not need any privileges.  However, the number of keys that can be
+  added is limited by the user's quota for the keyrings service (see
+  ``Documentation/security/keys/core.rst``).
+
+- ``raw_size`` must be the size of the ``raw`` key provided, in bytes.
+
+- ``raw`` is a variable-length field which must contain the actual
+  key, ``raw_size`` bytes long.
+
+For v2 policy keys, the kernel keeps track of which user (identified
+by effective user ID) added the key, and only allows the key to be
+removed by that user --- or by "root", if they use
+`FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS`_.
+
+However, if another user has added the key, it may be desirable to
+prevent that other user from unexpectedly removing it.  Therefore,
+FS_IOC_ADD_ENCRYPTION_KEY may also be used to add a v2 policy key
+*again*, even if it's already added by other user(s).  In this case,
+FS_IOC_ADD_ENCRYPTION_KEY will just install a claim to the key for the
+current user, rather than actually add the key again (but the raw key
+must still be provided, as a proof of knowledge).
+
+FS_IOC_ADD_ENCRYPTION_KEY returns 0 if either the key or a claim to
+the key was either added or already exists.
+
+FS_IOC_ADD_ENCRYPTION_KEY can fail with the following errors:
+
+- ``EACCES``: FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR was specified, but the
+  caller does not have the CAP_SYS_ADMIN capability in the initial
+  user namespace
+- ``EDQUOT``: the key quota for this user would be exceeded by adding
+  the key
+- ``EINVAL``: invalid key size or key specifier type, or reserved bits
+  were set
+- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``EOPNOTSUPP``: the kernel was not configured with encryption
+  support for this filesystem, or the filesystem superblock has not
+  had encryption enabled on it
+
+Legacy method
+~~~~~~~~~~~~~
+
+For v1 encryption policies, a master encryption key can also be
+provided by adding it to a process-subscribed keyring, e.g. to a
+session keyring, or to a user keyring if the user keyring is linked
+into the session keyring.
+
+This method is deprecated (and not supported for v2 encryption
+policies) for several reasons.  First, it cannot be used in
+combination with FS_IOC_REMOVE_ENCRYPTION_KEY (see `Removing keys`_),
+so for removing a key a workaround such as keyctl_unlink() in
+combination with ``sync; echo 2 > /proc/sys/vm/drop_caches`` would
+have to be used.  Second, it doesn't match the fact that the
+locked/unlocked status of encrypted files (i.e. whether they appear to
+be in plaintext form or in ciphertext form) is global.  This mismatch
+has caused much confusion as well as real problems when processes
+running under different UIDs, such as a ``sudo`` command, need to
+access encrypted files.
+
+Nevertheless, to add a key to one of the process-subscribed keyrings,
+the add_key() system call can be used (see:
 ``Documentation/security/keys/core.rst``).  The key type must be
 "logon"; keys of this type are kept in kernel memory and cannot be
 read back by userspace.  The key description must be "fscrypt:"
@@ -401,12 +720,12 @@ followed by the 16-character lower case hex representation of the
 ``master_key_descriptor`` that was set in the encryption policy.  The
 key payload must conform to the following structure::
 
-    #define FS_MAX_KEY_SIZE 64
+    #define FSCRYPT_MAX_KEY_SIZE            64
 
     struct fscrypt_key {
-            u32 mode;
-            u8 raw[FS_MAX_KEY_SIZE];
-            u32 size;
+            __u32 mode;
+            __u8 raw[FSCRYPT_MAX_KEY_SIZE];
+            __u32 size;
     };
 
 ``mode`` is ignored; just set it to 0.  The actual key is provided in
@@ -418,26 +737,194 @@ with a filesystem-specific prefix such as "ext4:".  However, the
 filesystem-specific prefixes are deprecated and should not be used in
 new programs.
 
-There are several different types of keyrings in which encryption keys
-may be placed, such as a session keyring, a user session keyring, or a
-user keyring.  Each key must be placed in a keyring that is "attached"
-to all processes that might need to access files encrypted with it, in
-the sense that request_key() will find the key.  Generally, if only
-processes belonging to a specific user need to access a given
-encrypted directory and no session keyring has been installed, then
-that directory's key should be placed in that user's user session
-keyring or user keyring.  Otherwise, a session keyring should be
-installed if needed, and the key should be linked into that session
-keyring, or in a keyring linked into that session keyring.
-
-Note: introducing the complex visibility semantics of keyrings here
-was arguably a mistake --- especially given that by design, after any
-process successfully opens an encrypted file (thereby setting up the
-per-file key), possessing the keyring key is not actually required for
-any process to read/write the file until its in-memory inode is
-evicted.  In the future there probably should be a way to provide keys
-directly to the filesystem instead, which would make the intended
-semantics clearer.
+Removing keys
+-------------
+
+Two ioctls are available for removing a key that was added by
+`FS_IOC_ADD_ENCRYPTION_KEY`_:
+
+- `FS_IOC_REMOVE_ENCRYPTION_KEY`_
+- `FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS`_
+
+These two ioctls differ only in cases where v2 policy keys are added
+or removed by non-root users.
+
+These ioctls don't work on keys that were added via the legacy
+process-subscribed keyrings mechanism.
+
+Before using these ioctls, read the `Kernel memory compromise`_
+section for a discussion of the security goals and limitations of
+these ioctls.
+
+FS_IOC_REMOVE_ENCRYPTION_KEY
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The FS_IOC_REMOVE_ENCRYPTION_KEY ioctl removes a claim to a master
+encryption key from the filesystem, and possibly removes the key
+itself.  It can be executed on any file or directory on the target
+filesystem, but using the filesystem's root directory is recommended.
+It takes in a pointer to a :c:type:`struct fscrypt_remove_key_arg`,
+defined as follows::
+
+    struct fscrypt_remove_key_arg {
+            struct fscrypt_key_specifier key_spec;
+    #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY      0x00000001
+    #define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS     0x00000002
+            __u32 removal_status_flags;     /* output */
+            __u32 __reserved[5];
+    };
+
+This structure must be zeroed, then initialized as follows:
+
+- The key to remove is specified by ``key_spec``:
+
+    - To remove a key used by v1 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill
+      in ``key_spec.u.descriptor``.  To remove this type of key, the
+      calling process must have the CAP_SYS_ADMIN capability in the
+      initial user namespace.
+
+    - To remove a key used by v2 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill
+      in ``key_spec.u.identifier``.
+
+For v2 policy keys, this ioctl is usable by non-root users.  However,
+to make this possible, it actually just removes the current user's
+claim to the key, undoing a single call to FS_IOC_ADD_ENCRYPTION_KEY.
+Only after all claims are removed is the key really removed.
+
+For example, if FS_IOC_ADD_ENCRYPTION_KEY was called with uid 1000,
+then the key will be "claimed" by uid 1000, and
+FS_IOC_REMOVE_ENCRYPTION_KEY will only succeed as uid 1000.  Or, if
+both uids 1000 and 2000 added the key, then for each uid
+FS_IOC_REMOVE_ENCRYPTION_KEY will only remove their own claim.  Only
+once *both* are removed is the key really removed.  (Think of it like
+unlinking a file that may have hard links.)
+
+If FS_IOC_REMOVE_ENCRYPTION_KEY really removes the key, it will also
+try to "lock" all files that had been unlocked with the key.  It won't
+lock files that are still in-use, so this ioctl is expected to be used
+in cooperation with userspace ensuring that none of the files are
+still open.  However, if necessary, this ioctl can be executed again
+later to retry locking any remaining files.
+
+FS_IOC_REMOVE_ENCRYPTION_KEY returns 0 if either the key was removed
+(but may still have files remaining to be locked), the user's claim to
+the key was removed, or the key was already removed but had files
+remaining to be the locked so the ioctl retried locking them.  In any
+of these cases, ``removal_status_flags`` is filled in with the
+following informational status flags:
+
+- ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY``: set if some file(s)
+  are still in-use.  Not guaranteed to be set in the case where only
+  the user's claim to the key was removed.
+- ``FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS``: set if only the
+  user's claim to the key was removed, not the key itself
+
+FS_IOC_REMOVE_ENCRYPTION_KEY can fail with the following errors:
+
+- ``EACCES``: The FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR key specifier type
+  was specified, but the caller does not have the CAP_SYS_ADMIN
+  capability in the initial user namespace
+- ``EINVAL``: invalid key specifier type, or reserved bits were set
+- ``ENOKEY``: the key object was not found at all, i.e. it was never
+  added in the first place or was already fully removed including all
+  files locked; or, the user does not have a claim to the key (but
+  someone else does).
+- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``EOPNOTSUPP``: the kernel was not configured with encryption
+  support for this filesystem, or the filesystem superblock has not
+  had encryption enabled on it
+
+FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS is exactly the same as
+`FS_IOC_REMOVE_ENCRYPTION_KEY`_, except that for v2 policy keys, the
+ALL_USERS version of the ioctl will remove all users' claims to the
+key, not just the current user's.  I.e., the key itself will always be
+removed, no matter how many users have added it.  This difference is
+only meaningful if non-root users are adding and removing keys.
+
+Because of this, FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS also requires
+"root", namely the CAP_SYS_ADMIN capability in the initial user
+namespace.  Otherwise it will fail with EACCES.
+
+Getting key status
+------------------
+
+FS_IOC_GET_ENCRYPTION_KEY_STATUS
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The FS_IOC_GET_ENCRYPTION_KEY_STATUS ioctl retrieves the status of a
+master encryption key.  It can be executed on any file or directory on
+the target filesystem, but using the filesystem's root directory is
+recommended.  It takes in a pointer to a :c:type:`struct
+fscrypt_get_key_status_arg`, defined as follows::
+
+    struct fscrypt_get_key_status_arg {
+            /* input */
+            struct fscrypt_key_specifier key_spec;
+            __u32 __reserved[6];
+
+            /* output */
+    #define FSCRYPT_KEY_STATUS_ABSENT               1
+    #define FSCRYPT_KEY_STATUS_PRESENT              2
+    #define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED 3
+            __u32 status;
+    #define FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF   0x00000001
+            __u32 status_flags;
+            __u32 user_count;
+            __u32 __out_reserved[13];
+    };
+
+The caller must zero all input fields, then fill in ``key_spec``:
+
+    - To get the status of a key for v1 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR and fill
+      in ``key_spec.u.descriptor``.
+
+    - To get the status of a key for v2 encryption policies, set
+      ``key_spec.type`` to FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER and fill
+      in ``key_spec.u.identifier``.
+
+On success, 0 is returned and the kernel fills in the output fields:
+
+- ``status`` indicates whether the key is absent, present, or
+  incompletely removed.  Incompletely removed means that the master
+  secret has been removed, but some files are still in use; i.e.,
+  `FS_IOC_REMOVE_ENCRYPTION_KEY`_ returned 0 but set the informational
+  status flag FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY.
+
+- ``status_flags`` can contain the following flags:
+
+    - ``FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF`` indicates that the key
+      has added by the current user.  This is only set for keys
+      identified by ``identifier`` rather than by ``descriptor``.
+
+- ``user_count`` specifies the number of users who have added the key.
+  This is only set for keys identified by ``identifier`` rather than
+  by ``descriptor``.
+
+FS_IOC_GET_ENCRYPTION_KEY_STATUS can fail with the following errors:
+
+- ``EINVAL``: invalid key specifier type, or reserved bits were set
+- ``ENOTTY``: this type of filesystem does not implement encryption
+- ``EOPNOTSUPP``: the kernel was not configured with encryption
+  support for this filesystem, or the filesystem superblock has not
+  had encryption enabled on it
+
+Among other use cases, FS_IOC_GET_ENCRYPTION_KEY_STATUS can be useful
+for determining whether the key for a given encrypted directory needs
+to be added before prompting the user for the passphrase needed to
+derive the key.
+
+FS_IOC_GET_ENCRYPTION_KEY_STATUS can only get the status of keys in
+the filesystem-level keyring, i.e. the keyring managed by
+`FS_IOC_ADD_ENCRYPTION_KEY`_ and `FS_IOC_REMOVE_ENCRYPTION_KEY`_.  It
+cannot get the status of a key that has only been added for use by v1
+encryption policies using the legacy mechanism involving
+process-subscribed keyrings.
 
 Access semantics
 ================
@@ -500,7 +987,7 @@ Without the key
 
 Some filesystem operations may be performed on encrypted regular
 files, directories, and symlinks even before their encryption key has
-been provided:
+been added, or after their encryption key has been removed:
 
 - File metadata may be read, e.g. using stat().
 
@@ -565,33 +1052,44 @@ Encryption context
 ------------------
 
 An encryption policy is represented on-disk by a :c:type:`struct
-fscrypt_context`.  It is up to individual filesystems to decide where
-to store it, but normally it would be stored in a hidden extended
-attribute.  It should *not* be exposed by the xattr-related system
-calls such as getxattr() and setxattr() because of the special
-semantics of the encryption xattr.  (In particular, there would be
-much confusion if an encryption policy were to be added to or removed
-from anything other than an empty directory.)  The struct is defined
-as follows::
-
-    #define FS_KEY_DESCRIPTOR_SIZE  8
+fscrypt_context_v1` or a :c:type:`struct fscrypt_context_v2`.  It is
+up to individual filesystems to decide where to store it, but normally
+it would be stored in a hidden extended attribute.  It should *not* be
+exposed by the xattr-related system calls such as getxattr() and
+setxattr() because of the special semantics of the encryption xattr.
+(In particular, there would be much confusion if an encryption policy
+were to be added to or removed from anything other than an empty
+directory.)  These structs are defined as follows::
+
     #define FS_KEY_DERIVATION_NONCE_SIZE 16
 
-    struct fscrypt_context {
-            u8 format;
+    #define FSCRYPT_KEY_DESCRIPTOR_SIZE  8
+    struct fscrypt_context_v1 {
+            u8 version;
+            u8 contents_encryption_mode;
+            u8 filenames_encryption_mode;
+            u8 flags;
+            u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+            u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
+    };
+
+    #define FSCRYPT_KEY_IDENTIFIER_SIZE  16
+    struct fscrypt_context_v2 {
+            u8 version;
             u8 contents_encryption_mode;
             u8 filenames_encryption_mode;
             u8 flags;
-            u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+            u8 __reserved[4];
+            u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
             u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
     };
 
-Note that :c:type:`struct fscrypt_context` contains the same
-information as :c:type:`struct fscrypt_policy` (see `Setting an
-encryption policy`_), except that :c:type:`struct fscrypt_context`
-also contains a nonce.  The nonce is randomly generated by the kernel
-and is used to derive the inode's encryption key as described in
-`Per-file keys`_.
+The context structs contain the same information as the corresponding
+policy structs (see `Setting an encryption policy`_), except that the
+context structs also contain a nonce.  The nonce is randomly generated
+by the kernel and is used as KDF input or as a tweak to cause
+different files to be encrypted differently; see `Per-file keys`_ and
+`DIRECT_KEY and per-mode keys`_.
 
 Data path changes
 -----------------

MAINTAINERS

@@ -6662,6 +6662,7 @@ T:	git git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt.git
 S:	Supported
 F:	fs/crypto/
 F:	include/linux/fscrypt*.h
+F:	include/uapi/linux/fscrypt.h
 F:	Documentation/filesystems/fscrypt.rst
 
 FSI SUBSYSTEM

fs/crypto/Kconfig

@@ -7,6 +7,8 @@ config FS_ENCRYPTION
 	select CRYPTO_ECB
 	select CRYPTO_XTS
 	select CRYPTO_CTS
+	select CRYPTO_SHA512
+	select CRYPTO_HMAC
 	select KEYS
 	help
 	  Enable encryption of files and directories.  This

fs/crypto/Makefile

 # SPDX-License-Identifier: GPL-2.0-only
 obj-$(CONFIG_FS_ENCRYPTION)	+= fscrypto.o
 
-fscrypto-y := crypto.o fname.o hooks.o keyinfo.o policy.o
+fscrypto-y := crypto.o \
+	      fname.o \
+	      hkdf.o \
+	      hooks.o \
+	      keyring.o \
+	      keysetup.o \
+	      keysetup_v1.o \
+	      policy.o
+
 fscrypto-$(CONFIG_BLOCK) += bio.o

fs/crypto/crypto.c

@@ -141,7 +141,7 @@ void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
 	memset(iv, 0, ci->ci_mode->ivsize);
 	iv->lblk_num = cpu_to_le64(lblk_num);
 
-	if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY)
+	if (fscrypt_is_direct_key_policy(&ci->ci_policy))
 		memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 
 	if (ci->ci_essiv_tfm != NULL)
@@ -188,10 +188,8 @@ int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
 		res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
 	skcipher_request_free(req);
 	if (res) {
-		fscrypt_err(inode->i_sb,
-			    "%scryption failed for inode %lu, block %llu: %d",
-			    (rw == FS_DECRYPT ? "de" : "en"),
-			    inode->i_ino, lblk_num, res);
+		fscrypt_err(inode, "%scryption failed for block %llu: %d",
+			    (rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
 		return res;
 	}
 	return 0;
@@ -453,7 +451,7 @@ int fscrypt_initialize(unsigned int cop_flags)
 	return res;
 }
 
-void fscrypt_msg(struct super_block *sb, const char *level,
+void fscrypt_msg(const struct inode *inode, const char *level,
 		 const char *fmt, ...)
 {
 	static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
@@ -467,8 +465,9 @@ void fscrypt_msg(struct super_block *sb, const char *level,
 	va_start(args, fmt);
 	vaf.fmt = fmt;
 	vaf.va = &args;
-	if (sb)
-		printk("%sfscrypt (%s): %pV\n", level, sb->s_id, &vaf);
+	if (inode)
+		printk("%sfscrypt (%s, inode %lu): %pV\n",
+		       level, inode->i_sb->s_id, inode->i_ino, &vaf);
 	else
 		printk("%sfscrypt: %pV\n", level, &vaf);
 	va_end(args);
@@ -479,6 +478,8 @@ void fscrypt_msg(struct super_block *sb, const char *level,
  */
 static int __init fscrypt_init(void)
 {
+	int err = -ENOMEM;
+
 	/*
 	 * Use an unbound workqueue to allow bios to be decrypted in parallel
 	 * even when they happen to complete on the same CPU.  This sacrifices
@@ -501,31 +502,19 @@ static int __init fscrypt_init(void)
 	if (!fscrypt_info_cachep)
 		goto fail_free_ctx;
 
+	err = fscrypt_init_keyring();
+	if (err)
+		goto fail_free_info;
+
 	return 0;
 
+fail_free_info:
+	kmem_cache_destroy(fscrypt_info_cachep);
 fail_free_ctx:
 	kmem_cache_destroy(fscrypt_ctx_cachep);
 fail_free_queue:
 	destroy_workqueue(fscrypt_read_workqueue);
 fail:
-	return -ENOMEM;
-}
-module_init(fscrypt_init)
-
-/**
- * fscrypt_exit() - Shutdown the fs encryption system
- */
-static void __exit fscrypt_exit(void)
-{
-	fscrypt_destroy();
-
-	if (fscrypt_read_workqueue)
-		destroy_workqueue(fscrypt_read_workqueue);
-	kmem_cache_destroy(fscrypt_ctx_cachep);
-	kmem_cache_destroy(fscrypt_info_cachep);
-
-	fscrypt_essiv_cleanup();
+	return err;
 }
-module_exit(fscrypt_exit);
-
-MODULE_LICENSE("GPL");
+late_initcall(fscrypt_init)

fs/crypto/fname.c

@@ -71,9 +71,7 @@ int fname_encrypt(struct inode *inode, const struct qstr *iname,
 	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
 	skcipher_request_free(req);
 	if (res < 0) {
-		fscrypt_err(inode->i_sb,
-			    "Filename encryption failed for inode %lu: %d",
-			    inode->i_ino, res);
+		fscrypt_err(inode, "Filename encryption failed: %d", res);
 		return res;
 	}
 
@@ -117,9 +115,7 @@ static int fname_decrypt(struct inode *inode,
 	res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
 	skcipher_request_free(req);
 	if (res < 0) {
-		fscrypt_err(inode->i_sb,
-			    "Filename decryption failed for inode %lu: %d",
-			    inode->i_ino, res);
+		fscrypt_err(inode, "Filename decryption failed: %d", res);
 		return res;
 	}
 
@@ -127,44 +123,45 @@ static int fname_decrypt(struct inode *inode,
 	return 0;
 }
 
-static const char *lookup_table =
+static const char lookup_table[65] =
 	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,";
 
 #define BASE64_CHARS(nbytes)	DIV_ROUND_UP((nbytes) * 4, 3)
 
 /**
- * digest_encode() -
+ * base64_encode() -
  *
- * Encodes the input digest using characters from the set [a-zA-Z0-9_+].
+ * Encodes the input string using characters from the set [A-Za-z0-9+,].
  * The encoded string is roughly 4/3 times the size of the input string.
+ *
+ * Return: length of the encoded string
  */
-static int digest_encode(const char *src, int len, char *dst)
+static int base64_encode(const u8 *src, int len, char *dst)
 {
-	int i = 0, bits = 0, ac = 0;
+	int i, bits = 0, ac = 0;
 	char *cp = dst;
 
-	while (i < len) {
-		ac += (((unsigned char) src[i]) << bits);
+	for (i = 0; i < len; i++) {
+		ac += src[i] << bits;
 		bits += 8;
 		do {
 			*cp++ = lookup_table[ac & 0x3f];
 			ac >>= 6;
 			bits -= 6;
 		} while (bits >= 6);
-		i++;
 	}
 	if (bits)
 		*cp++ = lookup_table[ac & 0x3f];
 	return cp - dst;
 }
 
-static int digest_decode(const char *src, int len, char *dst)
+static int base64_decode(const char *src, int len, u8 *dst)
 {
-	int i = 0, bits = 0, ac = 0;
+	int i, bits = 0, ac = 0;
 	const char *p;
-	char *cp = dst;
+	u8 *cp = dst;
 
-	while (i < len) {
+	for (i = 0; i < len; i++) {
 		p = strchr(lookup_table, src[i]);
 		if (p == NULL || src[i] == 0)
 			return -2;
@@ -175,7 +172,6 @@ static int digest_decode(const char *src, int len, char *dst)
 			ac >>= 8;
 			bits -= 8;
 		}
-		i++;
 	}
 	if (ac)
 		return -1;
@@ -185,8 +181,9 @@ static int digest_decode(const char *src, int len, char *dst)
 bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
 				  u32 max_len, u32 *encrypted_len_ret)
 {
-	int padding = 4 << (inode->i_crypt_info->ci_flags &
-			    FS_POLICY_FLAGS_PAD_MASK);
+	const struct fscrypt_info *ci = inode->i_crypt_info;
+	int padding = 4 << (fscrypt_policy_flags(&ci->ci_policy) &
+			    FSCRYPT_POLICY_FLAGS_PAD_MASK);
 	u32 encrypted_len;
 
 	if (orig_len > max_len)
@@ -272,7 +269,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
 		return fname_decrypt(inode, iname, oname);
 
 	if (iname->len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE) {
-		oname->len = digest_encode(iname->name, iname->len,
+		oname->len = base64_encode(iname->name, iname->len,
 					   oname->name);
 		return 0;
 	}
@@ -287,7 +284,7 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
 	       FSCRYPT_FNAME_DIGEST(iname->name, iname->len),
 	       FSCRYPT_FNAME_DIGEST_SIZE);
 	oname->name[0] = '_';
-	oname->len = 1 + digest_encode((const char *)&digested_name,
+	oname->len = 1 + base64_encode((const u8 *)&digested_name,
 				       sizeof(digested_name), oname->name + 1);
 	return 0;
 }
@@ -380,8 +377,8 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 	if (fname->crypto_buf.name == NULL)
 		return -ENOMEM;
 
-	ret = digest_decode(iname->name + digested, iname->len - digested,
-				fname->crypto_buf.name);
+	ret = base64_decode(iname->name + digested, iname->len - digested,
+			    fname->crypto_buf.name);
 	if (ret < 0) {
 		ret = -ENOENT;
 		goto errout;

fs/crypto/fscrypt_private.h

@@ -4,9 +4,8 @@
  *
  * Copyright (C) 2015, Google, Inc.
  *
- * This contains encryption key functions.
- *
- * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
+ * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
+ * Heavily modified since then.
  */
 
 #ifndef _FSCRYPT_PRIVATE_H
@@ -15,30 +14,133 @@
 #include <linux/fscrypt.h>
 #include <crypto/hash.h>
 
-/* Encryption parameters */
+#define CONST_STRLEN(str)	(sizeof(str) - 1)
+
 #define FS_KEY_DERIVATION_NONCE_SIZE	16
 
-/**
- * Encryption context for inode
- *
- * Protector format:
- *  1 byte: Protector format (1 = this version)
- *  1 byte: File contents encryption mode
- *  1 byte: File names encryption mode
- *  1 byte: Flags
- *  8 bytes: Master Key descriptor
- *  16 bytes: Encryption Key derivation nonce
- */
-struct fscrypt_context {
-	u8 format;
+#define FSCRYPT_MIN_KEY_SIZE		16
+
+#define FSCRYPT_CONTEXT_V1	1
+#define FSCRYPT_CONTEXT_V2	2
+
+struct fscrypt_context_v1 {
+	u8 version; /* FSCRYPT_CONTEXT_V1 */
 	u8 contents_encryption_mode;
 	u8 filenames_encryption_mode;
 	u8 flags;
-	u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+	u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
 	u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
-} __packed;
+};
 
-#define FS_ENCRYPTION_CONTEXT_FORMAT_V1		1
+struct fscrypt_context_v2 {
+	u8 version; /* FSCRYPT_CONTEXT_V2 */
+	u8 contents_encryption_mode;
+	u8 filenames_encryption_mode;
+	u8 flags;
+	u8 __reserved[4];
+	u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+	u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
+};
+
+/**
+ * fscrypt_context - the encryption context of an inode
+ *
+ * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
+ * encrypted file usually in a hidden extended attribute.  It contains the
+ * fields from the fscrypt_policy, in order to identify the encryption algorithm
+ * and key with which the file is encrypted.  It also contains a nonce that was
+ * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
+ * to cause different files to be encrypted differently.
+ */
+union fscrypt_context {
+	u8 version;
+	struct fscrypt_context_v1 v1;
+	struct fscrypt_context_v2 v2;
+};
+
+/*
+ * Return the size expected for the given fscrypt_context based on its version
+ * number, or 0 if the context version is unrecognized.
+ */
+static inline int fscrypt_context_size(const union fscrypt_context *ctx)
+{
+	switch (ctx->version) {
+	case FSCRYPT_CONTEXT_V1:
+		BUILD_BUG_ON(sizeof(ctx->v1) != 28);
+		return sizeof(ctx->v1);
+	case FSCRYPT_CONTEXT_V2:
+		BUILD_BUG_ON(sizeof(ctx->v2) != 40);
+		return sizeof(ctx->v2);
+	}
+	return 0;
+}
+
+#undef fscrypt_policy
+union fscrypt_policy {
+	u8 version;
+	struct fscrypt_policy_v1 v1;
+	struct fscrypt_policy_v2 v2;
+};
+
+/*
+ * Return the size expected for the given fscrypt_policy based on its version
+ * number, or 0 if the policy version is unrecognized.
+ */
+static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return sizeof(policy->v1);
+	case FSCRYPT_POLICY_V2:
+		return sizeof(policy->v2);
+	}
+	return 0;
+}
+
+/* Return the contents encryption mode of a valid encryption policy */
+static inline u8
+fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return policy->v1.contents_encryption_mode;
+	case FSCRYPT_POLICY_V2:
+		return policy->v2.contents_encryption_mode;
+	}
+	BUG();
+}
+
+/* Return the filenames encryption mode of a valid encryption policy */
+static inline u8
+fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return policy->v1.filenames_encryption_mode;
+	case FSCRYPT_POLICY_V2:
+		return policy->v2.filenames_encryption_mode;
+	}
+	BUG();
+}
+
+/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
+static inline u8
+fscrypt_policy_flags(const union fscrypt_policy *policy)
+{
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		return policy->v1.flags;
+	case FSCRYPT_POLICY_V2:
+		return policy->v2.flags;
+	}
+	BUG();
+}
+
+static inline bool
+fscrypt_is_direct_key_policy(const union fscrypt_policy *policy)
+{
+	return fscrypt_policy_flags(policy) & FSCRYPT_POLICY_FLAG_DIRECT_KEY;
+}
 
 /**
  * For encrypted symlinks, the ciphertext length is stored at the beginning
@@ -68,23 +170,37 @@ struct fscrypt_info {
 	struct crypto_cipher *ci_essiv_tfm;
 
 	/*
-	 * Encryption mode used for this inode.  It corresponds to either
-	 * ci_data_mode or ci_filename_mode, depending on the inode type.
+	 * Encryption mode used for this inode.  It corresponds to either the
+	 * contents or filenames encryption mode, depending on the inode type.
 	 */
 	struct fscrypt_mode *ci_mode;
 
+	/* Back-pointer to the inode */
+	struct inode *ci_inode;
+
+	/*
+	 * The master key with which this inode was unlocked (decrypted).  This
+	 * will be NULL if the master key was found in a process-subscribed
+	 * keyring rather than in the filesystem-level keyring.
+	 */
+	struct key *ci_master_key;
+
+	/*
+	 * Link in list of inodes that were unlocked with the master key.
+	 * Only used when ->ci_master_key is set.
+	 */
+	struct list_head ci_master_key_link;
+
 	/*
-	 * If non-NULL, then this inode uses a master key directly rather than a
-	 * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm.
-	 * Otherwise, this inode uses a derived key.
+	 * If non-NULL, then encryption is done using the master key directly
+	 * and ci_ctfm will equal ci_direct_key->dk_ctfm.
 	 */
-	struct fscrypt_master_key *ci_master_key;
+	struct fscrypt_direct_key *ci_direct_key;
 
-	/* fields from the fscrypt_context */
-	u8 ci_data_mode;
-	u8 ci_filename_mode;
-	u8 ci_flags;
-	u8 ci_master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
+	/* The encryption policy used by this inode */
+	union fscrypt_policy ci_policy;
+
+	/* This inode's nonce, copied from the fscrypt_context */
 	u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
 };
 
@@ -98,16 +214,16 @@ typedef enum {
 static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
 					   u32 filenames_mode)
 {
-	if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC &&
-	    filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS)
+	if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
+	    filenames_mode == FSCRYPT_MODE_AES_128_CTS)
 		return true;
 
-	if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS &&
-	    filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS)
+	if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
+	    filenames_mode == FSCRYPT_MODE_AES_256_CTS)
 		return true;
 
-	if (contents_mode == FS_ENCRYPTION_MODE_ADIANTUM &&
-	    filenames_mode == FS_ENCRYPTION_MODE_ADIANTUM)
+	if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
+	    filenames_mode == FSCRYPT_MODE_ADIANTUM)
 		return true;
 
 	return false;
@@ -125,12 +241,12 @@ extern struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
 extern const struct dentry_operations fscrypt_d_ops;
 
 extern void __printf(3, 4) __cold
-fscrypt_msg(struct super_block *sb, const char *level, const char *fmt, ...);
+fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
 
-#define fscrypt_warn(sb, fmt, ...)		\
-	fscrypt_msg(sb, KERN_WARNING, fmt, ##__VA_ARGS__)
-#define fscrypt_err(sb, fmt, ...)		\
-	fscrypt_msg(sb, KERN_ERR, fmt, ##__VA_ARGS__)
+#define fscrypt_warn(inode, fmt, ...)		\
+	fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
+#define fscrypt_err(inode, fmt, ...)		\
+	fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
 
 #define FSCRYPT_MAX_IV_SIZE	32
 
@@ -155,7 +271,172 @@ extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
 					 u32 orig_len, u32 max_len,
 					 u32 *encrypted_len_ret);
 
-/* keyinfo.c */
+/* hkdf.c */
+
+struct fscrypt_hkdf {
+	struct crypto_shash *hmac_tfm;
+};
+
+extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
+			     unsigned int master_key_size);
+
+/*
+ * The list of contexts in which fscrypt uses HKDF.  These values are used as
+ * the first byte of the HKDF application-specific info string to guarantee that
+ * info strings are never repeated between contexts.  This ensures that all HKDF
+ * outputs are unique and cryptographically isolated, i.e. knowledge of one
+ * output doesn't reveal another.
+ */
+#define HKDF_CONTEXT_KEY_IDENTIFIER	1
+#define HKDF_CONTEXT_PER_FILE_KEY	2
+#define HKDF_CONTEXT_PER_MODE_KEY	3
+
+extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
+			       const u8 *info, unsigned int infolen,
+			       u8 *okm, unsigned int okmlen);
+
+extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
+
+/* keyring.c */
+
+/*
+ * fscrypt_master_key_secret - secret key material of an in-use master key
+ */
+struct fscrypt_master_key_secret {
+
+	/*
+	 * For v2 policy keys: HKDF context keyed by this master key.
+	 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
+	 */
+	struct fscrypt_hkdf	hkdf;
+
+	/* Size of the raw key in bytes.  Set even if ->raw isn't set. */
+	u32			size;
+
+	/* For v1 policy keys: the raw key.  Wiped for v2 policy keys. */
+	u8			raw[FSCRYPT_MAX_KEY_SIZE];
+
+} __randomize_layout;
+
+/*
+ * fscrypt_master_key - an in-use master key
+ *
+ * This represents a master encryption key which has been added to the
+ * filesystem and can be used to "unlock" the encrypted files which were
+ * encrypted with it.
+ */
+struct fscrypt_master_key {
+
+	/*
+	 * The secret key material.  After FS_IOC_REMOVE_ENCRYPTION_KEY is
+	 * executed, this is wiped and no new inodes can be unlocked with this
+	 * key; however, there may still be inodes in ->mk_decrypted_inodes
+	 * which could not be evicted.  As long as some inodes still remain,
+	 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
+	 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
+	 *
+	 * Locking: protected by key->sem (outer) and mk_secret_sem (inner).
+	 * The reason for two locks is that key->sem also protects modifying
+	 * mk_users, which ranks it above the semaphore for the keyring key
+	 * type, which is in turn above page faults (via keyring_read).  But
+	 * sometimes filesystems call fscrypt_get_encryption_info() from within
+	 * a transaction, which ranks it below page faults.  So we need a
+	 * separate lock which protects mk_secret but not also mk_users.
+	 */
+	struct fscrypt_master_key_secret	mk_secret;
+	struct rw_semaphore			mk_secret_sem;
+
+	/*
+	 * For v1 policy keys: an arbitrary key descriptor which was assigned by
+	 * userspace (->descriptor).
+	 *
+	 * For v2 policy keys: a cryptographic hash of this key (->identifier).
+	 */
+	struct fscrypt_key_specifier		mk_spec;
+
+	/*
+	 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
+	 * user who has added this key.  Normally each key will be added by just
+	 * one user, but it's possible that multiple users share a key, and in
+	 * that case we need to keep track of those users so that one user can't
+	 * remove the key before the others want it removed too.
+	 *
+	 * This is NULL for v1 policy keys; those can only be added by root.
+	 *
+	 * Locking: in addition to this keyrings own semaphore, this is
+	 * protected by the master key's key->sem, so we can do atomic
+	 * search+insert.  It can also be searched without taking any locks, but
+	 * in that case the returned key may have already been removed.
+	 */
+	struct key		*mk_users;
+
+	/*
+	 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
+	 * Once this goes to 0, the master key is removed from ->s_master_keys.
+	 * The 'struct fscrypt_master_key' will continue to live as long as the
+	 * 'struct key' whose payload it is, but we won't let this reference
+	 * count rise again.
+	 */
+	refcount_t		mk_refcount;
+
+	/*
+	 * List of inodes that were unlocked using this key.  This allows the
+	 * inodes to be evicted efficiently if the key is removed.
+	 */
+	struct list_head	mk_decrypted_inodes;
+	spinlock_t		mk_decrypted_inodes_lock;
+
+	/* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */
+	struct crypto_skcipher	*mk_mode_keys[__FSCRYPT_MODE_MAX + 1];
+
+} __randomize_layout;
+
+static inline bool
+is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
+{
+	/*
+	 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
+	 * fscrypt_key_describe().  These run in atomic context, so they can't
+	 * take ->mk_secret_sem and thus 'secret' can change concurrently which
+	 * would be a data race.  But they only need to know whether the secret
+	 * *was* present at the time of check, so READ_ONCE() suffices.
+	 */
+	return READ_ONCE(secret->size) != 0;
+}
+
+static inline const char *master_key_spec_type(
+				const struct fscrypt_key_specifier *spec)
+{
+	switch (spec->type) {
+	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
+		return "descriptor";
+	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
+		return "identifier";
+	}
+	return "[unknown]";
+}
+
+static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
+{
+	switch (spec->type) {
+	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
+		return FSCRYPT_KEY_DESCRIPTOR_SIZE;
+	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
+		return FSCRYPT_KEY_IDENTIFIER_SIZE;
+	}
+	return 0;
+}
+
+extern struct key *
+fscrypt_find_master_key(struct super_block *sb,
+			const struct fscrypt_key_specifier *mk_spec);
+
+extern int fscrypt_verify_key_added(struct super_block *sb,
+				    const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
+
+extern int __init fscrypt_init_keyring(void);
+
+/* keysetup.c */
 
 struct fscrypt_mode {
 	const char *friendly_name;
@@ -166,6 +447,36 @@ struct fscrypt_mode {
 	bool needs_essiv;
 };
 
-extern void __exit fscrypt_essiv_cleanup(void);
+static inline bool
+fscrypt_mode_supports_direct_key(const struct fscrypt_mode *mode)
+{
+	return mode->ivsize >= offsetofend(union fscrypt_iv, nonce);
+}
+
+extern struct crypto_skcipher *
+fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
+			  const struct inode *inode);
+
+extern int fscrypt_set_derived_key(struct fscrypt_info *ci,
+				   const u8 *derived_key);
+
+/* keysetup_v1.c */
+
+extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
+
+extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
+				     const u8 *raw_master_key);
+
+extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
+					struct fscrypt_info *ci);
+/* policy.c */
+
+extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
+				   const union fscrypt_policy *policy2);
+extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
+				     const struct inode *inode);
+extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
+				       const union fscrypt_context *ctx_u,
+				       int ctx_size);
 
 #endif /* _FSCRYPT_PRIVATE_H */

fs/crypto/hkdf.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of HKDF ("HMAC-based Extract-and-Expand Key Derivation
+ * Function"), aka RFC 5869.  See also the original paper (Krawczyk 2010):
+ * "Cryptographic Extraction and Key Derivation: The HKDF Scheme".
+ *
+ * This is used to derive keys from the fscrypt master keys.
+ *
+ * Copyright 2019 Google LLC
+ */
+
+#include <crypto/hash.h>
+#include <crypto/sha.h>
+
+#include "fscrypt_private.h"
+
+/*
+ * HKDF supports any unkeyed cryptographic hash algorithm, but fscrypt uses
+ * SHA-512 because it is reasonably secure and efficient; and since it produces
+ * a 64-byte digest, deriving an AES-256-XTS key preserves all 64 bytes of
+ * entropy from the master key and requires only one iteration of HKDF-Expand.
+ */
+#define HKDF_HMAC_ALG		"hmac(sha512)"
+#define HKDF_HASHLEN		SHA512_DIGEST_SIZE
+
+/*
+ * HKDF consists of two steps:
+ *
+ * 1. HKDF-Extract: extract a pseudorandom key of length HKDF_HASHLEN bytes from
+ *    the input keying material and optional salt.
+ * 2. HKDF-Expand: expand the pseudorandom key into output keying material of
+ *    any length, parameterized by an application-specific info string.
+ *
+ * HKDF-Extract can be skipped if the input is already a pseudorandom key of
+ * length HKDF_HASHLEN bytes.  However, cipher modes other than AES-256-XTS take
+ * shorter keys, and we don't want to force users of those modes to provide
+ * unnecessarily long master keys.  Thus fscrypt still does HKDF-Extract.  No
+ * salt is used, since fscrypt master keys should already be pseudorandom and
+ * there's no way to persist a random salt per master key from kernel mode.
+ */
+
+/* HKDF-Extract (RFC 5869 section 2.2), unsalted */
+static int hkdf_extract(struct crypto_shash *hmac_tfm, const u8 *ikm,
+			unsigned int ikmlen, u8 prk[HKDF_HASHLEN])
+{
+	static const u8 default_salt[HKDF_HASHLEN];
+	SHASH_DESC_ON_STACK(desc, hmac_tfm);
+	int err;
+
+	err = crypto_shash_setkey(hmac_tfm, default_salt, HKDF_HASHLEN);
+	if (err)
+		return err;
+
+	desc->tfm = hmac_tfm;
+	err = crypto_shash_digest(desc, ikm, ikmlen, prk);
+	shash_desc_zero(desc);
+	return err;
+}
+
+/*
+ * Compute HKDF-Extract using the given master key as the input keying material,
+ * and prepare an HMAC transform object keyed by the resulting pseudorandom key.
+ *
+ * Afterwards, the keyed HMAC transform object can be used for HKDF-Expand many
+ * times without having to recompute HKDF-Extract each time.
+ */
+int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
+		      unsigned int master_key_size)
+{
+	struct crypto_shash *hmac_tfm;
+	u8 prk[HKDF_HASHLEN];
+	int err;
+
+	hmac_tfm = crypto_alloc_shash(HKDF_HMAC_ALG, 0, 0);
+	if (IS_ERR(hmac_tfm)) {
+		fscrypt_err(NULL, "Error allocating " HKDF_HMAC_ALG ": %ld",
+			    PTR_ERR(hmac_tfm));
+		return PTR_ERR(hmac_tfm);
+	}
+
+	if (WARN_ON(crypto_shash_digestsize(hmac_tfm) != sizeof(prk))) {
+		err = -EINVAL;
+		goto err_free_tfm;
+	}
+
+	err = hkdf_extract(hmac_tfm, master_key, master_key_size, prk);
+	if (err)
+		goto err_free_tfm;
+
+	err = crypto_shash_setkey(hmac_tfm, prk, sizeof(prk));
+	if (err)
+		goto err_free_tfm;
+
+	hkdf->hmac_tfm = hmac_tfm;
+	goto out;
+
+err_free_tfm:
+	crypto_free_shash(hmac_tfm);
+out:
+	memzero_explicit(prk, sizeof(prk));
+	return err;
+}
+
+/*
+ * HKDF-Expand (RFC 5869 section 2.3).  This expands the pseudorandom key, which
+ * was already keyed into 'hkdf->hmac_tfm' by fscrypt_init_hkdf(), into 'okmlen'
+ * bytes of output keying material parameterized by the application-specific
+ * 'info' of length 'infolen' bytes, prefixed by "fscrypt\0" and the 'context'
+ * byte.  This is thread-safe and may be called by multiple threads in parallel.
+ *
+ * ('context' isn't part of the HKDF specification; it's just a prefix fscrypt
+ * adds to its application-specific info strings to guarantee that it doesn't
+ * accidentally repeat an info string when using HKDF for different purposes.)
+ */
+int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
+			const u8 *info, unsigned int infolen,
+			u8 *okm, unsigned int okmlen)
+{
+	SHASH_DESC_ON_STACK(desc, hkdf->hmac_tfm);
+	u8 prefix[9];
+	unsigned int i;
+	int err;
+	const u8 *prev = NULL;
+	u8 counter = 1;
+	u8 tmp[HKDF_HASHLEN];
+
+	if (WARN_ON(okmlen > 255 * HKDF_HASHLEN))
+		return -EINVAL;
+
+	desc->tfm = hkdf->hmac_tfm;
+
+	memcpy(prefix, "fscrypt\0", 8);
+	prefix[8] = context;
+
+	for (i = 0; i < okmlen; i += HKDF_HASHLEN) {
+
+		err = crypto_shash_init(desc);
+		if (err)
+			goto out;
+
+		if (prev) {
+			err = crypto_shash_update(desc, prev, HKDF_HASHLEN);
+			if (err)
+				goto out;
+		}
+
+		err = crypto_shash_update(desc, prefix, sizeof(prefix));
+		if (err)
+			goto out;
+
+		err = crypto_shash_update(desc, info, infolen);
+		if (err)
+			goto out;
+
+		BUILD_BUG_ON(sizeof(counter) != 1);
+		if (okmlen - i < HKDF_HASHLEN) {
+			err = crypto_shash_finup(desc, &counter, 1, tmp);
+			if (err)
+				goto out;
+			memcpy(&okm[i], tmp, okmlen - i);
+			memzero_explicit(tmp, sizeof(tmp));
+		} else {
+			err = crypto_shash_finup(desc, &counter, 1, &okm[i]);
+			if (err)
+				goto out;
+		}
+		counter++;
+		prev = &okm[i];
+	}
+	err = 0;
+out:
+	if (unlikely(err))
+		memzero_explicit(okm, okmlen); /* so caller doesn't need to */
+	shash_desc_zero(desc);
+	return err;
+}
+
+void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf)
+{
+	crypto_free_shash(hkdf->hmac_tfm);
+}

fs/crypto/hooks.c

@@ -39,9 +39,9 @@ int fscrypt_file_open(struct inode *inode, struct file *filp)
 	dir = dget_parent(file_dentry(filp));
 	if (IS_ENCRYPTED(d_inode(dir)) &&
 	    !fscrypt_has_permitted_context(d_inode(dir), inode)) {
-		fscrypt_warn(inode->i_sb,
-			     "inconsistent encryption contexts: %lu/%lu",
-			     d_inode(dir)->i_ino, inode->i_ino);
+		fscrypt_warn(inode,
+			     "Inconsistent encryption context (parent directory: %lu)",
+			     d_inode(dir)->i_ino);
 		err = -EPERM;
 	}
 	dput(dir);

fs/crypto/keyring.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Filesystem-level keyring for fscrypt
+ *
+ * Copyright 2019 Google LLC
+ */
+
+/*
+ * This file implements management of fscrypt master keys in the
+ * filesystem-level keyring, including the ioctls:
+ *
+ * - FS_IOC_ADD_ENCRYPTION_KEY
+ * - FS_IOC_REMOVE_ENCRYPTION_KEY
+ * - FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
+ * - FS_IOC_GET_ENCRYPTION_KEY_STATUS
+ *
+ * See the "User API" section of Documentation/filesystems/fscrypt.rst for more
+ * information about these ioctls.
+ */
+
+#include <crypto/skcipher.h>
+#include <linux/key-type.h>
+#include <linux/seq_file.h>
+
+#include "fscrypt_private.h"
+
+static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret)
+{
+	fscrypt_destroy_hkdf(&secret->hkdf);
+	memzero_explicit(secret, sizeof(*secret));
+}
+
+static void move_master_key_secret(struct fscrypt_master_key_secret *dst,
+				   struct fscrypt_master_key_secret *src)
+{
+	memcpy(dst, src, sizeof(*dst));
+	memzero_explicit(src, sizeof(*src));
+}
+
+static void free_master_key(struct fscrypt_master_key *mk)
+{
+	size_t i;
+
+	wipe_master_key_secret(&mk->mk_secret);
+
+	for (i = 0; i < ARRAY_SIZE(mk->mk_mode_keys); i++)
+		crypto_free_skcipher(mk->mk_mode_keys[i]);
+
+	key_put(mk->mk_users);
+	kzfree(mk);
+}
+
+static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec)
+{
+	if (spec->__reserved)
+		return false;
+	return master_key_spec_len(spec) != 0;
+}
+
+static int fscrypt_key_instantiate(struct key *key,
+				   struct key_preparsed_payload *prep)
+{
+	key->payload.data[0] = (struct fscrypt_master_key *)prep->data;
+	return 0;
+}
+
+static void fscrypt_key_destroy(struct key *key)
+{
+	free_master_key(key->payload.data[0]);
+}
+
+static void fscrypt_key_describe(const struct key *key, struct seq_file *m)
+{
+	seq_puts(m, key->description);
+
+	if (key_is_positive(key)) {
+		const struct fscrypt_master_key *mk = key->payload.data[0];
+
+		if (!is_master_key_secret_present(&mk->mk_secret))
+			seq_puts(m, ": secret removed");
+	}
+}
+
+/*
+ * Type of key in ->s_master_keys.  Each key of this type represents a master
+ * key which has been added to the filesystem.  Its payload is a
+ * 'struct fscrypt_master_key'.  The "." prefix in the key type name prevents
+ * users from adding keys of this type via the keyrings syscalls rather than via
+ * the intended method of FS_IOC_ADD_ENCRYPTION_KEY.
+ */
+static struct key_type key_type_fscrypt = {
+	.name			= "._fscrypt",
+	.instantiate		= fscrypt_key_instantiate,
+	.destroy		= fscrypt_key_destroy,
+	.describe		= fscrypt_key_describe,
+};
+
+static int fscrypt_user_key_instantiate(struct key *key,
+					struct key_preparsed_payload *prep)
+{
+	/*
+	 * We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for
+	 * each key, regardless of the exact key size.  The amount of memory
+	 * actually used is greater than the size of the raw key anyway.
+	 */
+	return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE);
+}
+
+static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m)
+{
+	seq_puts(m, key->description);
+}
+
+/*
+ * Type of key in ->mk_users.  Each key of this type represents a particular
+ * user who has added a particular master key.
+ *
+ * Note that the name of this key type really should be something like
+ * ".fscrypt-user" instead of simply ".fscrypt".  But the shorter name is chosen
+ * mainly for simplicity of presentation in /proc/keys when read by a non-root
+ * user.  And it is expected to be rare that a key is actually added by multiple
+ * users, since users should keep their encryption keys confidential.
+ */
+static struct key_type key_type_fscrypt_user = {
+	.name			= ".fscrypt",
+	.instantiate		= fscrypt_user_key_instantiate,
+	.describe		= fscrypt_user_key_describe,
+};
+
+/* Search ->s_master_keys or ->mk_users */
+static struct key *search_fscrypt_keyring(struct key *keyring,
+					  struct key_type *type,
+					  const char *description)
+{
+	/*
+	 * We need to mark the keyring reference as "possessed" so that we
+	 * acquire permission to search it, via the KEY_POS_SEARCH permission.
+	 */
+	key_ref_t keyref = make_key_ref(keyring, true /* possessed */);
+
+	keyref = keyring_search(keyref, type, description, false);
+	if (IS_ERR(keyref)) {
+		if (PTR_ERR(keyref) == -EAGAIN || /* not found */
+		    PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */
+			keyref = ERR_PTR(-ENOKEY);
+		return ERR_CAST(keyref);
+	}
+	return key_ref_to_ptr(keyref);
+}
+
+#define FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE	\
+	(CONST_STRLEN("fscrypt-") + FIELD_SIZEOF(struct super_block, s_id))
+
+#define FSCRYPT_MK_DESCRIPTION_SIZE	(2 * FSCRYPT_KEY_IDENTIFIER_SIZE + 1)
+
+#define FSCRYPT_MK_USERS_DESCRIPTION_SIZE	\
+	(CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \
+	 CONST_STRLEN("-users") + 1)
+
+#define FSCRYPT_MK_USER_DESCRIPTION_SIZE	\
+	(2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1)
+
+static void format_fs_keyring_description(
+			char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE],
+			const struct super_block *sb)
+{
+	sprintf(description, "fscrypt-%s", sb->s_id);
+}
+
+static void format_mk_description(
+			char description[FSCRYPT_MK_DESCRIPTION_SIZE],
+			const struct fscrypt_key_specifier *mk_spec)
+{
+	sprintf(description, "%*phN",
+		master_key_spec_len(mk_spec), (u8 *)&mk_spec->u);
+}
+
+static void format_mk_users_keyring_description(
+			char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE],
+			const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
+{
+	sprintf(description, "fscrypt-%*phN-users",
+		FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier);
+}
+
+static void format_mk_user_description(
+			char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE],
+			const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
+{
+
+	sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE,
+		mk_identifier, __kuid_val(current_fsuid()));
+}
+
+/* Create ->s_master_keys if needed.  Synchronized by fscrypt_add_key_mutex. */
+static int allocate_filesystem_keyring(struct super_block *sb)
+{
+	char description[FSCRYPT_FS_KEYRING_DESCRIPTION_SIZE];
+	struct key *keyring;
+
+	if (sb->s_master_keys)
+		return 0;
+
+	format_fs_keyring_description(description, sb);
+	keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+				current_cred(), KEY_POS_SEARCH |
+				  KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
+				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	/* Pairs with READ_ONCE() in fscrypt_find_master_key() */
+	smp_store_release(&sb->s_master_keys, keyring);
+	return 0;
+}
+
+void fscrypt_sb_free(struct super_block *sb)
+{
+	key_put(sb->s_master_keys);
+	sb->s_master_keys = NULL;
+}
+
+/*
+ * Find the specified master key in ->s_master_keys.
+ * Returns ERR_PTR(-ENOKEY) if not found.
+ */
+struct key *fscrypt_find_master_key(struct super_block *sb,
+				    const struct fscrypt_key_specifier *mk_spec)
+{
+	struct key *keyring;
+	char description[FSCRYPT_MK_DESCRIPTION_SIZE];
+
+	/* pairs with smp_store_release() in allocate_filesystem_keyring() */
+	keyring = READ_ONCE(sb->s_master_keys);
+	if (keyring == NULL)
+		return ERR_PTR(-ENOKEY); /* No keyring yet, so no keys yet. */
+
+	format_mk_description(description, mk_spec);
+	return search_fscrypt_keyring(keyring, &key_type_fscrypt, description);
+}
+
+static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk)
+{
+	char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE];
+	struct key *keyring;
+
+	format_mk_users_keyring_description(description,
+					    mk->mk_spec.u.identifier);
+	keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+				current_cred(), KEY_POS_SEARCH |
+				  KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
+				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
+	if (IS_ERR(keyring))
+		return PTR_ERR(keyring);
+
+	mk->mk_users = keyring;
+	return 0;
+}
+
+/*
+ * Find the current user's "key" in the master key's ->mk_users.
+ * Returns ERR_PTR(-ENOKEY) if not found.
+ */
+static struct key *find_master_key_user(struct fscrypt_master_key *mk)
+{
+	char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
+
+	format_mk_user_description(description, mk->mk_spec.u.identifier);
+	return search_fscrypt_keyring(mk->mk_users, &key_type_fscrypt_user,
+				      description);
+}
+
+/*
+ * Give the current user a "key" in ->mk_users.  This charges the user's quota
+ * and marks the master key as added by the current user, so that it cannot be
+ * removed by another user with the key.  Either the master key's key->sem must
+ * be held for write, or the master key must be still undergoing initialization.
+ */
+static int add_master_key_user(struct fscrypt_master_key *mk)
+{
+	char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
+	struct key *mk_user;
+	int err;
+
+	format_mk_user_description(description, mk->mk_spec.u.identifier);
+	mk_user = key_alloc(&key_type_fscrypt_user, description,
+			    current_fsuid(), current_gid(), current_cred(),
+			    KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL);
+	if (IS_ERR(mk_user))
+		return PTR_ERR(mk_user);
+
+	err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL);
+	key_put(mk_user);
+	return err;
+}
+
+/*
+ * Remove the current user's "key" from ->mk_users.
+ * The master key's key->sem must be held for write.
+ *
+ * Returns 0 if removed, -ENOKEY if not found, or another -errno code.
+ */
+static int remove_master_key_user(struct fscrypt_master_key *mk)
+{
+	struct key *mk_user;
+	int err;
+
+	mk_user = find_master_key_user(mk);
+	if (IS_ERR(mk_user))
+		return PTR_ERR(mk_user);
+	err = key_unlink(mk->mk_users, mk_user);
+	key_put(mk_user);
+	return err;
+}
+
+/*
+ * Allocate a new fscrypt_master_key which contains the given secret, set it as
+ * the payload of a new 'struct key' of type fscrypt, and link the 'struct key'
+ * into the given keyring.  Synchronized by fscrypt_add_key_mutex.
+ */
+static int add_new_master_key(struct fscrypt_master_key_secret *secret,
+			      const struct fscrypt_key_specifier *mk_spec,
+			      struct key *keyring)
+{
+	struct fscrypt_master_key *mk;
+	char description[FSCRYPT_MK_DESCRIPTION_SIZE];
+	struct key *key;
+	int err;
+
+	mk = kzalloc(sizeof(*mk), GFP_KERNEL);
+	if (!mk)
+		return -ENOMEM;
+
+	mk->mk_spec = *mk_spec;
+
+	move_master_key_secret(&mk->mk_secret, secret);
+	init_rwsem(&mk->mk_secret_sem);
+
+	refcount_set(&mk->mk_refcount, 1); /* secret is present */
+	INIT_LIST_HEAD(&mk->mk_decrypted_inodes);
+	spin_lock_init(&mk->mk_decrypted_inodes_lock);
+
+	if (mk_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
+		err = allocate_master_key_users_keyring(mk);
+		if (err)
+			goto out_free_mk;
+		err = add_master_key_user(mk);
+		if (err)
+			goto out_free_mk;
+	}
+
+	/*
+	 * Note that we don't charge this key to anyone's quota, since when
+	 * ->mk_users is in use those keys are charged instead, and otherwise
+	 * (when ->mk_users isn't in use) only root can add these keys.
+	 */
+	format_mk_description(description, mk_spec);
+	key = key_alloc(&key_type_fscrypt, description,
+			GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, current_cred(),
+			KEY_POS_SEARCH | KEY_USR_SEARCH | KEY_USR_VIEW,
+			KEY_ALLOC_NOT_IN_QUOTA, NULL);
+	if (IS_ERR(key)) {
+		err = PTR_ERR(key);
+		goto out_free_mk;
+	}
+	err = key_instantiate_and_link(key, mk, sizeof(*mk), keyring, NULL);
+	key_put(key);
+	if (err)
+		goto out_free_mk;
+
+	return 0;
+
+out_free_mk:
+	free_master_key(mk);
+	return err;
+}
+
+#define KEY_DEAD	1
+
+static int add_existing_master_key(struct fscrypt_master_key *mk,
+				   struct fscrypt_master_key_secret *secret)
+{
+	struct key *mk_user;
+	bool rekey;
+	int err;
+
+	/*
+	 * If the current user is already in ->mk_users, then there's nothing to
+	 * do.  (Not applicable for v1 policy keys, which have NULL ->mk_users.)
+	 */
+	if (mk->mk_users) {
+		mk_user = find_master_key_user(mk);
+		if (mk_user != ERR_PTR(-ENOKEY)) {
+			if (IS_ERR(mk_user))
+				return PTR_ERR(mk_user);
+			key_put(mk_user);
+			return 0;
+		}
+	}
+
+	/* If we'll be re-adding ->mk_secret, try to take the reference. */
+	rekey = !is_master_key_secret_present(&mk->mk_secret);
+	if (rekey && !refcount_inc_not_zero(&mk->mk_refcount))
+		return KEY_DEAD;
+
+	/* Add the current user to ->mk_users, if applicable. */
+	if (mk->mk_users) {
+		err = add_master_key_user(mk);
+		if (err) {
+			if (rekey && refcount_dec_and_test(&mk->mk_refcount))
+				return KEY_DEAD;
+			return err;
+		}
+	}
+
+	/* Re-add the secret if needed. */
+	if (rekey) {
+		down_write(&mk->mk_secret_sem);
+		move_master_key_secret(&mk->mk_secret, secret);
+		up_write(&mk->mk_secret_sem);
+	}
+	return 0;
+}
+
+static int add_master_key(struct super_block *sb,
+			  struct fscrypt_master_key_secret *secret,
+			  const struct fscrypt_key_specifier *mk_spec)
+{
+	static DEFINE_MUTEX(fscrypt_add_key_mutex);
+	struct key *key;
+	int err;
+
+	mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */
+retry:
+	key = fscrypt_find_master_key(sb, mk_spec);
+	if (IS_ERR(key)) {
+		err = PTR_ERR(key);
+		if (err != -ENOKEY)
+			goto out_unlock;
+		/* Didn't find the key in ->s_master_keys.  Add it. */
+		err = allocate_filesystem_keyring(sb);
+		if (err)
+			goto out_unlock;
+		err = add_new_master_key(secret, mk_spec, sb->s_master_keys);
+	} else {
+		/*
+		 * Found the key in ->s_master_keys.  Re-add the secret if
+		 * needed, and add the user to ->mk_users if needed.
+		 */
+		down_write(&key->sem);
+		err = add_existing_master_key(key->payload.data[0], secret);
+		up_write(&key->sem);
+		if (err == KEY_DEAD) {
+			/* Key being removed or needs to be removed */
+			key_invalidate(key);
+			key_put(key);
+			goto retry;
+		}
+		key_put(key);
+	}
+out_unlock:
+	mutex_unlock(&fscrypt_add_key_mutex);
+	return err;
+}
+
+/*
+ * Add a master encryption key to the filesystem, causing all files which were
+ * encrypted with it to appear "unlocked" (decrypted) when accessed.
+ *
+ * When adding a key for use by v1 encryption policies, this ioctl is
+ * privileged, and userspace must provide the 'key_descriptor'.
+ *
+ * When adding a key for use by v2+ encryption policies, this ioctl is
+ * unprivileged.  This is needed, in general, to allow non-root users to use
+ * encryption without encountering the visibility problems of process-subscribed
+ * keyrings and the inability to properly remove keys.  This works by having
+ * each key identified by its cryptographically secure hash --- the
+ * 'key_identifier'.  The cryptographic hash ensures that a malicious user
+ * cannot add the wrong key for a given identifier.  Furthermore, each added key
+ * is charged to the appropriate user's quota for the keyrings service, which
+ * prevents a malicious user from adding too many keys.  Finally, we forbid a
+ * user from removing a key while other users have added it too, which prevents
+ * a user who knows another user's key from causing a denial-of-service by
+ * removing it at an inopportune time.  (We tolerate that a user who knows a key
+ * can prevent other users from removing it.)
+ *
+ * For more details, see the "FS_IOC_ADD_ENCRYPTION_KEY" section of
+ * Documentation/filesystems/fscrypt.rst.
+ */
+int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
+{
+	struct super_block *sb = file_inode(filp)->i_sb;
+	struct fscrypt_add_key_arg __user *uarg = _uarg;
+	struct fscrypt_add_key_arg arg;
+	struct fscrypt_master_key_secret secret;
+	int err;
+
+	if (copy_from_user(&arg, uarg, sizeof(arg)))
+		return -EFAULT;
+
+	if (!valid_key_spec(&arg.key_spec))
+		return -EINVAL;
+
+	if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE ||
+	    arg.raw_size > FSCRYPT_MAX_KEY_SIZE)
+		return -EINVAL;
+
+	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
+		return -EINVAL;
+
+	memset(&secret, 0, sizeof(secret));
+	secret.size = arg.raw_size;
+	err = -EFAULT;
+	if (copy_from_user(secret.raw, uarg->raw, secret.size))
+		goto out_wipe_secret;
+
+	switch (arg.key_spec.type) {
+	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
+		/*
+		 * Only root can add keys that are identified by an arbitrary
+		 * descriptor rather than by a cryptographic hash --- since
+		 * otherwise a malicious user could add the wrong key.
+		 */
+		err = -EACCES;
+		if (!capable(CAP_SYS_ADMIN))
+			goto out_wipe_secret;
+		break;
+	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
+		err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size);
+		if (err)
+			goto out_wipe_secret;
+
+		/*
+		 * Now that the HKDF context is initialized, the raw key is no
+		 * longer needed.
+		 */
+		memzero_explicit(secret.raw, secret.size);
+
+		/* Calculate the key identifier and return it to userspace. */
+		err = fscrypt_hkdf_expand(&secret.hkdf,
+					  HKDF_CONTEXT_KEY_IDENTIFIER,
+					  NULL, 0, arg.key_spec.u.identifier,
+					  FSCRYPT_KEY_IDENTIFIER_SIZE);
+		if (err)
+			goto out_wipe_secret;
+		err = -EFAULT;
+		if (copy_to_user(uarg->key_spec.u.identifier,
+				 arg.key_spec.u.identifier,
+				 FSCRYPT_KEY_IDENTIFIER_SIZE))
+			goto out_wipe_secret;
+		break;
+	default:
+		WARN_ON(1);
+		err = -EINVAL;
+		goto out_wipe_secret;
+	}
+
+	err = add_master_key(sb, &secret, &arg.key_spec);
+out_wipe_secret:
+	wipe_master_key_secret(&secret);
+	return err;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
+
+/*
+ * Verify that the current user has added a master key with the given identifier
+ * (returns -ENOKEY if not).  This is needed to prevent a user from encrypting
+ * their files using some other user's key which they don't actually know.
+ * Cryptographically this isn't much of a problem, but the semantics of this
+ * would be a bit weird, so it's best to just forbid it.
+ *
+ * The system administrator (CAP_FOWNER) can override this, which should be
+ * enough for any use cases where encryption policies are being set using keys
+ * that were chosen ahead of time but aren't available at the moment.
+ *
+ * Note that the key may have already removed by the time this returns, but
+ * that's okay; we just care whether the key was there at some point.
+ *
+ * Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code
+ */
+int fscrypt_verify_key_added(struct super_block *sb,
+			     const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
+{
+	struct fscrypt_key_specifier mk_spec;
+	struct key *key, *mk_user;
+	struct fscrypt_master_key *mk;
+	int err;
+
+	mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+	memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
+
+	key = fscrypt_find_master_key(sb, &mk_spec);
+	if (IS_ERR(key)) {
+		err = PTR_ERR(key);
+		goto out;
+	}
+	mk = key->payload.data[0];
+	mk_user = find_master_key_user(mk);
+	if (IS_ERR(mk_user)) {
+		err = PTR_ERR(mk_user);
+	} else {
+		key_put(mk_user);
+		err = 0;
+	}
+	key_put(key);
+out:
+	if (err == -ENOKEY && capable(CAP_FOWNER))
+		err = 0;
+	return err;
+}
+
+/*
+ * Try to evict the inode's dentries from the dentry cache.  If the inode is a
+ * directory, then it can have at most one dentry; however, that dentry may be
+ * pinned by child dentries, so first try to evict the children too.
+ */
+static void shrink_dcache_inode(struct inode *inode)
+{
+	struct dentry *dentry;
+
+	if (S_ISDIR(inode->i_mode)) {
+		dentry = d_find_any_alias(inode);
+		if (dentry) {
+			shrink_dcache_parent(dentry);
+			dput(dentry);
+		}
+	}
+	d_prune_aliases(inode);
+}
+
+static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk)
+{
+	struct fscrypt_info *ci;
+	struct inode *inode;
+	struct inode *toput_inode = NULL;
+
+	spin_lock(&mk->mk_decrypted_inodes_lock);
+
+	list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) {
+		inode = ci->ci_inode;
+		spin_lock(&inode->i_lock);
+		if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&mk->mk_decrypted_inodes_lock);
+
+		shrink_dcache_inode(inode);
+		iput(toput_inode);
+		toput_inode = inode;
+
+		spin_lock(&mk->mk_decrypted_inodes_lock);
+	}
+
+	spin_unlock(&mk->mk_decrypted_inodes_lock);
+	iput(toput_inode);
+}
+
+static int check_for_busy_inodes(struct super_block *sb,
+				 struct fscrypt_master_key *mk)
+{
+	struct list_head *pos;
+	size_t busy_count = 0;
+	unsigned long ino;
+	struct dentry *dentry;
+	char _path[256];
+	char *path = NULL;
+
+	spin_lock(&mk->mk_decrypted_inodes_lock);
+
+	list_for_each(pos, &mk->mk_decrypted_inodes)
+		busy_count++;
+
+	if (busy_count == 0) {
+		spin_unlock(&mk->mk_decrypted_inodes_lock);
+		return 0;
+	}
+
+	{
+		/* select an example file to show for debugging purposes */
+		struct inode *inode =
+			list_first_entry(&mk->mk_decrypted_inodes,
+					 struct fscrypt_info,
+					 ci_master_key_link)->ci_inode;
+		ino = inode->i_ino;
+		dentry = d_find_alias(inode);
+	}
+	spin_unlock(&mk->mk_decrypted_inodes_lock);
+
+	if (dentry) {
+		path = dentry_path(dentry, _path, sizeof(_path));
+		dput(dentry);
+	}
+	if (IS_ERR_OR_NULL(path))
+		path = "(unknown)";
+
+	fscrypt_warn(NULL,
+		     "%s: %zu inode(s) still busy after removing key with %s %*phN, including ino %lu (%s)",
+		     sb->s_id, busy_count, master_key_spec_type(&mk->mk_spec),
+		     master_key_spec_len(&mk->mk_spec), (u8 *)&mk->mk_spec.u,
+		     ino, path);
+	return -EBUSY;
+}
+
+static int try_to_lock_encrypted_files(struct super_block *sb,
+				       struct fscrypt_master_key *mk)
+{
+	int err1;
+	int err2;
+
+	/*
+	 * An inode can't be evicted while it is dirty or has dirty pages.
+	 * Thus, we first have to clean the inodes in ->mk_decrypted_inodes.
+	 *
+	 * Just do it the easy way: call sync_filesystem().  It's overkill, but
+	 * it works, and it's more important to minimize the amount of caches we
+	 * drop than the amount of data we sync.  Also, unprivileged users can
+	 * already call sync_filesystem() via sys_syncfs() or sys_sync().
+	 */
+	down_read(&sb->s_umount);
+	err1 = sync_filesystem(sb);
+	up_read(&sb->s_umount);
+	/* If a sync error occurs, still try to evict as much as possible. */
+
+	/*
+	 * Inodes are pinned by their dentries, so we have to evict their
+	 * dentries.  shrink_dcache_sb() would suffice, but would be overkill
+	 * and inappropriate for use by unprivileged users.  So instead go
+	 * through the inodes' alias lists and try to evict each dentry.
+	 */
+	evict_dentries_for_decrypted_inodes(mk);
+
+	/*
+	 * evict_dentries_for_decrypted_inodes() already iput() each inode in
+	 * the list; any inodes for which that dropped the last reference will
+	 * have been evicted due to fscrypt_drop_inode() detecting the key
+	 * removal and telling the VFS to evict the inode.  So to finish, we
+	 * just need to check whether any inodes couldn't be evicted.
+	 */
+	err2 = check_for_busy_inodes(sb, mk);
+
+	return err1 ?: err2;
+}
+
+/*
+ * Try to remove an fscrypt master encryption key.
+ *
+ * FS_IOC_REMOVE_ENCRYPTION_KEY (all_users=false) removes the current user's
+ * claim to the key, then removes the key itself if no other users have claims.
+ * FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS (all_users=true) always removes the
+ * key itself.
+ *
+ * To "remove the key itself", first we wipe the actual master key secret, so
+ * that no more inodes can be unlocked with it.  Then we try to evict all cached
+ * inodes that had been unlocked with the key.
+ *
+ * If all inodes were evicted, then we unlink the fscrypt_master_key from the
+ * keyring.  Otherwise it remains in the keyring in the "incompletely removed"
+ * state (without the actual secret key) where it tracks the list of remaining
+ * inodes.  Userspace can execute the ioctl again later to retry eviction, or
+ * alternatively can re-add the secret key again.
+ *
+ * For more details, see the "Removing keys" section of
+ * Documentation/filesystems/fscrypt.rst.
+ */
+static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users)
+{
+	struct super_block *sb = file_inode(filp)->i_sb;
+	struct fscrypt_remove_key_arg __user *uarg = _uarg;
+	struct fscrypt_remove_key_arg arg;
+	struct key *key;
+	struct fscrypt_master_key *mk;
+	u32 status_flags = 0;
+	int err;
+	bool dead;
+
+	if (copy_from_user(&arg, uarg, sizeof(arg)))
+		return -EFAULT;
+
+	if (!valid_key_spec(&arg.key_spec))
+		return -EINVAL;
+
+	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
+		return -EINVAL;
+
+	/*
+	 * Only root can add and remove keys that are identified by an arbitrary
+	 * descriptor rather than by a cryptographic hash.
+	 */
+	if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EACCES;
+
+	/* Find the key being removed. */
+	key = fscrypt_find_master_key(sb, &arg.key_spec);
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+	mk = key->payload.data[0];
+
+	down_write(&key->sem);
+
+	/* If relevant, remove current user's (or all users) claim to the key */
+	if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) {
+		if (all_users)
+			err = keyring_clear(mk->mk_users);
+		else
+			err = remove_master_key_user(mk);
+		if (err) {
+			up_write(&key->sem);
+			goto out_put_key;
+		}
+		if (mk->mk_users->keys.nr_leaves_on_tree != 0) {
+			/*
+			 * Other users have still added the key too.  We removed
+			 * the current user's claim to the key, but we still
+			 * can't remove the key itself.
+			 */
+			status_flags |=
+				FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS;
+			err = 0;
+			up_write(&key->sem);
+			goto out_put_key;
+		}
+	}
+
+	/* No user claims remaining.  Go ahead and wipe the secret. */
+	dead = false;
+	if (is_master_key_secret_present(&mk->mk_secret)) {
+		down_write(&mk->mk_secret_sem);
+		wipe_master_key_secret(&mk->mk_secret);
+		dead = refcount_dec_and_test(&mk->mk_refcount);
+		up_write(&mk->mk_secret_sem);
+	}
+	up_write(&key->sem);
+	if (dead) {
+		/*
+		 * No inodes reference the key, and we wiped the secret, so the
+		 * key object is free to be removed from the keyring.
+		 */
+		key_invalidate(key);
+		err = 0;
+	} else {
+		/* Some inodes still reference this key; try to evict them. */
+		err = try_to_lock_encrypted_files(sb, mk);
+		if (err == -EBUSY) {
+			status_flags |=
+				FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY;
+			err = 0;
+		}
+	}
+	/*
+	 * We return 0 if we successfully did something: removed a claim to the
+	 * key, wiped the secret, or tried locking the files again.  Users need
+	 * to check the informational status flags if they care whether the key
+	 * has been fully removed including all files locked.
+	 */
+out_put_key:
+	key_put(key);
+	if (err == 0)
+		err = put_user(status_flags, &uarg->removal_status_flags);
+	return err;
+}
+
+int fscrypt_ioctl_remove_key(struct file *filp, void __user *uarg)
+{
+	return do_remove_key(filp, uarg, false);
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);
+
+int fscrypt_ioctl_remove_key_all_users(struct file *filp, void __user *uarg)
+{
+	if (!capable(CAP_SYS_ADMIN))
+		return -EACCES;
+	return do_remove_key(filp, uarg, true);
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key_all_users);
+
+/*
+ * Retrieve the status of an fscrypt master encryption key.
+ *
+ * We set ->status to indicate whether the key is absent, present, or
+ * incompletely removed.  "Incompletely removed" means that the master key
+ * secret has been removed, but some files which had been unlocked with it are
+ * still in use.  This field allows applications to easily determine the state
+ * of an encrypted directory without using a hack such as trying to open a
+ * regular file in it (which can confuse the "incompletely removed" state with
+ * absent or present).
+ *
+ * In addition, for v2 policy keys we allow applications to determine, via
+ * ->status_flags and ->user_count, whether the key has been added by the
+ * current user, by other users, or by both.  Most applications should not need
+ * this, since ordinarily only one user should know a given key.  However, if a
+ * secret key is shared by multiple users, applications may wish to add an
+ * already-present key to prevent other users from removing it.  This ioctl can
+ * be used to check whether that really is the case before the work is done to
+ * add the key --- which might e.g. require prompting the user for a passphrase.
+ *
+ * For more details, see the "FS_IOC_GET_ENCRYPTION_KEY_STATUS" section of
+ * Documentation/filesystems/fscrypt.rst.
+ */
+int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
+{
+	struct super_block *sb = file_inode(filp)->i_sb;
+	struct fscrypt_get_key_status_arg arg;
+	struct key *key;
+	struct fscrypt_master_key *mk;
+	int err;
+
+	if (copy_from_user(&arg, uarg, sizeof(arg)))
+		return -EFAULT;
+
+	if (!valid_key_spec(&arg.key_spec))
+		return -EINVAL;
+
+	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
+		return -EINVAL;
+
+	arg.status_flags = 0;
+	arg.user_count = 0;
+	memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved));
+
+	key = fscrypt_find_master_key(sb, &arg.key_spec);
+	if (IS_ERR(key)) {
+		if (key != ERR_PTR(-ENOKEY))
+			return PTR_ERR(key);
+		arg.status = FSCRYPT_KEY_STATUS_ABSENT;
+		err = 0;
+		goto out;
+	}
+	mk = key->payload.data[0];
+	down_read(&key->sem);
+
+	if (!is_master_key_secret_present(&mk->mk_secret)) {
+		arg.status = FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED;
+		err = 0;
+		goto out_release_key;
+	}
+
+	arg.status = FSCRYPT_KEY_STATUS_PRESENT;
+	if (mk->mk_users) {
+		struct key *mk_user;
+
+		arg.user_count = mk->mk_users->keys.nr_leaves_on_tree;
+		mk_user = find_master_key_user(mk);
+		if (!IS_ERR(mk_user)) {
+			arg.status_flags |=
+				FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF;
+			key_put(mk_user);
+		} else if (mk_user != ERR_PTR(-ENOKEY)) {
+			err = PTR_ERR(mk_user);
+			goto out_release_key;
+		}
+	}
+	err = 0;
+out_release_key:
+	up_read(&key->sem);
+	key_put(key);
+out:
+	if (!err && copy_to_user(uarg, &arg, sizeof(arg)))
+		err = -EFAULT;
+	return err;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status);
+
+int __init fscrypt_init_keyring(void)
+{
+	int err;
+
+	err = register_key_type(&key_type_fscrypt);
+	if (err)
+		return err;
+
+	err = register_key_type(&key_type_fscrypt_user);
+	if (err)
+		goto err_unregister_fscrypt;
+
+	return 0;
+
+err_unregister_fscrypt:
+	unregister_key_type(&key_type_fscrypt);
+	return err;
+}

fs/crypto/keyinfo.c → fs/crypto/keysetup.c

 // SPDX-License-Identifier: GPL-2.0
 /*
- * key management facility for FS encryption support.
+ * Key setup facility for FS encryption support.
  *
  * Copyright (C) 2015, Google, Inc.
  *
- * This contains encryption key functions.
- *
- * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
+ * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
+ * Heavily modified since then.
  */
 
-#include <keys/user-type.h>
-#include <linux/hashtable.h>
-#include <linux/scatterlist.h>
 #include <crypto/aes.h>
-#include <crypto/algapi.h>
 #include <crypto/sha.h>
 #include <crypto/skcipher.h>
+#include <linux/key.h>
+
 #include "fscrypt_private.h"
 
 static struct crypto_shash *essiv_hash_tfm;
 
-/* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */
-static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */
-static DEFINE_SPINLOCK(fscrypt_master_keys_lock);
-
-/*
- * Key derivation function.  This generates the derived key by encrypting the
- * master key with AES-128-ECB using the inode's nonce as the AES key.
- *
- * The master key must be at least as long as the derived key.  If the master
- * key is longer, then only the first 'derived_keysize' bytes are used.
- */
-static int derive_key_aes(const u8 *master_key,
-			  const struct fscrypt_context *ctx,
-			  u8 *derived_key, unsigned int derived_keysize)
-{
-	int res = 0;
-	struct skcipher_request *req = NULL;
-	DECLARE_CRYPTO_WAIT(wait);
-	struct scatterlist src_sg, dst_sg;
-	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
-
-	if (IS_ERR(tfm)) {
-		res = PTR_ERR(tfm);
-		tfm = NULL;
-		goto out;
-	}
-	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
-	req = skcipher_request_alloc(tfm, GFP_NOFS);
-	if (!req) {
-		res = -ENOMEM;
-		goto out;
-	}
-	skcipher_request_set_callback(req,
-			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
-			crypto_req_done, &wait);
-	res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce));
-	if (res < 0)
-		goto out;
-
-	sg_init_one(&src_sg, master_key, derived_keysize);
-	sg_init_one(&dst_sg, derived_key, derived_keysize);
-	skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
-				   NULL);
-	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
-out:
-	skcipher_request_free(req);
-	crypto_free_skcipher(tfm);
-	return res;
-}
-
-/*
- * Search the current task's subscribed keyrings for a "logon" key with
- * description prefix:descriptor, and if found acquire a read lock on it and
- * return a pointer to its validated payload in *payload_ret.
- */
-static struct key *
-find_and_lock_process_key(const char *prefix,
-			  const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE],
-			  unsigned int min_keysize,
-			  const struct fscrypt_key **payload_ret)
-{
-	char *description;
-	struct key *key;
-	const struct user_key_payload *ukp;
-	const struct fscrypt_key *payload;
-
-	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
-				FS_KEY_DESCRIPTOR_SIZE, descriptor);
-	if (!description)
-		return ERR_PTR(-ENOMEM);
-
-	key = request_key(&key_type_logon, description, NULL);
-	kfree(description);
-	if (IS_ERR(key))
-		return key;
-
-	down_read(&key->sem);
-	ukp = user_key_payload_locked(key);
-
-	if (!ukp) /* was the key revoked before we acquired its semaphore? */
-		goto invalid;
-
-	payload = (const struct fscrypt_key *)ukp->data;
-
-	if (ukp->datalen != sizeof(struct fscrypt_key) ||
-	    payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) {
-		fscrypt_warn(NULL,
-			     "key with description '%s' has invalid payload",
-			     key->description);
-		goto invalid;
-	}
-
-	if (payload->size < min_keysize) {
-		fscrypt_warn(NULL,
-			     "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
-			     key->description, payload->size, min_keysize);
-		goto invalid;
-	}
-
-	*payload_ret = payload;
-	return key;
-
-invalid:
-	up_read(&key->sem);
-	key_put(key);
-	return ERR_PTR(-ENOKEY);
-}
-
 static struct fscrypt_mode available_modes[] = {
-	[FS_ENCRYPTION_MODE_AES_256_XTS] = {
+	[FSCRYPT_MODE_AES_256_XTS] = {
 		.friendly_name = "AES-256-XTS",
 		.cipher_str = "xts(aes)",
 		.keysize = 64,
 		.ivsize = 16,
 	},
-	[FS_ENCRYPTION_MODE_AES_256_CTS] = {
+	[FSCRYPT_MODE_AES_256_CTS] = {
 		.friendly_name = "AES-256-CTS-CBC",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 32,
 		.ivsize = 16,
 	},
-	[FS_ENCRYPTION_MODE_AES_128_CBC] = {
+	[FSCRYPT_MODE_AES_128_CBC] = {
 		.friendly_name = "AES-128-CBC",
 		.cipher_str = "cbc(aes)",
 		.keysize = 16,
 		.ivsize = 16,
 		.needs_essiv = true,
 	},
-	[FS_ENCRYPTION_MODE_AES_128_CTS] = {
+	[FSCRYPT_MODE_AES_128_CTS] = {
 		.friendly_name = "AES-128-CTS-CBC",
 		.cipher_str = "cts(cbc(aes))",
 		.keysize = 16,
 		.ivsize = 16,
 	},
-	[FS_ENCRYPTION_MODE_ADIANTUM] = {
+	[FSCRYPT_MODE_ADIANTUM] = {
 		.friendly_name = "Adiantum",
 		.cipher_str = "adiantum(xchacha12,aes)",
 		.keysize = 32,
@@ -163,84 +52,38 @@ static struct fscrypt_mode available_modes[] = {
 };
 
 static struct fscrypt_mode *
-select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
+select_encryption_mode(const union fscrypt_policy *policy,
+		       const struct inode *inode)
 {
-	if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
-		fscrypt_warn(inode->i_sb,
-			     "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)",
-			     inode->i_ino, ci->ci_data_mode,
-			     ci->ci_filename_mode);
-		return ERR_PTR(-EINVAL);
-	}
-
 	if (S_ISREG(inode->i_mode))
-		return &available_modes[ci->ci_data_mode];
+		return &available_modes[fscrypt_policy_contents_mode(policy)];
 
 	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
-		return &available_modes[ci->ci_filename_mode];
+		return &available_modes[fscrypt_policy_fnames_mode(policy)];
 
 	WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
 		  inode->i_ino, (inode->i_mode & S_IFMT));
 	return ERR_PTR(-EINVAL);
 }
 
-/* Find the master key, then derive the inode's actual encryption key */
-static int find_and_derive_key(const struct inode *inode,
-			       const struct fscrypt_context *ctx,
-			       u8 *derived_key, const struct fscrypt_mode *mode)
-{
-	struct key *key;
-	const struct fscrypt_key *payload;
-	int err;
-
-	key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
-					ctx->master_key_descriptor,
-					mode->keysize, &payload);
-	if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
-		key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
-						ctx->master_key_descriptor,
-						mode->keysize, &payload);
-	}
-	if (IS_ERR(key))
-		return PTR_ERR(key);
-
-	if (ctx->flags & FS_POLICY_FLAG_DIRECT_KEY) {
-		if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
-			fscrypt_warn(inode->i_sb,
-				     "direct key mode not allowed with %s",
-				     mode->friendly_name);
-			err = -EINVAL;
-		} else if (ctx->contents_encryption_mode !=
-			   ctx->filenames_encryption_mode) {
-			fscrypt_warn(inode->i_sb,
-				     "direct key mode not allowed with different contents and filenames modes");
-			err = -EINVAL;
-		} else {
-			memcpy(derived_key, payload->raw, mode->keysize);
-			err = 0;
-		}
-	} else {
-		err = derive_key_aes(payload->raw, ctx, derived_key,
-				     mode->keysize);
-	}
-	up_read(&key->sem);
-	key_put(key);
-	return err;
-}
-
-/* Allocate and key a symmetric cipher object for the given encryption mode */
-static struct crypto_skcipher *
-allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
-			   const struct inode *inode)
+/* Create a symmetric cipher object for the given encryption mode and key */
+struct crypto_skcipher *fscrypt_allocate_skcipher(struct fscrypt_mode *mode,
+						  const u8 *raw_key,
+						  const struct inode *inode)
 {
 	struct crypto_skcipher *tfm;
 	int err;
 
 	tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
 	if (IS_ERR(tfm)) {
-		fscrypt_warn(inode->i_sb,
-			     "error allocating '%s' transform for inode %lu: %ld",
-			     mode->cipher_str, inode->i_ino, PTR_ERR(tfm));
+		if (PTR_ERR(tfm) == -ENOENT) {
+			fscrypt_warn(inode,
+				     "Missing crypto API support for %s (API name: \"%s\")",
+				     mode->friendly_name, mode->cipher_str);
+			return ERR_PTR(-ENOPKG);
+		}
+		fscrypt_err(inode, "Error allocating '%s' transform: %ld",
+			    mode->cipher_str, PTR_ERR(tfm));
 		return tfm;
 	}
 	if (unlikely(!mode->logged_impl_name)) {
@@ -268,114 +111,6 @@ allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
 	return ERR_PTR(err);
 }
 
-/* Master key referenced by FS_POLICY_FLAG_DIRECT_KEY policy */
-struct fscrypt_master_key {
-	struct hlist_node mk_node;
-	refcount_t mk_refcount;
-	const struct fscrypt_mode *mk_mode;
-	struct crypto_skcipher *mk_ctfm;
-	u8 mk_descriptor[FS_KEY_DESCRIPTOR_SIZE];
-	u8 mk_raw[FS_MAX_KEY_SIZE];
-};
-
-static void free_master_key(struct fscrypt_master_key *mk)
-{
-	if (mk) {
-		crypto_free_skcipher(mk->mk_ctfm);
-		kzfree(mk);
-	}
-}
-
-static void put_master_key(struct fscrypt_master_key *mk)
-{
-	if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock))
-		return;
-	hash_del(&mk->mk_node);
-	spin_unlock(&fscrypt_master_keys_lock);
-
-	free_master_key(mk);
-}
-
-/*
- * Find/insert the given master key into the fscrypt_master_keys table.  If
- * found, it is returned with elevated refcount, and 'to_insert' is freed if
- * non-NULL.  If not found, 'to_insert' is inserted and returned if it's
- * non-NULL; otherwise NULL is returned.
- */
-static struct fscrypt_master_key *
-find_or_insert_master_key(struct fscrypt_master_key *to_insert,
-			  const u8 *raw_key, const struct fscrypt_mode *mode,
-			  const struct fscrypt_info *ci)
-{
-	unsigned long hash_key;
-	struct fscrypt_master_key *mk;
-
-	/*
-	 * Careful: to avoid potentially leaking secret key bytes via timing
-	 * information, we must key the hash table by descriptor rather than by
-	 * raw key, and use crypto_memneq() when comparing raw keys.
-	 */
-
-	BUILD_BUG_ON(sizeof(hash_key) > FS_KEY_DESCRIPTOR_SIZE);
-	memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
-
-	spin_lock(&fscrypt_master_keys_lock);
-	hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) {
-		if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor,
-			   FS_KEY_DESCRIPTOR_SIZE) != 0)
-			continue;
-		if (mode != mk->mk_mode)
-			continue;
-		if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize))
-			continue;
-		/* using existing tfm with same (descriptor, mode, raw_key) */
-		refcount_inc(&mk->mk_refcount);
-		spin_unlock(&fscrypt_master_keys_lock);
-		free_master_key(to_insert);
-		return mk;
-	}
-	if (to_insert)
-		hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key);
-	spin_unlock(&fscrypt_master_keys_lock);
-	return to_insert;
-}
-
-/* Prepare to encrypt directly using the master key in the given mode */
-static struct fscrypt_master_key *
-fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
-		       const u8 *raw_key, const struct inode *inode)
-{
-	struct fscrypt_master_key *mk;
-	int err;
-
-	/* Is there already a tfm for this key? */
-	mk = find_or_insert_master_key(NULL, raw_key, mode, ci);
-	if (mk)
-		return mk;
-
-	/* Nope, allocate one. */
-	mk = kzalloc(sizeof(*mk), GFP_NOFS);
-	if (!mk)
-		return ERR_PTR(-ENOMEM);
-	refcount_set(&mk->mk_refcount, 1);
-	mk->mk_mode = mode;
-	mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
-	if (IS_ERR(mk->mk_ctfm)) {
-		err = PTR_ERR(mk->mk_ctfm);
-		mk->mk_ctfm = NULL;
-		goto err_free_mk;
-	}
-	memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor,
-	       FS_KEY_DESCRIPTOR_SIZE);
-	memcpy(mk->mk_raw, raw_key, mode->keysize);
-
-	return find_or_insert_master_key(mk, raw_key, mode, ci);
-
-err_free_mk:
-	free_master_key(mk);
-	return ERR_PTR(err);
-}
-
 static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
 {
 	struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
@@ -386,9 +121,14 @@ static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
 
 		tfm = crypto_alloc_shash("sha256", 0, 0);
 		if (IS_ERR(tfm)) {
-			fscrypt_warn(NULL,
-				     "error allocating SHA-256 transform: %ld",
-				     PTR_ERR(tfm));
+			if (PTR_ERR(tfm) == -ENOENT) {
+				fscrypt_warn(NULL,
+					     "Missing crypto API support for SHA-256");
+				return -ENOPKG;
+			}
+			fscrypt_err(NULL,
+				    "Error allocating SHA-256 transform: %ld",
+				    PTR_ERR(tfm));
 			return PTR_ERR(tfm);
 		}
 		prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
@@ -413,6 +153,9 @@ static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
 	struct crypto_cipher *essiv_tfm;
 	u8 salt[SHA256_DIGEST_SIZE];
 
+	if (WARN_ON(ci->ci_mode->ivsize != AES_BLOCK_SIZE))
+		return -EINVAL;
+
 	essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
 	if (IS_ERR(essiv_tfm))
 		return PTR_ERR(essiv_tfm);
@@ -437,74 +180,250 @@ static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
 	return err;
 }
 
-void __exit fscrypt_essiv_cleanup(void)
+/* Given the per-file key, set up the file's crypto transform object(s) */
+int fscrypt_set_derived_key(struct fscrypt_info *ci, const u8 *derived_key)
+{
+	struct fscrypt_mode *mode = ci->ci_mode;
+	struct crypto_skcipher *ctfm;
+	int err;
+
+	ctfm = fscrypt_allocate_skcipher(mode, derived_key, ci->ci_inode);
+	if (IS_ERR(ctfm))
+		return PTR_ERR(ctfm);
+
+	ci->ci_ctfm = ctfm;
+
+	if (mode->needs_essiv) {
+		err = init_essiv_generator(ci, derived_key, mode->keysize);
+		if (err) {
+			fscrypt_warn(ci->ci_inode,
+				     "Error initializing ESSIV generator: %d",
+				     err);
+			return err;
+		}
+	}
+	return 0;
+}
+
+static int setup_per_mode_key(struct fscrypt_info *ci,
+			      struct fscrypt_master_key *mk)
 {
-	crypto_free_shash(essiv_hash_tfm);
+	struct fscrypt_mode *mode = ci->ci_mode;
+	u8 mode_num = mode - available_modes;
+	struct crypto_skcipher *tfm, *prev_tfm;
+	u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
+	int err;
+
+	if (WARN_ON(mode_num >= ARRAY_SIZE(mk->mk_mode_keys)))
+		return -EINVAL;
+
+	/* pairs with cmpxchg() below */
+	tfm = READ_ONCE(mk->mk_mode_keys[mode_num]);
+	if (likely(tfm != NULL))
+		goto done;
+
+	BUILD_BUG_ON(sizeof(mode_num) != 1);
+	err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
+				  HKDF_CONTEXT_PER_MODE_KEY,
+				  &mode_num, sizeof(mode_num),
+				  mode_key, mode->keysize);
+	if (err)
+		return err;
+	tfm = fscrypt_allocate_skcipher(mode, mode_key, ci->ci_inode);
+	memzero_explicit(mode_key, mode->keysize);
+	if (IS_ERR(tfm))
+		return PTR_ERR(tfm);
+
+	/* pairs with READ_ONCE() above */
+	prev_tfm = cmpxchg(&mk->mk_mode_keys[mode_num], NULL, tfm);
+	if (prev_tfm != NULL) {
+		crypto_free_skcipher(tfm);
+		tfm = prev_tfm;
+	}
+done:
+	ci->ci_ctfm = tfm;
+	return 0;
+}
+
+static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
+				     struct fscrypt_master_key *mk)
+{
+	u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
+	int err;
+
+	if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
+		/*
+		 * DIRECT_KEY: instead of deriving per-file keys, the per-file
+		 * nonce will be included in all the IVs.  But unlike v1
+		 * policies, for v2 policies in this case we don't encrypt with
+		 * the master key directly but rather derive a per-mode key.
+		 * This ensures that the master key is consistently used only
+		 * for HKDF, avoiding key reuse issues.
+		 */
+		if (!fscrypt_mode_supports_direct_key(ci->ci_mode)) {
+			fscrypt_warn(ci->ci_inode,
+				     "Direct key flag not allowed with %s",
+				     ci->ci_mode->friendly_name);
+			return -EINVAL;
+		}
+		return setup_per_mode_key(ci, mk);
+	}
+
+	err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
+				  HKDF_CONTEXT_PER_FILE_KEY,
+				  ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE,
+				  derived_key, ci->ci_mode->keysize);
+	if (err)
+		return err;
+
+	err = fscrypt_set_derived_key(ci, derived_key);
+	memzero_explicit(derived_key, ci->ci_mode->keysize);
+	return err;
 }
 
 /*
- * Given the encryption mode and key (normally the derived key, but for
- * FS_POLICY_FLAG_DIRECT_KEY mode it's the master key), set up the inode's
- * symmetric cipher transform object(s).
+ * Find the master key, then set up the inode's actual encryption key.
+ *
+ * If the master key is found in the filesystem-level keyring, then the
+ * corresponding 'struct key' is returned in *master_key_ret with
+ * ->mk_secret_sem read-locked.  This is needed to ensure that only one task
+ * links the fscrypt_info into ->mk_decrypted_inodes (as multiple tasks may race
+ * to create an fscrypt_info for the same inode), and to synchronize the master
+ * key being removed with a new inode starting to use it.
  */
-static int setup_crypto_transform(struct fscrypt_info *ci,
-				  struct fscrypt_mode *mode,
-				  const u8 *raw_key, const struct inode *inode)
+static int setup_file_encryption_key(struct fscrypt_info *ci,
+				     struct key **master_key_ret)
 {
-	struct fscrypt_master_key *mk;
-	struct crypto_skcipher *ctfm;
+	struct key *key;
+	struct fscrypt_master_key *mk = NULL;
+	struct fscrypt_key_specifier mk_spec;
 	int err;
 
-	if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) {
-		mk = fscrypt_get_master_key(ci, mode, raw_key, inode);
-		if (IS_ERR(mk))
-			return PTR_ERR(mk);
-		ctfm = mk->mk_ctfm;
-	} else {
-		mk = NULL;
-		ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
-		if (IS_ERR(ctfm))
-			return PTR_ERR(ctfm);
+	switch (ci->ci_policy.version) {
+	case FSCRYPT_POLICY_V1:
+		mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR;
+		memcpy(mk_spec.u.descriptor,
+		       ci->ci_policy.v1.master_key_descriptor,
+		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+		break;
+	case FSCRYPT_POLICY_V2:
+		mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
+		memcpy(mk_spec.u.identifier,
+		       ci->ci_policy.v2.master_key_identifier,
+		       FSCRYPT_KEY_IDENTIFIER_SIZE);
+		break;
+	default:
+		WARN_ON(1);
+		return -EINVAL;
 	}
-	ci->ci_master_key = mk;
-	ci->ci_ctfm = ctfm;
 
-	if (mode->needs_essiv) {
-		/* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
-		WARN_ON(mode->ivsize != AES_BLOCK_SIZE);
-		WARN_ON(ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY);
+	key = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec);
+	if (IS_ERR(key)) {
+		if (key != ERR_PTR(-ENOKEY) ||
+		    ci->ci_policy.version != FSCRYPT_POLICY_V1)
+			return PTR_ERR(key);
 
-		err = init_essiv_generator(ci, raw_key, mode->keysize);
-		if (err) {
-			fscrypt_warn(inode->i_sb,
-				     "error initializing ESSIV generator for inode %lu: %d",
-				     inode->i_ino, err);
-			return err;
-		}
+		/*
+		 * As a legacy fallback for v1 policies, search for the key in
+		 * the current task's subscribed keyrings too.  Don't move this
+		 * to before the search of ->s_master_keys, since users
+		 * shouldn't be able to override filesystem-level keys.
+		 */
+		return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+	}
+
+	mk = key->payload.data[0];
+	down_read(&mk->mk_secret_sem);
+
+	/* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
+	if (!is_master_key_secret_present(&mk->mk_secret)) {
+		err = -ENOKEY;
+		goto out_release_key;
+	}
+
+	/*
+	 * Require that the master key be at least as long as the derived key.
+	 * Otherwise, the derived key cannot possibly contain as much entropy as
+	 * that required by the encryption mode it will be used for.  For v1
+	 * policies it's also required for the KDF to work at all.
+	 */
+	if (mk->mk_secret.size < ci->ci_mode->keysize) {
+		fscrypt_warn(NULL,
+			     "key with %s %*phN is too short (got %u bytes, need %u+ bytes)",
+			     master_key_spec_type(&mk_spec),
+			     master_key_spec_len(&mk_spec), (u8 *)&mk_spec.u,
+			     mk->mk_secret.size, ci->ci_mode->keysize);
+		err = -ENOKEY;
+		goto out_release_key;
+	}
+
+	switch (ci->ci_policy.version) {
+	case FSCRYPT_POLICY_V1:
+		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
+		break;
+	case FSCRYPT_POLICY_V2:
+		err = fscrypt_setup_v2_file_key(ci, mk);
+		break;
+	default:
+		WARN_ON(1);
+		err = -EINVAL;
+		break;
 	}
+	if (err)
+		goto out_release_key;
+
+	*master_key_ret = key;
 	return 0;
+
+out_release_key:
+	up_read(&mk->mk_secret_sem);
+	key_put(key);
+	return err;
 }
 
 static void put_crypt_info(struct fscrypt_info *ci)
 {
+	struct key *key;
+
 	if (!ci)
 		return;
 
-	if (ci->ci_master_key) {
-		put_master_key(ci->ci_master_key);
-	} else {
+	if (ci->ci_direct_key) {
+		fscrypt_put_direct_key(ci->ci_direct_key);
+	} else if ((ci->ci_ctfm != NULL || ci->ci_essiv_tfm != NULL) &&
+		   !fscrypt_is_direct_key_policy(&ci->ci_policy)) {
 		crypto_free_skcipher(ci->ci_ctfm);
 		crypto_free_cipher(ci->ci_essiv_tfm);
 	}
+
+	key = ci->ci_master_key;
+	if (key) {
+		struct fscrypt_master_key *mk = key->payload.data[0];
+
+		/*
+		 * Remove this inode from the list of inodes that were unlocked
+		 * with the master key.
+		 *
+		 * In addition, if we're removing the last inode from a key that
+		 * already had its secret removed, invalidate the key so that it
+		 * gets removed from ->s_master_keys.
+		 */
+		spin_lock(&mk->mk_decrypted_inodes_lock);
+		list_del(&ci->ci_master_key_link);
+		spin_unlock(&mk->mk_decrypted_inodes_lock);
+		if (refcount_dec_and_test(&mk->mk_refcount))
+			key_invalidate(key);
+		key_put(key);
+	}
 	kmem_cache_free(fscrypt_info_cachep, ci);
 }
 
 int fscrypt_get_encryption_info(struct inode *inode)
 {
 	struct fscrypt_info *crypt_info;
-	struct fscrypt_context ctx;
+	union fscrypt_context ctx;
 	struct fscrypt_mode *mode;
-	u8 *raw_key = NULL;
+	struct key *master_key = NULL;
 	int res;
 
 	if (fscrypt_has_encryption_key(inode))
@@ -517,67 +436,92 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
 	if (res < 0) {
 		if (!fscrypt_dummy_context_enabled(inode) ||
-		    IS_ENCRYPTED(inode))
+		    IS_ENCRYPTED(inode)) {
+			fscrypt_warn(inode,
+				     "Error %d getting encryption context",
+				     res);
 			return res;
+		}
 		/* Fake up a context for an unencrypted directory */
 		memset(&ctx, 0, sizeof(ctx));
-		ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-		ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
-		ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
-		memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
-	} else if (res != sizeof(ctx)) {
-		return -EINVAL;
+		ctx.version = FSCRYPT_CONTEXT_V1;
+		ctx.v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS;
+		ctx.v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS;
+		memset(ctx.v1.master_key_descriptor, 0x42,
+		       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+		res = sizeof(ctx.v1);
 	}
 
-	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
-		return -EINVAL;
-
-	if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
-		return -EINVAL;
-
 	crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
 	if (!crypt_info)
 		return -ENOMEM;
 
-	crypt_info->ci_flags = ctx.flags;
-	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
-	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
-	memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
-	       FS_KEY_DESCRIPTOR_SIZE);
-	memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	crypt_info->ci_inode = inode;
 
-	mode = select_encryption_mode(crypt_info, inode);
-	if (IS_ERR(mode)) {
-		res = PTR_ERR(mode);
+	res = fscrypt_policy_from_context(&crypt_info->ci_policy, &ctx, res);
+	if (res) {
+		fscrypt_warn(inode,
+			     "Unrecognized or corrupt encryption context");
 		goto out;
 	}
-	WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
-	crypt_info->ci_mode = mode;
 
-	/*
-	 * This cannot be a stack buffer because it may be passed to the
-	 * scatterlist crypto API as part of key derivation.
-	 */
-	res = -ENOMEM;
-	raw_key = kmalloc(mode->keysize, GFP_NOFS);
-	if (!raw_key)
+	switch (ctx.version) {
+	case FSCRYPT_CONTEXT_V1:
+		memcpy(crypt_info->ci_nonce, ctx.v1.nonce,
+		       FS_KEY_DERIVATION_NONCE_SIZE);
+		break;
+	case FSCRYPT_CONTEXT_V2:
+		memcpy(crypt_info->ci_nonce, ctx.v2.nonce,
+		       FS_KEY_DERIVATION_NONCE_SIZE);
+		break;
+	default:
+		WARN_ON(1);
+		res = -EINVAL;
 		goto out;
+	}
 
-	res = find_and_derive_key(inode, &ctx, raw_key, mode);
-	if (res)
+	if (!fscrypt_supported_policy(&crypt_info->ci_policy, inode)) {
+		res = -EINVAL;
 		goto out;
+	}
 
-	res = setup_crypto_transform(crypt_info, mode, raw_key, inode);
+	mode = select_encryption_mode(&crypt_info->ci_policy, inode);
+	if (IS_ERR(mode)) {
+		res = PTR_ERR(mode);
+		goto out;
+	}
+	WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
+	crypt_info->ci_mode = mode;
+
+	res = setup_file_encryption_key(crypt_info, &master_key);
 	if (res)
 		goto out;
 
-	if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL)
+	if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {
+		if (master_key) {
+			struct fscrypt_master_key *mk =
+				master_key->payload.data[0];
+
+			refcount_inc(&mk->mk_refcount);
+			crypt_info->ci_master_key = key_get(master_key);
+			spin_lock(&mk->mk_decrypted_inodes_lock);
+			list_add(&crypt_info->ci_master_key_link,
+				 &mk->mk_decrypted_inodes);
+			spin_unlock(&mk->mk_decrypted_inodes_lock);
+		}
 		crypt_info = NULL;
+	}
+	res = 0;
 out:
+	if (master_key) {
+		struct fscrypt_master_key *mk = master_key->payload.data[0];
+
+		up_read(&mk->mk_secret_sem);
+		key_put(master_key);
+	}
 	if (res == -ENOKEY)
 		res = 0;
 	put_crypt_info(crypt_info);
-	kzfree(raw_key);
 	return res;
 }
 EXPORT_SYMBOL(fscrypt_get_encryption_info);
@@ -609,3 +553,39 @@ void fscrypt_free_inode(struct inode *inode)
 	}
 }
 EXPORT_SYMBOL(fscrypt_free_inode);
+
+/**
+ * fscrypt_drop_inode - check whether the inode's master key has been removed
+ *
+ * Filesystems supporting fscrypt must call this from their ->drop_inode()
+ * method so that encrypted inodes are evicted as soon as they're no longer in
+ * use and their master key has been removed.
+ *
+ * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0
+ */
+int fscrypt_drop_inode(struct inode *inode)
+{
+	const struct fscrypt_info *ci = READ_ONCE(inode->i_crypt_info);
+	const struct fscrypt_master_key *mk;
+
+	/*
+	 * If ci is NULL, then the inode doesn't have an encryption key set up
+	 * so it's irrelevant.  If ci_master_key is NULL, then the master key
+	 * was provided via the legacy mechanism of the process-subscribed
+	 * keyrings, so we don't know whether it's been removed or not.
+	 */
+	if (!ci || !ci->ci_master_key)
+		return 0;
+	mk = ci->ci_master_key->payload.data[0];
+
+	/*
+	 * Note: since we aren't holding ->mk_secret_sem, the result here can
+	 * immediately become outdated.  But there's no correctness problem with
+	 * unnecessarily evicting.  Nor is there a correctness problem with not
+	 * evicting while iput() is racing with the key being removed, since
+	 * then the thread removing the key will either evict the inode itself
+	 * or will correctly detect that it wasn't evicted due to the race.
+	 */
+	return !is_master_key_secret_present(&mk->mk_secret);
+}
+EXPORT_SYMBOL_GPL(fscrypt_drop_inode);

fs/crypto/keysetup_v1.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Key setup for v1 encryption policies
+ *
+ * Copyright 2015, 2019 Google LLC
+ */
+
+/*
+ * This file implements compatibility functions for the original encryption
+ * policy version ("v1"), including:
+ *
+ * - Deriving per-file keys using the AES-128-ECB based KDF
+ *   (rather than the new method of using HKDF-SHA512)
+ *
+ * - Retrieving fscrypt master keys from process-subscribed keyrings
+ *   (rather than the new method of using a filesystem-level keyring)
+ *
+ * - Handling policies with the DIRECT_KEY flag set using a master key table
+ *   (rather than the new method of implementing DIRECT_KEY with per-mode keys
+ *    managed alongside the master keys in the filesystem-level keyring)
+ */
+
+#include <crypto/algapi.h>
+#include <crypto/skcipher.h>
+#include <keys/user-type.h>
+#include <linux/hashtable.h>
+#include <linux/scatterlist.h>
+
+#include "fscrypt_private.h"
+
+/* Table of keys referenced by DIRECT_KEY policies */
+static DEFINE_HASHTABLE(fscrypt_direct_keys, 6); /* 6 bits = 64 buckets */
+static DEFINE_SPINLOCK(fscrypt_direct_keys_lock);
+
+/*
+ * v1 key derivation function.  This generates the derived key by encrypting the
+ * master key with AES-128-ECB using the nonce as the AES key.  This provides a
+ * unique derived key with sufficient entropy for each inode.  However, it's
+ * nonstandard, non-extensible, doesn't evenly distribute the entropy from the
+ * master key, and is trivially reversible: an attacker who compromises a
+ * derived key can "decrypt" it to get back to the master key, then derive any
+ * other key.  For all new code, use HKDF instead.
+ *
+ * The master key must be at least as long as the derived key.  If the master
+ * key is longer, then only the first 'derived_keysize' bytes are used.
+ */
+static int derive_key_aes(const u8 *master_key,
+			  const u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE],
+			  u8 *derived_key, unsigned int derived_keysize)
+{
+	int res = 0;
+	struct skcipher_request *req = NULL;
+	DECLARE_CRYPTO_WAIT(wait);
+	struct scatterlist src_sg, dst_sg;
+	struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
+
+	if (IS_ERR(tfm)) {
+		res = PTR_ERR(tfm);
+		tfm = NULL;
+		goto out;
+	}
+	crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
+	req = skcipher_request_alloc(tfm, GFP_NOFS);
+	if (!req) {
+		res = -ENOMEM;
+		goto out;
+	}
+	skcipher_request_set_callback(req,
+			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+			crypto_req_done, &wait);
+	res = crypto_skcipher_setkey(tfm, nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	if (res < 0)
+		goto out;
+
+	sg_init_one(&src_sg, master_key, derived_keysize);
+	sg_init_one(&dst_sg, derived_key, derived_keysize);
+	skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
+				   NULL);
+	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+out:
+	skcipher_request_free(req);
+	crypto_free_skcipher(tfm);
+	return res;
+}
+
+/*
+ * Search the current task's subscribed keyrings for a "logon" key with
+ * description prefix:descriptor, and if found acquire a read lock on it and
+ * return a pointer to its validated payload in *payload_ret.
+ */
+static struct key *
+find_and_lock_process_key(const char *prefix,
+			  const u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE],
+			  unsigned int min_keysize,
+			  const struct fscrypt_key **payload_ret)
+{
+	char *description;
+	struct key *key;
+	const struct user_key_payload *ukp;
+	const struct fscrypt_key *payload;
+
+	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
+				FSCRYPT_KEY_DESCRIPTOR_SIZE, descriptor);
+	if (!description)
+		return ERR_PTR(-ENOMEM);
+
+	key = request_key(&key_type_logon, description, NULL);
+	kfree(description);
+	if (IS_ERR(key))
+		return key;
+
+	down_read(&key->sem);
+	ukp = user_key_payload_locked(key);
+
+	if (!ukp) /* was the key revoked before we acquired its semaphore? */
+		goto invalid;
+
+	payload = (const struct fscrypt_key *)ukp->data;
+
+	if (ukp->datalen != sizeof(struct fscrypt_key) ||
+	    payload->size < 1 || payload->size > FSCRYPT_MAX_KEY_SIZE) {
+		fscrypt_warn(NULL,
+			     "key with description '%s' has invalid payload",
+			     key->description);
+		goto invalid;
+	}
+
+	if (payload->size < min_keysize) {
+		fscrypt_warn(NULL,
+			     "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
+			     key->description, payload->size, min_keysize);
+		goto invalid;
+	}
+
+	*payload_ret = payload;
+	return key;
+
+invalid:
+	up_read(&key->sem);
+	key_put(key);
+	return ERR_PTR(-ENOKEY);
+}
+
+/* Master key referenced by DIRECT_KEY policy */
+struct fscrypt_direct_key {
+	struct hlist_node		dk_node;
+	refcount_t			dk_refcount;
+	const struct fscrypt_mode	*dk_mode;
+	struct crypto_skcipher		*dk_ctfm;
+	u8				dk_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+	u8				dk_raw[FSCRYPT_MAX_KEY_SIZE];
+};
+
+static void free_direct_key(struct fscrypt_direct_key *dk)
+{
+	if (dk) {
+		crypto_free_skcipher(dk->dk_ctfm);
+		kzfree(dk);
+	}
+}
+
+void fscrypt_put_direct_key(struct fscrypt_direct_key *dk)
+{
+	if (!refcount_dec_and_lock(&dk->dk_refcount, &fscrypt_direct_keys_lock))
+		return;
+	hash_del(&dk->dk_node);
+	spin_unlock(&fscrypt_direct_keys_lock);
+
+	free_direct_key(dk);
+}
+
+/*
+ * Find/insert the given key into the fscrypt_direct_keys table.  If found, it
+ * is returned with elevated refcount, and 'to_insert' is freed if non-NULL.  If
+ * not found, 'to_insert' is inserted and returned if it's non-NULL; otherwise
+ * NULL is returned.
+ */
+static struct fscrypt_direct_key *
+find_or_insert_direct_key(struct fscrypt_direct_key *to_insert,
+			  const u8 *raw_key, const struct fscrypt_info *ci)
+{
+	unsigned long hash_key;
+	struct fscrypt_direct_key *dk;
+
+	/*
+	 * Careful: to avoid potentially leaking secret key bytes via timing
+	 * information, we must key the hash table by descriptor rather than by
+	 * raw key, and use crypto_memneq() when comparing raw keys.
+	 */
+
+	BUILD_BUG_ON(sizeof(hash_key) > FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	memcpy(&hash_key, ci->ci_policy.v1.master_key_descriptor,
+	       sizeof(hash_key));
+
+	spin_lock(&fscrypt_direct_keys_lock);
+	hash_for_each_possible(fscrypt_direct_keys, dk, dk_node, hash_key) {
+		if (memcmp(ci->ci_policy.v1.master_key_descriptor,
+			   dk->dk_descriptor, FSCRYPT_KEY_DESCRIPTOR_SIZE) != 0)
+			continue;
+		if (ci->ci_mode != dk->dk_mode)
+			continue;
+		if (crypto_memneq(raw_key, dk->dk_raw, ci->ci_mode->keysize))
+			continue;
+		/* using existing tfm with same (descriptor, mode, raw_key) */
+		refcount_inc(&dk->dk_refcount);
+		spin_unlock(&fscrypt_direct_keys_lock);
+		free_direct_key(to_insert);
+		return dk;
+	}
+	if (to_insert)
+		hash_add(fscrypt_direct_keys, &to_insert->dk_node, hash_key);
+	spin_unlock(&fscrypt_direct_keys_lock);
+	return to_insert;
+}
+
+/* Prepare to encrypt directly using the master key in the given mode */
+static struct fscrypt_direct_key *
+fscrypt_get_direct_key(const struct fscrypt_info *ci, const u8 *raw_key)
+{
+	struct fscrypt_direct_key *dk;
+	int err;
+
+	/* Is there already a tfm for this key? */
+	dk = find_or_insert_direct_key(NULL, raw_key, ci);
+	if (dk)
+		return dk;
+
+	/* Nope, allocate one. */
+	dk = kzalloc(sizeof(*dk), GFP_NOFS);
+	if (!dk)
+		return ERR_PTR(-ENOMEM);
+	refcount_set(&dk->dk_refcount, 1);
+	dk->dk_mode = ci->ci_mode;
+	dk->dk_ctfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key,
+						ci->ci_inode);
+	if (IS_ERR(dk->dk_ctfm)) {
+		err = PTR_ERR(dk->dk_ctfm);
+		dk->dk_ctfm = NULL;
+		goto err_free_dk;
+	}
+	memcpy(dk->dk_descriptor, ci->ci_policy.v1.master_key_descriptor,
+	       FSCRYPT_KEY_DESCRIPTOR_SIZE);
+	memcpy(dk->dk_raw, raw_key, ci->ci_mode->keysize);
+
+	return find_or_insert_direct_key(dk, raw_key, ci);
+
+err_free_dk:
+	free_direct_key(dk);
+	return ERR_PTR(err);
+}
+
+/* v1 policy, DIRECT_KEY: use the master key directly */
+static int setup_v1_file_key_direct(struct fscrypt_info *ci,
+				    const u8 *raw_master_key)
+{
+	const struct fscrypt_mode *mode = ci->ci_mode;
+	struct fscrypt_direct_key *dk;
+
+	if (!fscrypt_mode_supports_direct_key(mode)) {
+		fscrypt_warn(ci->ci_inode,
+			     "Direct key mode not allowed with %s",
+			     mode->friendly_name);
+		return -EINVAL;
+	}
+
+	if (ci->ci_policy.v1.contents_encryption_mode !=
+	    ci->ci_policy.v1.filenames_encryption_mode) {
+		fscrypt_warn(ci->ci_inode,
+			     "Direct key mode not allowed with different contents and filenames modes");
+		return -EINVAL;
+	}
+
+	/* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
+	if (WARN_ON(mode->needs_essiv))
+		return -EINVAL;
+
+	dk = fscrypt_get_direct_key(ci, raw_master_key);
+	if (IS_ERR(dk))
+		return PTR_ERR(dk);
+	ci->ci_direct_key = dk;
+	ci->ci_ctfm = dk->dk_ctfm;
+	return 0;
+}
+
+/* v1 policy, !DIRECT_KEY: derive the file's encryption key */
+static int setup_v1_file_key_derived(struct fscrypt_info *ci,
+				     const u8 *raw_master_key)
+{
+	u8 *derived_key;
+	int err;
+
+	/*
+	 * This cannot be a stack buffer because it will be passed to the
+	 * scatterlist crypto API during derive_key_aes().
+	 */
+	derived_key = kmalloc(ci->ci_mode->keysize, GFP_NOFS);
+	if (!derived_key)
+		return -ENOMEM;
+
+	err = derive_key_aes(raw_master_key, ci->ci_nonce,
+			     derived_key, ci->ci_mode->keysize);
+	if (err)
+		goto out;
+
+	err = fscrypt_set_derived_key(ci, derived_key);
+out:
+	kzfree(derived_key);
+	return err;
+}
+
+int fscrypt_setup_v1_file_key(struct fscrypt_info *ci, const u8 *raw_master_key)
+{
+	if (ci->ci_policy.v1.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY)
+		return setup_v1_file_key_direct(ci, raw_master_key);
+	else
+		return setup_v1_file_key_derived(ci, raw_master_key);
+}
+
+int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_info *ci)
+{
+	struct key *key;
+	const struct fscrypt_key *payload;
+	int err;
+
+	key = find_and_lock_process_key(FSCRYPT_KEY_DESC_PREFIX,
+					ci->ci_policy.v1.master_key_descriptor,
+					ci->ci_mode->keysize, &payload);
+	if (key == ERR_PTR(-ENOKEY) && ci->ci_inode->i_sb->s_cop->key_prefix) {
+		key = find_and_lock_process_key(ci->ci_inode->i_sb->s_cop->key_prefix,
+						ci->ci_policy.v1.master_key_descriptor,
+						ci->ci_mode->keysize, &payload);
+	}
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+
+	err = fscrypt_setup_v1_file_key(ci, payload->raw);
+	up_read(&key->sem);
+	key_put(key);
+	return err;
+}

fs/crypto/policy.c

@@ -5,8 +5,9 @@
  * Copyright (C) 2015, Google, Inc.
  * Copyright (C) 2015, Motorola Mobility.
  *
- * Written by Michael Halcrow, 2015.
+ * Originally written by Michael Halcrow, 2015.
  * Modified by Jaegeuk Kim, 2015.
+ * Modified by Eric Biggers, 2019 for v2 policy support.
  */
 
 #include <linux/random.h>
@@ -14,70 +15,303 @@
 #include <linux/mount.h>
 #include "fscrypt_private.h"
 
-/*
- * check whether an encryption policy is consistent with an encryption context
+/**
+ * fscrypt_policies_equal - check whether two encryption policies are the same
+ *
+ * Return: %true if equal, else %false
+ */
+bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
+			    const union fscrypt_policy *policy2)
+{
+	if (policy1->version != policy2->version)
+		return false;
+
+	return !memcmp(policy1, policy2, fscrypt_policy_size(policy1));
+}
+
+/**
+ * fscrypt_supported_policy - check whether an encryption policy is supported
+ *
+ * Given an encryption policy, check whether all its encryption modes and other
+ * settings are supported by this kernel.  (But we don't currently don't check
+ * for crypto API support here, so attempting to use an algorithm not configured
+ * into the crypto API will still fail later.)
+ *
+ * Return: %true if supported, else %false
+ */
+bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
+			      const struct inode *inode)
+{
+	switch (policy_u->version) {
+	case FSCRYPT_POLICY_V1: {
+		const struct fscrypt_policy_v1 *policy = &policy_u->v1;
+
+		if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
+					     policy->filenames_encryption_mode)) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption modes (contents %d, filenames %d)",
+				     policy->contents_encryption_mode,
+				     policy->filenames_encryption_mode);
+			return false;
+		}
+
+		if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption flags (0x%02x)",
+				     policy->flags);
+			return false;
+		}
+
+		return true;
+	}
+	case FSCRYPT_POLICY_V2: {
+		const struct fscrypt_policy_v2 *policy = &policy_u->v2;
+
+		if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
+					     policy->filenames_encryption_mode)) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption modes (contents %d, filenames %d)",
+				     policy->contents_encryption_mode,
+				     policy->filenames_encryption_mode);
+			return false;
+		}
+
+		if (policy->flags & ~FSCRYPT_POLICY_FLAGS_VALID) {
+			fscrypt_warn(inode,
+				     "Unsupported encryption flags (0x%02x)",
+				     policy->flags);
+			return false;
+		}
+
+		if (memchr_inv(policy->__reserved, 0,
+			       sizeof(policy->__reserved))) {
+			fscrypt_warn(inode,
+				     "Reserved bits set in encryption policy");
+			return false;
+		}
+
+		return true;
+	}
+	}
+	return false;
+}
+
+/**
+ * fscrypt_new_context_from_policy - create a new fscrypt_context from a policy
+ *
+ * Create an fscrypt_context for an inode that is being assigned the given
+ * encryption policy.  A new nonce is randomly generated.
+ *
+ * Return: the size of the new context in bytes.
  */
-static bool is_encryption_context_consistent_with_policy(
-				const struct fscrypt_context *ctx,
-				const struct fscrypt_policy *policy)
+static int fscrypt_new_context_from_policy(union fscrypt_context *ctx_u,
+					   const union fscrypt_policy *policy_u)
 {
-	return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor,
-		      FS_KEY_DESCRIPTOR_SIZE) == 0 &&
-		(ctx->flags == policy->flags) &&
-		(ctx->contents_encryption_mode ==
-		 policy->contents_encryption_mode) &&
-		(ctx->filenames_encryption_mode ==
-		 policy->filenames_encryption_mode);
+	memset(ctx_u, 0, sizeof(*ctx_u));
+
+	switch (policy_u->version) {
+	case FSCRYPT_POLICY_V1: {
+		const struct fscrypt_policy_v1 *policy = &policy_u->v1;
+		struct fscrypt_context_v1 *ctx = &ctx_u->v1;
+
+		ctx->version = FSCRYPT_CONTEXT_V1;
+		ctx->contents_encryption_mode =
+			policy->contents_encryption_mode;
+		ctx->filenames_encryption_mode =
+			policy->filenames_encryption_mode;
+		ctx->flags = policy->flags;
+		memcpy(ctx->master_key_descriptor,
+		       policy->master_key_descriptor,
+		       sizeof(ctx->master_key_descriptor));
+		get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
+		return sizeof(*ctx);
+	}
+	case FSCRYPT_POLICY_V2: {
+		const struct fscrypt_policy_v2 *policy = &policy_u->v2;
+		struct fscrypt_context_v2 *ctx = &ctx_u->v2;
+
+		ctx->version = FSCRYPT_CONTEXT_V2;
+		ctx->contents_encryption_mode =
+			policy->contents_encryption_mode;
+		ctx->filenames_encryption_mode =
+			policy->filenames_encryption_mode;
+		ctx->flags = policy->flags;
+		memcpy(ctx->master_key_identifier,
+		       policy->master_key_identifier,
+		       sizeof(ctx->master_key_identifier));
+		get_random_bytes(ctx->nonce, sizeof(ctx->nonce));
+		return sizeof(*ctx);
+	}
+	}
+	BUG();
 }
 
-static int create_encryption_context_from_policy(struct inode *inode,
-				const struct fscrypt_policy *policy)
+/**
+ * fscrypt_policy_from_context - convert an fscrypt_context to an fscrypt_policy
+ *
+ * Given an fscrypt_context, build the corresponding fscrypt_policy.
+ *
+ * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized
+ * version number or size.
+ *
+ * This does *not* validate the settings within the policy itself, e.g. the
+ * modes, flags, and reserved bits.  Use fscrypt_supported_policy() for that.
+ */
+int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
+				const union fscrypt_context *ctx_u,
+				int ctx_size)
 {
-	struct fscrypt_context ctx;
+	memset(policy_u, 0, sizeof(*policy_u));
+
+	if (ctx_size <= 0 || ctx_size != fscrypt_context_size(ctx_u))
+		return -EINVAL;
+
+	switch (ctx_u->version) {
+	case FSCRYPT_CONTEXT_V1: {
+		const struct fscrypt_context_v1 *ctx = &ctx_u->v1;
+		struct fscrypt_policy_v1 *policy = &policy_u->v1;
+
+		policy->version = FSCRYPT_POLICY_V1;
+		policy->contents_encryption_mode =
+			ctx->contents_encryption_mode;
+		policy->filenames_encryption_mode =
+			ctx->filenames_encryption_mode;
+		policy->flags = ctx->flags;
+		memcpy(policy->master_key_descriptor,
+		       ctx->master_key_descriptor,
+		       sizeof(policy->master_key_descriptor));
+		return 0;
+	}
+	case FSCRYPT_CONTEXT_V2: {
+		const struct fscrypt_context_v2 *ctx = &ctx_u->v2;
+		struct fscrypt_policy_v2 *policy = &policy_u->v2;
+
+		policy->version = FSCRYPT_POLICY_V2;
+		policy->contents_encryption_mode =
+			ctx->contents_encryption_mode;
+		policy->filenames_encryption_mode =
+			ctx->filenames_encryption_mode;
+		policy->flags = ctx->flags;
+		memcpy(policy->__reserved, ctx->__reserved,
+		       sizeof(policy->__reserved));
+		memcpy(policy->master_key_identifier,
+		       ctx->master_key_identifier,
+		       sizeof(policy->master_key_identifier));
+		return 0;
+	}
+	}
+	/* unreachable */
+	return -EINVAL;
+}
+
+/* Retrieve an inode's encryption policy */
+static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy)
+{
+	const struct fscrypt_info *ci;
+	union fscrypt_context ctx;
+	int ret;
+
+	ci = READ_ONCE(inode->i_crypt_info);
+	if (ci) {
+		/* key available, use the cached policy */
+		*policy = ci->ci_policy;
+		return 0;
+	}
+
+	if (!IS_ENCRYPTED(inode))
+		return -ENODATA;
 
-	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
-					FS_KEY_DESCRIPTOR_SIZE);
+	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+	if (ret < 0)
+		return (ret == -ERANGE) ? -EINVAL : ret;
 
-	if (!fscrypt_valid_enc_modes(policy->contents_encryption_mode,
-				     policy->filenames_encryption_mode))
+	return fscrypt_policy_from_context(policy, &ctx, ret);
+}
+
+static int set_encryption_policy(struct inode *inode,
+				 const union fscrypt_policy *policy)
+{
+	union fscrypt_context ctx;
+	int ctxsize;
+	int err;
+
+	if (!fscrypt_supported_policy(policy, inode))
 		return -EINVAL;
 
-	if (policy->flags & ~FS_POLICY_FLAGS_VALID)
+	switch (policy->version) {
+	case FSCRYPT_POLICY_V1:
+		/*
+		 * The original encryption policy version provided no way of
+		 * verifying that the correct master key was supplied, which was
+		 * insecure in scenarios where multiple users have access to the
+		 * same encrypted files (even just read-only access).  The new
+		 * encryption policy version fixes this and also implies use of
+		 * an improved key derivation function and allows non-root users
+		 * to securely remove keys.  So as long as compatibility with
+		 * old kernels isn't required, it is recommended to use the new
+		 * policy version for all new encrypted directories.
+		 */
+		pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n",
+			     current->comm, current->pid);
+		break;
+	case FSCRYPT_POLICY_V2:
+		err = fscrypt_verify_key_added(inode->i_sb,
+					       policy->v2.master_key_identifier);
+		if (err)
+			return err;
+		break;
+	default:
+		WARN_ON(1);
 		return -EINVAL;
+	}
 
-	ctx.contents_encryption_mode = policy->contents_encryption_mode;
-	ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
-	ctx.flags = policy->flags;
-	BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE);
-	get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	ctxsize = fscrypt_new_context_from_policy(&ctx, policy);
 
-	return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
+	return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL);
 }
 
 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 {
-	struct fscrypt_policy policy;
+	union fscrypt_policy policy;
+	union fscrypt_policy existing_policy;
 	struct inode *inode = file_inode(filp);
+	u8 version;
+	int size;
 	int ret;
-	struct fscrypt_context ctx;
 
-	if (copy_from_user(&policy, arg, sizeof(policy)))
+	if (get_user(policy.version, (const u8 __user *)arg))
 		return -EFAULT;
 
+	size = fscrypt_policy_size(&policy);
+	if (size <= 0)
+		return -EINVAL;
+
+	/*
+	 * We should just copy the remaining 'size - 1' bytes here, but a
+	 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to
+	 * think that size can be 0 here (despite the check above!) *and* that
+	 * it's a compile-time constant.  Thus it would think copy_from_user()
+	 * is passed compile-time constant ULONG_MAX, causing the compile-time
+	 * buffer overflow check to fail, breaking the build. This only occurred
+	 * when building an i386 kernel with -Os and branch profiling enabled.
+	 *
+	 * Work around it by just copying the first byte again...
+	 */
+	version = policy.version;
+	if (copy_from_user(&policy, arg, size))
+		return -EFAULT;
+	policy.version = version;
+
 	if (!inode_owner_or_capable(inode))
 		return -EACCES;
 
-	if (policy.version != 0)
-		return -EINVAL;
-
 	ret = mnt_want_write_file(filp);
 	if (ret)
 		return ret;
 
 	inode_lock(inode);
 
-	ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
+	ret = fscrypt_get_policy(inode, &existing_policy);
 	if (ret == -ENODATA) {
 		if (!S_ISDIR(inode->i_mode))
 			ret = -ENOTDIR;
@@ -86,14 +320,10 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 		else if (!inode->i_sb->s_cop->empty_dir(inode))
 			ret = -ENOTEMPTY;
 		else
-			ret = create_encryption_context_from_policy(inode,
-								    &policy);
-	} else if (ret == sizeof(ctx) &&
-		   is_encryption_context_consistent_with_policy(&ctx,
-								&policy)) {
-		/* The file already uses the same encryption policy. */
-		ret = 0;
-	} else if (ret >= 0 || ret == -ERANGE) {
+			ret = set_encryption_policy(inode, &policy);
+	} else if (ret == -EINVAL ||
+		   (ret == 0 && !fscrypt_policies_equal(&policy,
+							&existing_policy))) {
 		/* The file already uses a different encryption policy. */
 		ret = -EEXIST;
 	}
@@ -105,37 +335,57 @@ int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
 }
 EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
 
+/* Original ioctl version; can only get the original policy version */
 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 {
-	struct inode *inode = file_inode(filp);
-	struct fscrypt_context ctx;
-	struct fscrypt_policy policy;
-	int res;
+	union fscrypt_policy policy;
+	int err;
 
-	if (!IS_ENCRYPTED(inode))
-		return -ENODATA;
+	err = fscrypt_get_policy(file_inode(filp), &policy);
+	if (err)
+		return err;
 
-	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
-	if (res < 0 && res != -ERANGE)
-		return res;
-	if (res != sizeof(ctx))
-		return -EINVAL;
-	if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
+	if (policy.version != FSCRYPT_POLICY_V1)
 		return -EINVAL;
 
-	policy.version = 0;
-	policy.contents_encryption_mode = ctx.contents_encryption_mode;
-	policy.filenames_encryption_mode = ctx.filenames_encryption_mode;
-	policy.flags = ctx.flags;
-	memcpy(policy.master_key_descriptor, ctx.master_key_descriptor,
-				FS_KEY_DESCRIPTOR_SIZE);
-
-	if (copy_to_user(arg, &policy, sizeof(policy)))
+	if (copy_to_user(arg, &policy, sizeof(policy.v1)))
 		return -EFAULT;
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
 
+/* Extended ioctl version; can get policies of any version */
+int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg)
+{
+	struct fscrypt_get_policy_ex_arg arg;
+	union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy;
+	size_t policy_size;
+	int err;
+
+	/* arg is policy_size, then policy */
+	BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0);
+	BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) !=
+		     offsetof(typeof(arg), policy));
+	BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy));
+
+	err = fscrypt_get_policy(file_inode(filp), policy);
+	if (err)
+		return err;
+	policy_size = fscrypt_policy_size(policy);
+
+	if (copy_from_user(&arg, uarg, sizeof(arg.policy_size)))
+		return -EFAULT;
+
+	if (policy_size > arg.policy_size)
+		return -EOVERFLOW;
+	arg.policy_size = policy_size;
+
+	if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size))
+		return -EFAULT;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex);
+
 /**
  * fscrypt_has_permitted_context() - is a file's encryption policy permitted
  *				     within its directory?
@@ -157,10 +407,8 @@ EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
  */
 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 {
-	const struct fscrypt_operations *cops = parent->i_sb->s_cop;
-	const struct fscrypt_info *parent_ci, *child_ci;
-	struct fscrypt_context parent_ctx, child_ctx;
-	int res;
+	union fscrypt_policy parent_policy, child_policy;
+	int err;
 
 	/* No restrictions on file types which are never encrypted */
 	if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
@@ -190,41 +438,22 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 	 * In any case, if an unexpected error occurs, fall back to "forbidden".
 	 */
 
-	res = fscrypt_get_encryption_info(parent);
-	if (res)
+	err = fscrypt_get_encryption_info(parent);
+	if (err)
 		return 0;
-	res = fscrypt_get_encryption_info(child);
-	if (res)
+	err = fscrypt_get_encryption_info(child);
+	if (err)
 		return 0;
-	parent_ci = READ_ONCE(parent->i_crypt_info);
-	child_ci = READ_ONCE(child->i_crypt_info);
-
-	if (parent_ci && child_ci) {
-		return memcmp(parent_ci->ci_master_key_descriptor,
-			      child_ci->ci_master_key_descriptor,
-			      FS_KEY_DESCRIPTOR_SIZE) == 0 &&
-			(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
-			(parent_ci->ci_filename_mode ==
-			 child_ci->ci_filename_mode) &&
-			(parent_ci->ci_flags == child_ci->ci_flags);
-	}
 
-	res = cops->get_context(parent, &parent_ctx, sizeof(parent_ctx));
-	if (res != sizeof(parent_ctx))
+	err = fscrypt_get_policy(parent, &parent_policy);
+	if (err)
 		return 0;
 
-	res = cops->get_context(child, &child_ctx, sizeof(child_ctx));
-	if (res != sizeof(child_ctx))
+	err = fscrypt_get_policy(child, &child_policy);
+	if (err)
 		return 0;
 
-	return memcmp(parent_ctx.master_key_descriptor,
-		      child_ctx.master_key_descriptor,
-		      FS_KEY_DESCRIPTOR_SIZE) == 0 &&
-		(parent_ctx.contents_encryption_mode ==
-		 child_ctx.contents_encryption_mode) &&
-		(parent_ctx.filenames_encryption_mode ==
-		 child_ctx.filenames_encryption_mode) &&
-		(parent_ctx.flags == child_ctx.flags);
+	return fscrypt_policies_equal(&parent_policy, &child_policy);
 }
 EXPORT_SYMBOL(fscrypt_has_permitted_context);
 
@@ -240,7 +469,8 @@ EXPORT_SYMBOL(fscrypt_has_permitted_context);
 int fscrypt_inherit_context(struct inode *parent, struct inode *child,
 						void *fs_data, bool preload)
 {
-	struct fscrypt_context ctx;
+	union fscrypt_context ctx;
+	int ctxsize;
 	struct fscrypt_info *ci;
 	int res;
 
@@ -252,16 +482,10 @@ int fscrypt_inherit_context(struct inode *parent, struct inode *child,
 	if (ci == NULL)
 		return -ENOKEY;
 
-	ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
-	ctx.contents_encryption_mode = ci->ci_data_mode;
-	ctx.filenames_encryption_mode = ci->ci_filename_mode;
-	ctx.flags = ci->ci_flags;
-	memcpy(ctx.master_key_descriptor, ci->ci_master_key_descriptor,
-	       FS_KEY_DESCRIPTOR_SIZE);
-	get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
+	ctxsize = fscrypt_new_context_from_policy(&ctx, &ci->ci_policy);
+
 	BUILD_BUG_ON(sizeof(ctx) != FSCRYPT_SET_CONTEXT_MAX_SIZE);
-	res = parent->i_sb->s_cop->set_context(child, &ctx,
-						sizeof(ctx), fs_data);
+	res = parent->i_sb->s_cop->set_context(child, &ctx, ctxsize, fs_data);
 	if (res)
 		return res;
 	return preload ? fscrypt_get_encryption_info(child): 0;

fs/ext4/ioctl.c

@@ -1113,8 +1113,35 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 #endif
 	}
 	case EXT4_IOC_GET_ENCRYPTION_POLICY:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
 		return fscrypt_ioctl_get_policy(filp, (void __user *)arg);
 
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg);
+
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_add_key(filp, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_remove_key(filp, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_remove_key_all_users(filp,
+							  (void __user *)arg);
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		if (!ext4_has_feature_encrypt(sb))
+			return -EOPNOTSUPP;
+		return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
+
 	case EXT4_IOC_FSGETXATTR:
 	{
 		struct fsxattr fa;
@@ -1231,6 +1258,11 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case EXT4_IOC_SET_ENCRYPTION_POLICY:
 	case EXT4_IOC_GET_ENCRYPTION_PWSALT:
 	case EXT4_IOC_GET_ENCRYPTION_POLICY:
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
 	case EXT4_IOC_SHUTDOWN:
 	case FS_IOC_GETFSMAP:
 		break;

fs/ext4/super.c

@@ -1107,6 +1107,9 @@ static int ext4_drop_inode(struct inode *inode)
 {
 	int drop = generic_drop_inode(inode);
 
+	if (!drop)
+		drop = fscrypt_drop_inode(inode);
+
 	trace_ext4_drop_inode(inode, drop);
 	return drop;
 }

fs/f2fs/file.c

@@ -2184,6 +2184,49 @@ static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
 	return err;
 }
 
+static int f2fs_ioc_get_encryption_policy_ex(struct file *filp,
+					     unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_get_policy_ex(filp, (void __user *)arg);
+}
+
+static int f2fs_ioc_add_encryption_key(struct file *filp, unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_add_key(filp, (void __user *)arg);
+}
+
+static int f2fs_ioc_remove_encryption_key(struct file *filp, unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_remove_key(filp, (void __user *)arg);
+}
+
+static int f2fs_ioc_remove_encryption_key_all_users(struct file *filp,
+						    unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_remove_key_all_users(filp, (void __user *)arg);
+}
+
+static int f2fs_ioc_get_encryption_key_status(struct file *filp,
+					      unsigned long arg)
+{
+	if (!f2fs_sb_has_encrypt(F2FS_I_SB(file_inode(filp))))
+		return -EOPNOTSUPP;
+
+	return fscrypt_ioctl_get_key_status(filp, (void __user *)arg);
+}
+
 static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
@@ -3092,6 +3135,16 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return f2fs_ioc_get_encryption_policy(filp, arg);
 	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
 		return f2fs_ioc_get_encryption_pwsalt(filp, arg);
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		return f2fs_ioc_get_encryption_policy_ex(filp, arg);
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		return f2fs_ioc_add_encryption_key(filp, arg);
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		return f2fs_ioc_remove_encryption_key(filp, arg);
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+		return f2fs_ioc_remove_encryption_key_all_users(filp, arg);
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		return f2fs_ioc_get_encryption_key_status(filp, arg);
 	case F2FS_IOC_GARBAGE_COLLECT:
 		return f2fs_ioc_gc(filp, arg);
 	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
@@ -3219,6 +3272,11 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case F2FS_IOC_SET_ENCRYPTION_POLICY:
 	case F2FS_IOC_GET_ENCRYPTION_PWSALT:
 	case F2FS_IOC_GET_ENCRYPTION_POLICY:
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
 	case F2FS_IOC_GARBAGE_COLLECT:
 	case F2FS_IOC_GARBAGE_COLLECT_RANGE:
 	case F2FS_IOC_WRITE_CHECKPOINT:

fs/f2fs/super.c

@@ -913,6 +913,8 @@ static int f2fs_drop_inode(struct inode *inode)
 		return 0;
 	}
 	ret = generic_drop_inode(inode);
+	if (!ret)
+		ret = fscrypt_drop_inode(inode);
 	trace_f2fs_drop_inode(inode, ret);
 	return ret;
 }

fs/super.c

@@ -32,6 +32,7 @@
 #include <linux/backing-dev.h>
 #include <linux/rculist_bl.h>
 #include <linux/cleancache.h>
+#include <linux/fscrypt.h>
 #include <linux/fsnotify.h>
 #include <linux/lockdep.h>
 #include <linux/user_namespace.h>
@@ -290,6 +291,7 @@ static void __put_super(struct super_block *s)
 		WARN_ON(s->s_inode_lru.node);
 		WARN_ON(!list_empty(&s->s_mounts));
 		security_sb_free(s);
+		fscrypt_sb_free(s);
 		put_user_ns(s->s_user_ns);
 		kfree(s->s_subtype);
 		call_rcu(&s->rcu, destroy_super_rcu);

fs/ubifs/ioctl.c

@@ -185,6 +185,21 @@ long ubifs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	case FS_IOC_GET_ENCRYPTION_POLICY:
 		return fscrypt_ioctl_get_policy(file, (void __user *)arg);
 
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+		return fscrypt_ioctl_get_policy_ex(file, (void __user *)arg);
+
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+		return fscrypt_ioctl_add_key(file, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+		return fscrypt_ioctl_remove_key(file, (void __user *)arg);
+
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+		return fscrypt_ioctl_remove_key_all_users(file,
+							  (void __user *)arg);
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
+		return fscrypt_ioctl_get_key_status(file, (void __user *)arg);
+
 	default:
 		return -ENOTTY;
 	}
@@ -202,6 +217,11 @@ long ubifs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		break;
 	case FS_IOC_SET_ENCRYPTION_POLICY:
 	case FS_IOC_GET_ENCRYPTION_POLICY:
+	case FS_IOC_GET_ENCRYPTION_POLICY_EX:
+	case FS_IOC_ADD_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY:
+	case FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS:
+	case FS_IOC_GET_ENCRYPTION_KEY_STATUS:
 		break;
 	default:
 		return -ENOIOCTLCMD;

fs/ubifs/super.c

@@ -318,6 +318,16 @@ static int ubifs_write_inode(struct inode *inode, struct writeback_control *wbc)
 	return err;
 }
 
+static int ubifs_drop_inode(struct inode *inode)
+{
+	int drop = generic_drop_inode(inode);
+
+	if (!drop)
+		drop = fscrypt_drop_inode(inode);
+
+	return drop;
+}
+
 static void ubifs_evict_inode(struct inode *inode)
 {
 	int err;
@@ -1994,6 +2004,7 @@ const struct super_operations ubifs_super_operations = {
 	.free_inode    = ubifs_free_inode,
 	.put_super     = ubifs_put_super,
 	.write_inode   = ubifs_write_inode,
+	.drop_inode    = ubifs_drop_inode,
 	.evict_inode   = ubifs_evict_inode,
 	.statfs        = ubifs_statfs,
 	.dirty_inode   = ubifs_dirty_inode,

include/linux/fs.h

@@ -1427,6 +1427,7 @@ struct super_block {
 	const struct xattr_handler **s_xattr;
 #ifdef CONFIG_FS_ENCRYPTION
 	const struct fscrypt_operations	*s_cop;
+	struct key		*s_master_keys; /* master crypto keys in use */
 #endif
 	struct hlist_bl_head	s_roots;	/* alternate root dentries for NFS */
 	struct list_head	s_mounts;	/* list of mounts; _not_ for fs use */

include/linux/fscrypt.h

@@ -16,6 +16,7 @@
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/slab.h>
+#include <uapi/linux/fscrypt.h>
 
 #define FS_CRYPTO_BLOCK_SIZE		16
 
@@ -42,7 +43,7 @@ struct fscrypt_name {
 #define fname_len(p)		((p)->disk_name.len)
 
 /* Maximum value for the third parameter of fscrypt_operations.set_context(). */
-#define FSCRYPT_SET_CONTEXT_MAX_SIZE	28
+#define FSCRYPT_SET_CONTEXT_MAX_SIZE	40
 
 #ifdef CONFIG_FS_ENCRYPTION
 /*
@@ -134,13 +135,23 @@ extern void fscrypt_free_bounce_page(struct page *bounce_page);
 /* policy.c */
 extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
 extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
+extern int fscrypt_ioctl_get_policy_ex(struct file *, void __user *);
 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 					void *, bool);
-/* keyinfo.c */
+/* keyring.c */
+extern void fscrypt_sb_free(struct super_block *sb);
+extern int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
+extern int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg);
+extern int fscrypt_ioctl_remove_key_all_users(struct file *filp,
+					      void __user *arg);
+extern int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg);
+
+/* keysetup.c */
 extern int fscrypt_get_encryption_info(struct inode *);
 extern void fscrypt_put_encryption_info(struct inode *);
 extern void fscrypt_free_inode(struct inode *);
+extern int fscrypt_drop_inode(struct inode *inode);
 
 /* fname.c */
 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
@@ -353,6 +364,12 @@ static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 	return -EOPNOTSUPP;
 }
 
+static inline int fscrypt_ioctl_get_policy_ex(struct file *filp,
+					      void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int fscrypt_has_permitted_context(struct inode *parent,
 						struct inode *child)
 {
@@ -366,7 +383,34 @@ static inline int fscrypt_inherit_context(struct inode *parent,
 	return -EOPNOTSUPP;
 }
 
-/* keyinfo.c */
+/* keyring.c */
+static inline void fscrypt_sb_free(struct super_block *sb)
+{
+}
+
+static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int fscrypt_ioctl_remove_key_all_users(struct file *filp,
+						     void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int fscrypt_ioctl_get_key_status(struct file *filp,
+					       void __user *arg)
+{
+	return -EOPNOTSUPP;
+}
+
+/* keysetup.c */
 static inline int fscrypt_get_encryption_info(struct inode *inode)
 {
 	return -EOPNOTSUPP;
@@ -381,6 +425,11 @@ static inline void fscrypt_free_inode(struct inode *inode)
 {
 }
 
+static inline int fscrypt_drop_inode(struct inode *inode)
+{
+	return 0;
+}
+
  /* fname.c */
 static inline int fscrypt_setup_filename(struct inode *dir,
 					 const struct qstr *iname,

include/uapi/linux/fs.h

@@ -13,6 +13,9 @@
 #include <linux/limits.h>
 #include <linux/ioctl.h>
 #include <linux/types.h>
+#ifndef __KERNEL__
+#include <linux/fscrypt.h>
+#endif
 
 /* Use of MS_* flags within the kernel is restricted to core mount(2) code. */
 #if !defined(__KERNEL__)
@@ -212,57 +215,6 @@ struct fsxattr {
 #define FS_IOC_GETFSLABEL		_IOR(0x94, 49, char[FSLABEL_MAX])
 #define FS_IOC_SETFSLABEL		_IOW(0x94, 50, char[FSLABEL_MAX])
 
-/*
- * File system encryption support
- */
-/* Policy provided via an ioctl on the topmost directory */
-#define FS_KEY_DESCRIPTOR_SIZE	8
-
-#define FS_POLICY_FLAGS_PAD_4		0x00
-#define FS_POLICY_FLAGS_PAD_8		0x01
-#define FS_POLICY_FLAGS_PAD_16		0x02
-#define FS_POLICY_FLAGS_PAD_32		0x03
-#define FS_POLICY_FLAGS_PAD_MASK	0x03
-#define FS_POLICY_FLAG_DIRECT_KEY	0x04	/* use master key directly */
-#define FS_POLICY_FLAGS_VALID		0x07
-
-/* Encryption algorithms */
-#define FS_ENCRYPTION_MODE_INVALID		0
-#define FS_ENCRYPTION_MODE_AES_256_XTS		1
-#define FS_ENCRYPTION_MODE_AES_256_GCM		2
-#define FS_ENCRYPTION_MODE_AES_256_CBC		3
-#define FS_ENCRYPTION_MODE_AES_256_CTS		4
-#define FS_ENCRYPTION_MODE_AES_128_CBC		5
-#define FS_ENCRYPTION_MODE_AES_128_CTS		6
-#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8 /* Removed, do not use. */
-#define FS_ENCRYPTION_MODE_ADIANTUM		9
-
-struct fscrypt_policy {
-	__u8 version;
-	__u8 contents_encryption_mode;
-	__u8 filenames_encryption_mode;
-	__u8 flags;
-	__u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
-};
-
-#define FS_IOC_SET_ENCRYPTION_POLICY	_IOR('f', 19, struct fscrypt_policy)
-#define FS_IOC_GET_ENCRYPTION_PWSALT	_IOW('f', 20, __u8[16])
-#define FS_IOC_GET_ENCRYPTION_POLICY	_IOW('f', 21, struct fscrypt_policy)
-
-/* Parameters for passing an encryption key into the kernel keyring */
-#define FS_KEY_DESC_PREFIX		"fscrypt:"
-#define FS_KEY_DESC_PREFIX_SIZE		8
-
-/* Structure that userspace passes to the kernel keyring */
-#define FS_MAX_KEY_SIZE			64
-
-struct fscrypt_key {
-	__u32 mode;
-	__u8 raw[FS_MAX_KEY_SIZE];
-	__u32 size;
-};
-
 /*
  * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)
  *

include/uapi/linux/fscrypt.h

+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * fscrypt user API
+ *
+ * These ioctls can be used on filesystems that support fscrypt.  See the
+ * "User API" section of Documentation/filesystems/fscrypt.rst.
+ */
+#ifndef _UAPI_LINUX_FSCRYPT_H
+#define _UAPI_LINUX_FSCRYPT_H
+
+#include <linux/types.h>
+
+/* Encryption policy flags */
+#define FSCRYPT_POLICY_FLAGS_PAD_4		0x00
+#define FSCRYPT_POLICY_FLAGS_PAD_8		0x01
+#define FSCRYPT_POLICY_FLAGS_PAD_16		0x02
+#define FSCRYPT_POLICY_FLAGS_PAD_32		0x03
+#define FSCRYPT_POLICY_FLAGS_PAD_MASK		0x03
+#define FSCRYPT_POLICY_FLAG_DIRECT_KEY		0x04
+#define FSCRYPT_POLICY_FLAGS_VALID		0x07
+
+/* Encryption algorithms */
+#define FSCRYPT_MODE_AES_256_XTS		1
+#define FSCRYPT_MODE_AES_256_CTS		4
+#define FSCRYPT_MODE_AES_128_CBC		5
+#define FSCRYPT_MODE_AES_128_CTS		6
+#define FSCRYPT_MODE_ADIANTUM			9
+#define __FSCRYPT_MODE_MAX			9
+
+/*
+ * Legacy policy version; ad-hoc KDF and no key verification.
+ * For new encrypted directories, use fscrypt_policy_v2 instead.
+ *
+ * Careful: the .version field for this is actually 0, not 1.
+ */
+#define FSCRYPT_POLICY_V1		0
+#define FSCRYPT_KEY_DESCRIPTOR_SIZE	8
+struct fscrypt_policy_v1 {
+	__u8 version;
+	__u8 contents_encryption_mode;
+	__u8 filenames_encryption_mode;
+	__u8 flags;
+	__u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+};
+#define fscrypt_policy	fscrypt_policy_v1
+
+/*
+ * Process-subscribed "logon" key description prefix and payload format.
+ * Deprecated; prefer FS_IOC_ADD_ENCRYPTION_KEY instead.
+ */
+#define FSCRYPT_KEY_DESC_PREFIX		"fscrypt:"
+#define FSCRYPT_KEY_DESC_PREFIX_SIZE	8
+#define FSCRYPT_MAX_KEY_SIZE		64
+struct fscrypt_key {
+	__u32 mode;
+	__u8 raw[FSCRYPT_MAX_KEY_SIZE];
+	__u32 size;
+};
+
+/*
+ * New policy version with HKDF and key verification (recommended).
+ */
+#define FSCRYPT_POLICY_V2		2
+#define FSCRYPT_KEY_IDENTIFIER_SIZE	16
+struct fscrypt_policy_v2 {
+	__u8 version;
+	__u8 contents_encryption_mode;
+	__u8 filenames_encryption_mode;
+	__u8 flags;
+	__u8 __reserved[4];
+	__u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+};
+
+/* Struct passed to FS_IOC_GET_ENCRYPTION_POLICY_EX */
+struct fscrypt_get_policy_ex_arg {
+	__u64 policy_size; /* input/output */
+	union {
+		__u8 version;
+		struct fscrypt_policy_v1 v1;
+		struct fscrypt_policy_v2 v2;
+	} policy; /* output */
+};
+
+/*
+ * v1 policy keys are specified by an arbitrary 8-byte key "descriptor",
+ * matching fscrypt_policy_v1::master_key_descriptor.
+ */
+#define FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR	1
+
+/*
+ * v2 policy keys are specified by a 16-byte key "identifier" which the kernel
+ * calculates as a cryptographic hash of the key itself,
+ * matching fscrypt_policy_v2::master_key_identifier.
+ */
+#define FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER	2
+
+/*
+ * Specifies a key, either for v1 or v2 policies.  This doesn't contain the
+ * actual key itself; this is just the "name" of the key.
+ */
+struct fscrypt_key_specifier {
+	__u32 type;	/* one of FSCRYPT_KEY_SPEC_TYPE_* */
+	__u32 __reserved;
+	union {
+		__u8 __reserved[32]; /* reserve some extra space */
+		__u8 descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
+		__u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
+	} u;
+};
+
+/* Struct passed to FS_IOC_ADD_ENCRYPTION_KEY */
+struct fscrypt_add_key_arg {
+	struct fscrypt_key_specifier key_spec;
+	__u32 raw_size;
+	__u32 __reserved[9];
+	__u8 raw[];
+};
+
+/* Struct passed to FS_IOC_REMOVE_ENCRYPTION_KEY */
+struct fscrypt_remove_key_arg {
+	struct fscrypt_key_specifier key_spec;
+#define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY	0x00000001
+#define FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS	0x00000002
+	__u32 removal_status_flags;	/* output */
+	__u32 __reserved[5];
+};
+
+/* Struct passed to FS_IOC_GET_ENCRYPTION_KEY_STATUS */
+struct fscrypt_get_key_status_arg {
+	/* input */
+	struct fscrypt_key_specifier key_spec;
+	__u32 __reserved[6];
+
+	/* output */
+#define FSCRYPT_KEY_STATUS_ABSENT		1
+#define FSCRYPT_KEY_STATUS_PRESENT		2
+#define FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED	3
+	__u32 status;
+#define FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF   0x00000001
+	__u32 status_flags;
+	__u32 user_count;
+	__u32 __out_reserved[13];
+};
+
+#define FS_IOC_SET_ENCRYPTION_POLICY		_IOR('f', 19, struct fscrypt_policy)
+#define FS_IOC_GET_ENCRYPTION_PWSALT		_IOW('f', 20, __u8[16])
+#define FS_IOC_GET_ENCRYPTION_POLICY		_IOW('f', 21, struct fscrypt_policy)
+#define FS_IOC_GET_ENCRYPTION_POLICY_EX		_IOWR('f', 22, __u8[9]) /* size + version */
+#define FS_IOC_ADD_ENCRYPTION_KEY		_IOWR('f', 23, struct fscrypt_add_key_arg)
+#define FS_IOC_REMOVE_ENCRYPTION_KEY		_IOWR('f', 24, struct fscrypt_remove_key_arg)
+#define FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS	_IOWR('f', 25, struct fscrypt_remove_key_arg)
+#define FS_IOC_GET_ENCRYPTION_KEY_STATUS	_IOWR('f', 26, struct fscrypt_get_key_status_arg)
+
+/**********************************************************************/
+
+/* old names; don't add anything new here! */
+#ifndef __KERNEL__
+#define FS_KEY_DESCRIPTOR_SIZE		FSCRYPT_KEY_DESCRIPTOR_SIZE
+#define FS_POLICY_FLAGS_PAD_4		FSCRYPT_POLICY_FLAGS_PAD_4
+#define FS_POLICY_FLAGS_PAD_8		FSCRYPT_POLICY_FLAGS_PAD_8
+#define FS_POLICY_FLAGS_PAD_16		FSCRYPT_POLICY_FLAGS_PAD_16
+#define FS_POLICY_FLAGS_PAD_32		FSCRYPT_POLICY_FLAGS_PAD_32
+#define FS_POLICY_FLAGS_PAD_MASK	FSCRYPT_POLICY_FLAGS_PAD_MASK
+#define FS_POLICY_FLAG_DIRECT_KEY	FSCRYPT_POLICY_FLAG_DIRECT_KEY
+#define FS_POLICY_FLAGS_VALID		FSCRYPT_POLICY_FLAGS_VALID
+#define FS_ENCRYPTION_MODE_INVALID	0	/* never used */
+#define FS_ENCRYPTION_MODE_AES_256_XTS	FSCRYPT_MODE_AES_256_XTS
+#define FS_ENCRYPTION_MODE_AES_256_GCM	2	/* never used */
+#define FS_ENCRYPTION_MODE_AES_256_CBC	3	/* never used */
+#define FS_ENCRYPTION_MODE_AES_256_CTS	FSCRYPT_MODE_AES_256_CTS
+#define FS_ENCRYPTION_MODE_AES_128_CBC	FSCRYPT_MODE_AES_128_CBC
+#define FS_ENCRYPTION_MODE_AES_128_CTS	FSCRYPT_MODE_AES_128_CTS
+#define FS_ENCRYPTION_MODE_SPECK128_256_XTS	7	/* removed */
+#define FS_ENCRYPTION_MODE_SPECK128_256_CTS	8	/* removed */
+#define FS_ENCRYPTION_MODE_ADIANTUM	FSCRYPT_MODE_ADIANTUM
+#define FS_KEY_DESC_PREFIX		FSCRYPT_KEY_DESC_PREFIX
+#define FS_KEY_DESC_PREFIX_SIZE		FSCRYPT_KEY_DESC_PREFIX_SIZE
+#define FS_MAX_KEY_SIZE			FSCRYPT_MAX_KEY_SIZE
+#endif /* !__KERNEL__ */
+
+#endif /* _UAPI_LINUX_FSCRYPT_H */