Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt

Pull fscrypt updates from Ted Ts'o:
 "Refactor support for encrypted symlinks to move common code to fscrypt"

Ted also points out about the merge:
 "This makes the f2fs symlink code use the fscrypt_encrypt_symlink()
  from the fscrypt tree. This will end up dropping the kzalloc() ->
  f2fs_kzalloc() change, which means the fscrypt-specific allocation
  won't get tested by f2fs's kmalloc error injection system; which is
  fine"

* tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt: (26 commits)
  fscrypt: fix build with pre-4.6 gcc versions
  fscrypt: remove 'ci' parameter from fscrypt_put_encryption_info()
  fscrypt: document symlink length restriction
  fscrypt: fix up fscrypt_fname_encrypted_size() for internal use
  fscrypt: define fscrypt_fname_alloc_buffer() to be for presented names
  fscrypt: calculate NUL-padding length in one place only
  fscrypt: move fscrypt_symlink_data to fscrypt_private.h
  fscrypt: remove fscrypt_fname_usr_to_disk()
  ubifs: switch to fscrypt_get_symlink()
  ubifs: switch to fscrypt ->symlink() helper functions
  ubifs: free the encrypted symlink target
  f2fs: switch to fscrypt_get_symlink()
  f2fs: switch to fscrypt ->symlink() helper functions
  ext4: switch to fscrypt_get_symlink()
  ext4: switch to fscrypt ->symlink() helper functions
  fscrypt: new helper function - fscrypt_get_symlink()
  fscrypt: new helper functions for ->symlink()
  fscrypt: trim down fscrypt.h includes
  fscrypt: move fscrypt_is_dot_dotdot() to fs/crypto/fname.c
  fscrypt: move fscrypt_valid_enc_modes() to fscrypt_private.h
  ...

Documentation/filesystems/fscrypt.rst

@@ -448,8 +448,14 @@ astute users may notice some differences in behavior:
 
 - The st_size of an encrypted symlink will not necessarily give the
   length of the symlink target as required by POSIX.  It will actually
-  give the length of the ciphertext, which may be slightly longer than
-  the plaintext due to the NUL-padding.
+  give the length of the ciphertext, which will be slightly longer
+  than the plaintext due to NUL-padding and an extra 2-byte overhead.
+
+- The maximum length of an encrypted symlink is 2 bytes shorter than
+  the maximum length of an unencrypted symlink.  For example, on an
+  EXT4 filesystem with a 4K block size, unencrypted symlinks can be up
+  to 4095 bytes long, while encrypted symlinks can only be up to 4093
+  bytes long (both lengths excluding the terminating null).
 
 Note that mmap *is* supported.  This is possible because the pagecache
 for an encrypted file contains the plaintext, not the ciphertext.

fs/crypto/crypto.c

@@ -27,6 +27,7 @@
 #include <linux/dcache.h>
 #include <linux/namei.h>
 #include <crypto/aes.h>
+#include <crypto/skcipher.h>
 #include "fscrypt_private.h"
 
 static unsigned int num_prealloc_crypto_pages = 32;

fs/crypto/fname.c

@@ -13,42 +13,46 @@
 
 #include <linux/scatterlist.h>
 #include <linux/ratelimit.h>
+#include <crypto/skcipher.h>
 #include "fscrypt_private.h"
 
+static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
+{
+	if (str->len == 1 && str->name[0] == '.')
+		return true;
+
+	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
+		return true;
+
+	return false;
+}
+
 /**
  * fname_encrypt() - encrypt a filename
  *
- * The caller must have allocated sufficient memory for the @oname string.
+ * The output buffer must be at least as large as the input buffer.
+ * Any extra space is filled with NUL padding before encryption.
  *
  * Return: 0 on success, -errno on failure
  */
-static int fname_encrypt(struct inode *inode,
-			const struct qstr *iname, struct fscrypt_str *oname)
+int fname_encrypt(struct inode *inode, const struct qstr *iname,
+		  u8 *out, unsigned int olen)
 {
 	struct skcipher_request *req = NULL;
 	DECLARE_CRYPTO_WAIT(wait);
-	struct fscrypt_info *ci = inode->i_crypt_info;
-	struct crypto_skcipher *tfm = ci->ci_ctfm;
+	struct crypto_skcipher *tfm = inode->i_crypt_info->ci_ctfm;
 	int res = 0;
 	char iv[FS_CRYPTO_BLOCK_SIZE];
 	struct scatterlist sg;
-	int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
-	unsigned int lim;
-	unsigned int cryptlen;
-
-	lim = inode->i_sb->s_cop->max_namelen(inode);
-	if (iname->len <= 0 || iname->len > lim)
-		return -EIO;
 
 	/*
 	 * Copy the filename to the output buffer for encrypting in-place and
 	 * pad it with the needed number of NUL bytes.
 	 */
-	cryptlen = max_t(unsigned int, iname->len, FS_CRYPTO_BLOCK_SIZE);
-	cryptlen = round_up(cryptlen, padding);
-	cryptlen = min(cryptlen, lim);
-	memcpy(oname->name, iname->name, iname->len);
-	memset(oname->name + iname->len, 0, cryptlen - iname->len);
+	if (WARN_ON(olen < iname->len))
+		return -ENOBUFS;
+	memcpy(out, iname->name, iname->len);
+	memset(out + iname->len, 0, olen - iname->len);
 
 	/* Initialize the IV */
 	memset(iv, 0, FS_CRYPTO_BLOCK_SIZE);
@@ -63,8 +67,8 @@ static int fname_encrypt(struct inode *inode,
 	skcipher_request_set_callback(req,
 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
 			crypto_req_done, &wait);
-	sg_init_one(&sg, oname->name, cryptlen);
-	skcipher_request_set_crypt(req, &sg, &sg, cryptlen, iv);
+	sg_init_one(&sg, out, olen);
+	skcipher_request_set_crypt(req, &sg, &sg, olen, iv);
 
 	/* Do the encryption */
 	res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
@@ -75,7 +79,6 @@ static int fname_encrypt(struct inode *inode,
 		return res;
 	}
 
-	oname->len = cryptlen;
 	return 0;
 }
 
@@ -188,50 +191,52 @@ static int digest_decode(const char *src, int len, char *dst)
 	return cp - dst;
 }
 
-u32 fscrypt_fname_encrypted_size(const struct inode *inode, u32 ilen)
+bool fscrypt_fname_encrypted_size(const struct inode *inode, u32 orig_len,
+				  u32 max_len, u32 *encrypted_len_ret)
 {
-	int padding = 32;
-	struct fscrypt_info *ci = inode->i_crypt_info;
-
-	if (ci)
-		padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK);
-	ilen = max(ilen, (u32)FS_CRYPTO_BLOCK_SIZE);
-	return round_up(ilen, padding);
+	int padding = 4 << (inode->i_crypt_info->ci_flags &
+			    FS_POLICY_FLAGS_PAD_MASK);
+	u32 encrypted_len;
+
+	if (orig_len > max_len)
+		return false;
+	encrypted_len = max(orig_len, (u32)FS_CRYPTO_BLOCK_SIZE);
+	encrypted_len = round_up(encrypted_len, padding);
+	*encrypted_len_ret = min(encrypted_len, max_len);
+	return true;
 }
-EXPORT_SYMBOL(fscrypt_fname_encrypted_size);
 
 /**
- * fscrypt_fname_crypto_alloc_obuff() -
+ * fscrypt_fname_alloc_buffer - allocate a buffer for presented filenames
  *
- * Allocates an output buffer that is sufficient for the crypto operation
- * specified by the context and the direction.
+ * Allocate a buffer that is large enough to hold any decrypted or encoded
+ * filename (null-terminated), for the given maximum encrypted filename length.
+ *
+ * Return: 0 on success, -errno on failure
  */
 int fscrypt_fname_alloc_buffer(const struct inode *inode,
-				u32 ilen, struct fscrypt_str *crypto_str)
+			       u32 max_encrypted_len,
+			       struct fscrypt_str *crypto_str)
 {
-	u32 olen = fscrypt_fname_encrypted_size(inode, ilen);
 	const u32 max_encoded_len =
 		max_t(u32, BASE64_CHARS(FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE),
 		      1 + BASE64_CHARS(sizeof(struct fscrypt_digested_name)));
+	u32 max_presented_len;
 
-	crypto_str->len = olen;
-	olen = max(olen, max_encoded_len);
+	max_presented_len = max(max_encoded_len, max_encrypted_len);
 
-	/*
-	 * Allocated buffer can hold one more character to null-terminate the
-	 * string
-	 */
-	crypto_str->name = kmalloc(olen + 1, GFP_NOFS);
-	if (!(crypto_str->name))
+	crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS);
+	if (!crypto_str->name)
 		return -ENOMEM;
+	crypto_str->len = max_presented_len;
 	return 0;
 }
 EXPORT_SYMBOL(fscrypt_fname_alloc_buffer);
 
 /**
- * fscrypt_fname_crypto_free_buffer() -
+ * fscrypt_fname_free_buffer - free the buffer for presented filenames
  *
- * Frees the buffer allocated for crypto operation.
+ * Free the buffer allocated by fscrypt_fname_alloc_buffer().
  */
 void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
 {
@@ -297,35 +302,6 @@ int fscrypt_fname_disk_to_usr(struct inode *inode,
 }
 EXPORT_SYMBOL(fscrypt_fname_disk_to_usr);
 
-/**
- * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk
- * space
- *
- * The caller must have allocated sufficient memory for the @oname string.
- *
- * Return: 0 on success, -errno on failure
- */
-int fscrypt_fname_usr_to_disk(struct inode *inode,
-			const struct qstr *iname,
-			struct fscrypt_str *oname)
-{
-	if (fscrypt_is_dot_dotdot(iname)) {
-		oname->name[0] = '.';
-		oname->name[iname->len - 1] = '.';
-		oname->len = iname->len;
-		return 0;
-	}
-	if (inode->i_crypt_info)
-		return fname_encrypt(inode, iname, oname);
-	/*
-	 * Without a proper key, a user is not allowed to modify the filenames
-	 * in a directory. Consequently, a user space name cannot be mapped to
-	 * a disk-space name
-	 */
-	return -ENOKEY;
-}
-EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
-
 /**
  * fscrypt_setup_filename() - prepare to search a possibly encrypted directory
  * @dir: the directory that will be searched
@@ -369,11 +345,17 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 		return ret;
 
 	if (dir->i_crypt_info) {
-		ret = fscrypt_fname_alloc_buffer(dir, iname->len,
-							&fname->crypto_buf);
-		if (ret)
-			return ret;
-		ret = fname_encrypt(dir, iname, &fname->crypto_buf);
+		if (!fscrypt_fname_encrypted_size(dir, iname->len,
+						  dir->i_sb->s_cop->max_namelen(dir),
+						  &fname->crypto_buf.len))
+			return -ENAMETOOLONG;
+		fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,
+						 GFP_NOFS);
+		if (!fname->crypto_buf.name)
+			return -ENOMEM;
+
+		ret = fname_encrypt(dir, iname, fname->crypto_buf.name,
+				    fname->crypto_buf.len);
 		if (ret)
 			goto errout;
 		fname->disk_name.name = fname->crypto_buf.name;
@@ -425,7 +407,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 	return 0;
 
 errout:
-	fscrypt_fname_free_buffer(&fname->crypto_buf);
+	kfree(fname->crypto_buf.name);
 	return ret;
 }
 EXPORT_SYMBOL(fscrypt_setup_filename);

fs/crypto/fscrypt_private.h

@@ -50,6 +50,15 @@ struct fscrypt_context {
 
 #define FS_ENCRYPTION_CONTEXT_FORMAT_V1		1
 
+/**
+ * For encrypted symlinks, the ciphertext length is stored at the beginning
+ * of the string in little-endian format.
+ */
+struct fscrypt_symlink_data {
+	__le16 len;
+	char encrypted_path[1];
+} __packed;
+
 /*
  * A pointer to this structure is stored in the file system's in-core
  * representation of an inode.
@@ -71,7 +80,22 @@ typedef enum {
 #define FS_CTX_REQUIRES_FREE_ENCRYPT_FL		0x00000001
 #define FS_CTX_HAS_BOUNCE_BUFFER_FL		0x00000002
 
+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)
+		return true;
+
+	if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS &&
+	    filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS)
+		return true;
+
+	return false;
+}
+
 /* crypto.c */
+extern struct kmem_cache *fscrypt_info_cachep;
 extern int fscrypt_initialize(unsigned int cop_flags);
 extern struct workqueue_struct *fscrypt_read_workqueue;
 extern int fscrypt_do_page_crypto(const struct inode *inode,
@@ -83,6 +107,13 @@ extern int fscrypt_do_page_crypto(const struct inode *inode,
 extern struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
 					      gfp_t gfp_flags);
 
+/* fname.c */
+extern int fname_encrypt(struct inode *inode, const struct qstr *iname,
+			 u8 *out, unsigned int olen);
+extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
+					 u32 orig_len, u32 max_len,
+					 u32 *encrypted_len_ret);
+
 /* keyinfo.c */
 extern void __exit fscrypt_essiv_cleanup(void);
 

fs/crypto/hooks.c

@@ -110,3 +110,161 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);
+
+int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
+			      unsigned int max_len,
+			      struct fscrypt_str *disk_link)
+{
+	int err;
+
+	/*
+	 * To calculate the size of the encrypted symlink target we need to know
+	 * the amount of NUL padding, which is determined by the flags set in
+	 * the encryption policy which will be inherited from the directory.
+	 * The easiest way to get access to this is to just load the directory's
+	 * fscrypt_info, since we'll need it to create the dir_entry anyway.
+	 *
+	 * Note: in test_dummy_encryption mode, @dir may be unencrypted.
+	 */
+	err = fscrypt_get_encryption_info(dir);
+	if (err)
+		return err;
+	if (!fscrypt_has_encryption_key(dir))
+		return -ENOKEY;
+
+	/*
+	 * Calculate the size of the encrypted symlink and verify it won't
+	 * exceed max_len.  Note that for historical reasons, encrypted symlink
+	 * targets are prefixed with the ciphertext length, despite this
+	 * actually being redundant with i_size.  This decreases by 2 bytes the
+	 * longest symlink target we can accept.
+	 *
+	 * We could recover 1 byte by not counting a null terminator, but
+	 * counting it (even though it is meaningless for ciphertext) is simpler
+	 * for now since filesystems will assume it is there and subtract it.
+	 */
+	if (!fscrypt_fname_encrypted_size(dir, len,
+					  max_len - sizeof(struct fscrypt_symlink_data),
+					  &disk_link->len))
+		return -ENAMETOOLONG;
+	disk_link->len += sizeof(struct fscrypt_symlink_data);
+
+	disk_link->name = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__fscrypt_prepare_symlink);
+
+int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
+			      unsigned int len, struct fscrypt_str *disk_link)
+{
+	int err;
+	struct qstr iname = QSTR_INIT(target, len);
+	struct fscrypt_symlink_data *sd;
+	unsigned int ciphertext_len;
+
+	err = fscrypt_require_key(inode);
+	if (err)
+		return err;
+
+	if (disk_link->name) {
+		/* filesystem-provided buffer */
+		sd = (struct fscrypt_symlink_data *)disk_link->name;
+	} else {
+		sd = kmalloc(disk_link->len, GFP_NOFS);
+		if (!sd)
+			return -ENOMEM;
+	}
+	ciphertext_len = disk_link->len - sizeof(*sd);
+	sd->len = cpu_to_le16(ciphertext_len);
+
+	err = fname_encrypt(inode, &iname, sd->encrypted_path, ciphertext_len);
+	if (err) {
+		if (!disk_link->name)
+			kfree(sd);
+		return err;
+	}
+	/*
+	 * Null-terminating the ciphertext doesn't make sense, but we still
+	 * count the null terminator in the length, so we might as well
+	 * initialize it just in case the filesystem writes it out.
+	 */
+	sd->encrypted_path[ciphertext_len] = '\0';
+
+	if (!disk_link->name)
+		disk_link->name = (unsigned char *)sd;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__fscrypt_encrypt_symlink);
+
+/**
+ * fscrypt_get_symlink - get the target of an encrypted symlink
+ * @inode: the symlink inode
+ * @caddr: the on-disk contents of the symlink
+ * @max_size: size of @caddr buffer
+ * @done: if successful, will be set up to free the returned target
+ *
+ * If the symlink's encryption key is available, we decrypt its target.
+ * Otherwise, we encode its target for presentation.
+ *
+ * This may sleep, so the filesystem must have dropped out of RCU mode already.
+ *
+ * Return: the presentable symlink target or an ERR_PTR()
+ */
+const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
+				unsigned int max_size,
+				struct delayed_call *done)
+{
+	const struct fscrypt_symlink_data *sd;
+	struct fscrypt_str cstr, pstr;
+	int err;
+
+	/* This is for encrypted symlinks only */
+	if (WARN_ON(!IS_ENCRYPTED(inode)))
+		return ERR_PTR(-EINVAL);
+
+	/*
+	 * Try to set up the symlink's encryption key, but we can continue
+	 * regardless of whether the key is available or not.
+	 */
+	err = fscrypt_get_encryption_info(inode);
+	if (err)
+		return ERR_PTR(err);
+
+	/*
+	 * For historical reasons, encrypted symlink targets are prefixed with
+	 * the ciphertext length, even though this is redundant with i_size.
+	 */
+
+	if (max_size < sizeof(*sd))
+		return ERR_PTR(-EUCLEAN);
+	sd = caddr;
+	cstr.name = (unsigned char *)sd->encrypted_path;
+	cstr.len = le16_to_cpu(sd->len);
+
+	if (cstr.len == 0)
+		return ERR_PTR(-EUCLEAN);
+
+	if (cstr.len + sizeof(*sd) - 1 > max_size)
+		return ERR_PTR(-EUCLEAN);
+
+	err = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr);
+	if (err)
+		return ERR_PTR(err);
+
+	err = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
+	if (err)
+		goto err_kfree;
+
+	err = -EUCLEAN;
+	if (pstr.name[0] == '\0')
+		goto err_kfree;
+
+	pstr.name[pstr.len] = '\0';
+	set_delayed_call(done, kfree_link, pstr.name);
+	return pstr.name;
+
+err_kfree:
+	kfree(pstr.name);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(fscrypt_get_symlink);

fs/crypto/keyinfo.c

@@ -14,6 +14,7 @@
 #include <linux/ratelimit.h>
 #include <crypto/aes.h>
 #include <crypto/sha.h>
+#include <crypto/skcipher.h>
 #include "fscrypt_private.h"
 
 static struct crypto_shash *essiv_hash_tfm;
@@ -354,19 +355,9 @@ int fscrypt_get_encryption_info(struct inode *inode)
 }
 EXPORT_SYMBOL(fscrypt_get_encryption_info);
 
-void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
+void fscrypt_put_encryption_info(struct inode *inode)
 {
-	struct fscrypt_info *prev;
-
-	if (ci == NULL)
-		ci = READ_ONCE(inode->i_crypt_info);
-	if (ci == NULL)
-		return;
-
-	prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
-	if (prev != ci)
-		return;
-
-	put_crypt_info(ci);
+	put_crypt_info(inode->i_crypt_info);
+	inode->i_crypt_info = NULL;
 }
 EXPORT_SYMBOL(fscrypt_put_encryption_info);

fs/ext4/namei.c

@@ -3057,39 +3057,19 @@ static int ext4_symlink(struct inode *dir,
 	struct inode *inode;
 	int err, len = strlen(symname);
 	int credits;
-	bool encryption_required;
 	struct fscrypt_str disk_link;
-	struct fscrypt_symlink_data *sd = NULL;
 
 	if (unlikely(ext4_forced_shutdown(EXT4_SB(dir->i_sb))))
 		return -EIO;
 
-	disk_link.len = len + 1;
-	disk_link.name = (char *) symname;
-
-	encryption_required = (ext4_encrypted_inode(dir) ||
-			       DUMMY_ENCRYPTION_ENABLED(EXT4_SB(dir->i_sb)));
-	if (encryption_required) {
-		err = fscrypt_get_encryption_info(dir);
+	err = fscrypt_prepare_symlink(dir, symname, len, dir->i_sb->s_blocksize,
+				      &disk_link);
 	if (err)
 		return err;
-		if (!fscrypt_has_encryption_key(dir))
-			return -ENOKEY;
-		disk_link.len = (fscrypt_fname_encrypted_size(dir, len) +
-				 sizeof(struct fscrypt_symlink_data));
-		sd = kzalloc(disk_link.len, GFP_KERNEL);
-		if (!sd)
-			return -ENOMEM;
-	}
-
-	if (disk_link.len > dir->i_sb->s_blocksize) {
-		err = -ENAMETOOLONG;
-		goto err_free_sd;
-	}
 
 	err = dquot_initialize(dir);
 	if (err)
-		goto err_free_sd;
+		return err;
 
 	if ((disk_link.len > EXT4_N_BLOCKS * 4)) {
 		/*
@@ -3118,27 +3098,18 @@ static int ext4_symlink(struct inode *dir,
 	if (IS_ERR(inode)) {
 		if (handle)
 			ext4_journal_stop(handle);
-		err = PTR_ERR(inode);
-		goto err_free_sd;
+		return PTR_ERR(inode);
 	}
 
-	if (encryption_required) {
-		struct qstr istr;
-		struct fscrypt_str ostr =
-			FSTR_INIT(sd->encrypted_path, disk_link.len);
-
-		istr.name = (const unsigned char *) symname;
-		istr.len = len;
-		err = fscrypt_fname_usr_to_disk(inode, &istr, &ostr);
+	if (IS_ENCRYPTED(inode)) {
+		err = fscrypt_encrypt_symlink(inode, symname, len, &disk_link);
 		if (err)
 			goto err_drop_inode;
-		sd->len = cpu_to_le16(ostr.len);
-		disk_link.name = (char *) sd;
 		inode->i_op = &ext4_encrypted_symlink_inode_operations;
 	}
 
 	if ((disk_link.len > EXT4_N_BLOCKS * 4)) {
-		if (!encryption_required)
+		if (!IS_ENCRYPTED(inode))
 			inode->i_op = &ext4_symlink_inode_operations;
 		inode_nohighmem(inode);
 		ext4_set_aops(inode);
@@ -3180,7 +3151,7 @@ static int ext4_symlink(struct inode *dir,
 	} else {
 		/* clear the extent format for fast symlink */
 		ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
-		if (!encryption_required) {
+		if (!IS_ENCRYPTED(inode)) {
 			inode->i_op = &ext4_fast_symlink_inode_operations;
 			inode->i_link = (char *)&EXT4_I(inode)->i_data;
 		}
@@ -3195,16 +3166,17 @@ static int ext4_symlink(struct inode *dir,
 
 	if (handle)
 		ext4_journal_stop(handle);
-	kfree(sd);
-	return err;
+	goto out_free_encrypted_link;
+
 err_drop_inode:
 	if (handle)
 		ext4_journal_stop(handle);
 	clear_nlink(inode);
 	unlock_new_inode(inode);
 	iput(inode);
-err_free_sd:
-	kfree(sd);
+out_free_encrypted_link:
+	if (disk_link.name != (unsigned char *)symname)
+		kfree(disk_link.name);
 	return err;
 }
 

fs/ext4/super.c

@@ -1073,9 +1073,7 @@ void ext4_clear_inode(struct inode *inode)
 		jbd2_free_inode(EXT4_I(inode)->jinode);
 		EXT4_I(inode)->jinode = NULL;
 	}
-#ifdef CONFIG_EXT4_FS_ENCRYPTION
-	fscrypt_put_encryption_info(inode, NULL);
-#endif
+	fscrypt_put_encryption_info(inode);
 }
 
 static struct inode *ext4_nfs_get_inode(struct super_block *sb,

fs/ext4/symlink.c

@@ -28,59 +28,28 @@ static const char *ext4_encrypted_get_link(struct dentry *dentry,
 					   struct delayed_call *done)
 {
 	struct page *cpage = NULL;
-	char *caddr, *paddr = NULL;
-	struct fscrypt_str cstr, pstr;
-	struct fscrypt_symlink_data *sd;
-	int res;
-	u32 max_size = inode->i_sb->s_blocksize;
+	const void *caddr;
+	unsigned int max_size;
+	const char *paddr;
 
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
 
-	res = fscrypt_get_encryption_info(inode);
-	if (res)
-		return ERR_PTR(res);
-
 	if (ext4_inode_is_fast_symlink(inode)) {
-		caddr = (char *) EXT4_I(inode)->i_data;
+		caddr = EXT4_I(inode)->i_data;
 		max_size = sizeof(EXT4_I(inode)->i_data);
 	} else {
 		cpage = read_mapping_page(inode->i_mapping, 0, NULL);
 		if (IS_ERR(cpage))
 			return ERR_CAST(cpage);
 		caddr = page_address(cpage);
+		max_size = inode->i_sb->s_blocksize;
 	}
 
-	/* Symlink is encrypted */
-	sd = (struct fscrypt_symlink_data *)caddr;
-	cstr.name = sd->encrypted_path;
-	cstr.len  = le16_to_cpu(sd->len);
-	if ((cstr.len + sizeof(struct fscrypt_symlink_data) - 1) > max_size) {
-		/* Symlink data on the disk is corrupted */
-		res = -EFSCORRUPTED;
-		goto errout;
-	}
-
-	res = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr);
-	if (res)
-		goto errout;
-	paddr = pstr.name;
-
-	res = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
-	if (res)
-		goto errout;
-
-	/* Null-terminate the name */
-	paddr[pstr.len] = '\0';
+	paddr = fscrypt_get_symlink(inode, caddr, max_size, done);
 	if (cpage)
 		put_page(cpage);
-	set_delayed_call(done, kfree_link, paddr);
 	return paddr;
-errout:
-	if (cpage)
-		put_page(cpage);
-	kfree(paddr);
-	return ERR_PTR(res);
 }
 
 const struct inode_operations ext4_encrypted_symlink_inode_operations = {

fs/f2fs/inode.c

@@ -585,7 +585,7 @@ void f2fs_evict_inode(struct inode *inode)
 			!exist_written_data(sbi, inode->i_ino, ORPHAN_INO));
 	}
 out_clear:
-	fscrypt_put_encryption_info(inode, NULL);
+	fscrypt_put_encryption_info(inode);
 	clear_inode(inode);
 }
 

fs/f2fs/namei.c

@@ -486,28 +486,17 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 	struct f2fs_sb_info *sbi = F2FS_I_SB(dir);
 	struct inode *inode;
 	size_t len = strlen(symname);
-	struct fscrypt_str disk_link = FSTR_INIT((char *)symname, len + 1);
-	struct fscrypt_symlink_data *sd = NULL;
+	struct fscrypt_str disk_link;
 	int err;
 
 	if (unlikely(f2fs_cp_error(sbi)))
 		return -EIO;
 
-	if (f2fs_encrypted_inode(dir)) {
-		err = fscrypt_get_encryption_info(dir);
+	err = fscrypt_prepare_symlink(dir, symname, len, dir->i_sb->s_blocksize,
+				      &disk_link);
 	if (err)
 		return err;
 
-		if (!fscrypt_has_encryption_key(dir))
-			return -ENOKEY;
-
-		disk_link.len = (fscrypt_fname_encrypted_size(dir, len) +
-				sizeof(struct fscrypt_symlink_data));
-	}
-
-	if (disk_link.len > dir->i_sb->s_blocksize)
-		return -ENAMETOOLONG;
-
 	err = dquot_initialize(dir);
 	if (err)
 		return err;
@@ -516,7 +505,7 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 	if (IS_ERR(inode))
 		return PTR_ERR(inode);
 
-	if (f2fs_encrypted_inode(inode))
+	if (IS_ENCRYPTED(inode))
 		inode->i_op = &f2fs_encrypted_symlink_inode_operations;
 	else
 		inode->i_op = &f2fs_symlink_inode_operations;
@@ -526,39 +515,14 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 	f2fs_lock_op(sbi);
 	err = f2fs_add_link(dentry, inode);
 	if (err)
-		goto out;
+		goto out_handle_failed_inode;
 	f2fs_unlock_op(sbi);
 	alloc_nid_done(sbi, inode->i_ino);
 
-	if (f2fs_encrypted_inode(inode)) {
-		struct qstr istr = QSTR_INIT(symname, len);
-		struct fscrypt_str ostr;
-
-		sd = f2fs_kzalloc(sbi, disk_link.len, GFP_NOFS);
-		if (!sd) {
-			err = -ENOMEM;
-			goto err_out;
-		}
-
-		err = fscrypt_get_encryption_info(inode);
+	err = fscrypt_encrypt_symlink(inode, symname, len, &disk_link);
 	if (err)
 		goto err_out;
 
-		if (!fscrypt_has_encryption_key(inode)) {
-			err = -ENOKEY;
-			goto err_out;
-		}
-
-		ostr.name = sd->encrypted_path;
-		ostr.len = disk_link.len;
-		err = fscrypt_fname_usr_to_disk(inode, &istr, &ostr);
-		if (err)
-			goto err_out;
-
-		sd->len = cpu_to_le16(ostr.len);
-		disk_link.name = (char *)sd;
-	}
-
 	err = page_symlink(inode, disk_link.name, disk_link.len);
 
 err_out:
@@ -584,12 +548,14 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 		f2fs_unlink(dir, dentry);
 	}
 
-	kfree(sd);
-
 	f2fs_balance_fs(sbi, true);
-	return err;
-out:
+	goto out_free_encrypted_link;
+
+out_handle_failed_inode:
 	handle_failed_inode(inode);
+out_free_encrypted_link:
+	if (disk_link.name != (unsigned char *)symname)
+		kfree(disk_link.name);
 	return err;
 }
 
@@ -1148,68 +1114,20 @@ static const char *f2fs_encrypted_get_link(struct dentry *dentry,
 					   struct inode *inode,
 					   struct delayed_call *done)
 {
-	struct page *cpage = NULL;
-	char *caddr, *paddr = NULL;
-	struct fscrypt_str cstr = FSTR_INIT(NULL, 0);
-	struct fscrypt_str pstr = FSTR_INIT(NULL, 0);
-	struct fscrypt_symlink_data *sd;
-	u32 max_size = inode->i_sb->s_blocksize;
-	int res;
+	struct page *page;
+	const char *target;
 
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
 
-	res = fscrypt_get_encryption_info(inode);
-	if (res)
-		return ERR_PTR(res);
-
-	cpage = read_mapping_page(inode->i_mapping, 0, NULL);
-	if (IS_ERR(cpage))
-		return ERR_CAST(cpage);
-	caddr = page_address(cpage);
-
-	/* Symlink is encrypted */
-	sd = (struct fscrypt_symlink_data *)caddr;
-	cstr.name = sd->encrypted_path;
-	cstr.len = le16_to_cpu(sd->len);
-
-	/* this is broken symlink case */
-	if (unlikely(cstr.len == 0)) {
-		res = -ENOENT;
-		goto errout;
-	}
-
-	if ((cstr.len + sizeof(struct fscrypt_symlink_data) - 1) > max_size) {
-		/* Symlink data on the disk is corrupted */
-		res = -EIO;
-		goto errout;
-	}
-	res = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr);
-	if (res)
-		goto errout;
-
-	res = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
-	if (res)
-		goto errout;
-
-	/* this is broken symlink case */
-	if (unlikely(pstr.name[0] == 0)) {
-		res = -ENOENT;
-		goto errout;
-	}
-
-	paddr = pstr.name;
-
-	/* Null-terminate the name */
-	paddr[pstr.len] = '\0';
+	page = read_mapping_page(inode->i_mapping, 0, NULL);
+	if (IS_ERR(page))
+		return ERR_CAST(page);
 
-	put_page(cpage);
-	set_delayed_call(done, kfree_link, paddr);
-	return paddr;
-errout:
-	fscrypt_fname_free_buffer(&pstr);
-	put_page(cpage);
-	return ERR_PTR(res);
+	target = fscrypt_get_symlink(inode, page_address(page),
+				     inode->i_sb->s_blocksize, done);
+	put_page(page);
+	return target;
 }
 
 const struct inode_operations f2fs_encrypted_symlink_inode_operations = {

fs/ubifs/dir.c

@@ -1138,38 +1138,24 @@ static int ubifs_symlink(struct inode *dir, struct dentry *dentry,
 	struct ubifs_info *c = dir->i_sb->s_fs_info;
 	int err, len = strlen(symname);
 	int sz_change = CALC_DENT_SIZE(len);
-	struct fscrypt_str disk_link = FSTR_INIT((char *)symname, len + 1);
-	struct fscrypt_symlink_data *sd = NULL;
+	struct fscrypt_str disk_link;
 	struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1,
 					.new_ino_d = ALIGN(len, 8),
 					.dirtied_ino = 1 };
 	struct fscrypt_name nm;
 
-	if (ubifs_crypt_is_encrypted(dir)) {
-		err = fscrypt_get_encryption_info(dir);
-		if (err)
-			goto out_budg;
-
-		if (!fscrypt_has_encryption_key(dir)) {
-			err = -EPERM;
-			goto out_budg;
-		}
+	dbg_gen("dent '%pd', target '%s' in dir ino %lu", dentry,
+		symname, dir->i_ino);
 
-		disk_link.len = (fscrypt_fname_encrypted_size(dir, len) +
-				sizeof(struct fscrypt_symlink_data));
-	}
+	err = fscrypt_prepare_symlink(dir, symname, len, UBIFS_MAX_INO_DATA,
+				      &disk_link);
+	if (err)
+		return err;
 
 	/*
 	 * Budget request settings: new inode, new direntry and changing parent
 	 * directory inode.
 	 */
-
-	dbg_gen("dent '%pd', target '%s' in dir ino %lu", dentry,
-		symname, dir->i_ino);
-
-	if (disk_link.len > UBIFS_MAX_INO_DATA)
-		return -ENAMETOOLONG;
-
 	err = ubifs_budget_space(c, &req);
 	if (err)
 		return err;
@@ -1191,38 +1177,20 @@ static int ubifs_symlink(struct inode *dir, struct dentry *dentry,
 		goto out_inode;
 	}
 
-	if (ubifs_crypt_is_encrypted(dir)) {
-		struct qstr istr = QSTR_INIT(symname, len);
-		struct fscrypt_str ostr;
-
-		sd = kzalloc(disk_link.len, GFP_NOFS);
-		if (!sd) {
-			err = -ENOMEM;
-			goto out_inode;
-		}
-
-		ostr.name = sd->encrypted_path;
-		ostr.len = disk_link.len;
-
-		err = fscrypt_fname_usr_to_disk(inode, &istr, &ostr);
-		if (err) {
-			kfree(sd);
+	if (IS_ENCRYPTED(inode)) {
+		disk_link.name = ui->data; /* encrypt directly into ui->data */
+		err = fscrypt_encrypt_symlink(inode, symname, len, &disk_link);
+		if (err)
 			goto out_inode;
-		}
-
-		sd->len = cpu_to_le16(ostr.len);
-		disk_link.name = (char *)sd;
 	} else {
+		memcpy(ui->data, disk_link.name, disk_link.len);
 		inode->i_link = ui->data;
 	}
 
-	memcpy(ui->data, disk_link.name, disk_link.len);
-	((char *)ui->data)[disk_link.len - 1] = '\0';
-
 	/*
 	 * The terminating zero byte is not written to the flash media and it
 	 * is put just to make later in-memory string processing simpler. Thus,
-	 * data length is @len, not @len + %1.
+	 * data length is @disk_link.len - 1, not @disk_link.len.
 	 */
 	ui->data_len = disk_link.len - 1;
 	inode->i_size = ubifs_inode(inode)->ui_size = disk_link.len - 1;
@@ -1240,11 +1208,10 @@ static int ubifs_symlink(struct inode *dir, struct dentry *dentry,
 		goto out_cancel;
 	mutex_unlock(&dir_ui->ui_mutex);
 
-	ubifs_release_budget(c, &req);
 	insert_inode_hash(inode);
 	d_instantiate(dentry, inode);
-	fscrypt_free_filename(&nm);
-	return 0;
+	err = 0;
+	goto out_fname;
 
 out_cancel:
 	dir->i_size -= sz_change;

fs/ubifs/file.c

@@ -1629,49 +1629,17 @@ static const char *ubifs_get_link(struct dentry *dentry,
 					    struct inode *inode,
 					    struct delayed_call *done)
 {
-	int err;
-	struct fscrypt_symlink_data *sd;
 	struct ubifs_inode *ui = ubifs_inode(inode);
-	struct fscrypt_str cstr;
-	struct fscrypt_str pstr;
 
-	if (!ubifs_crypt_is_encrypted(inode))
+	if (!IS_ENCRYPTED(inode))
 		return ui->data;
 
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
 
-	err = fscrypt_get_encryption_info(inode);
-	if (err)
-		return ERR_PTR(err);
-
-	sd = (struct fscrypt_symlink_data *)ui->data;
-	cstr.name = sd->encrypted_path;
-	cstr.len = le16_to_cpu(sd->len);
-
-	if (cstr.len == 0)
-		return ERR_PTR(-ENOENT);
-
-	if ((cstr.len + sizeof(struct fscrypt_symlink_data) - 1) > ui->data_len)
-		return ERR_PTR(-EIO);
-
-	err = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr);
-	if (err)
-		return ERR_PTR(err);
-
-	err = fscrypt_fname_disk_to_usr(inode, 0, 0, &cstr, &pstr);
-	if (err) {
-		fscrypt_fname_free_buffer(&pstr);
-		return ERR_PTR(err);
-	}
-
-	pstr.name[pstr.len] = '\0';
-
-	set_delayed_call(done, kfree_link, pstr.name);
-	return pstr.name;
+	return fscrypt_get_symlink(inode, ui->data, ui->data_len, done);
 }
 
-
 const struct address_space_operations ubifs_file_address_operations = {
 	.readpage       = ubifs_readpage,
 	.writepage      = ubifs_writepage,

fs/ubifs/super.c

@@ -379,9 +379,7 @@ static void ubifs_evict_inode(struct inode *inode)
 	}
 done:
 	clear_inode(inode);
-#ifdef CONFIG_UBIFS_FS_ENCRYPTION
-	fscrypt_put_encryption_info(inode, NULL);
-#endif
+	fscrypt_put_encryption_info(inode);
 }
 
 static void ubifs_dirty_inode(struct inode *inode, int flags)

include/linux/fscrypt.h

@@ -14,42 +14,13 @@
 #ifndef _LINUX_FSCRYPT_H
 #define _LINUX_FSCRYPT_H
 
-#include <linux/key.h>
 #include <linux/fs.h>
-#include <linux/mm.h>
-#include <linux/bio.h>
-#include <linux/dcache.h>
-#include <crypto/skcipher.h>
-#include <uapi/linux/fs.h>
 
 #define FS_CRYPTO_BLOCK_SIZE		16
 
+struct fscrypt_ctx;
 struct fscrypt_info;
 
-struct fscrypt_ctx {
-	union {
-		struct {
-			struct page *bounce_page;	/* Ciphertext page */
-			struct page *control_page;	/* Original page  */
-		} w;
-		struct {
-			struct bio *bio;
-			struct work_struct work;
-		} r;
-		struct list_head free_list;	/* Free list */
-	};
-	u8 flags;				/* Flags */
-};
-
-/**
- * For encrypted symlinks, the ciphertext length is stored at the beginning
- * of the string in little-endian format.
- */
-struct fscrypt_symlink_data {
-	__le16 len;
-	char encrypted_path[1];
-} __packed;
-
 struct fscrypt_str {
 	unsigned char *name;
 	u32 len;
@@ -68,89 +39,14 @@ struct fscrypt_name {
 #define fname_name(p)		((p)->disk_name.name)
 #define fname_len(p)		((p)->disk_name.len)
 
-/*
- * fscrypt superblock flags
- */
-#define FS_CFLG_OWN_PAGES (1U << 1)
-
-/*
- * crypto opertions for filesystems
- */
-struct fscrypt_operations {
-	unsigned int flags;
-	const char *key_prefix;
-	int (*get_context)(struct inode *, void *, size_t);
-	int (*set_context)(struct inode *, const void *, size_t, void *);
-	bool (*dummy_context)(struct inode *);
-	bool (*empty_dir)(struct inode *);
-	unsigned (*max_namelen)(struct inode *);
-};
-
 /* Maximum value for the third parameter of fscrypt_operations.set_context(). */
 #define FSCRYPT_SET_CONTEXT_MAX_SIZE	28
 
-static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
-{
-	if (inode->i_sb->s_cop->dummy_context &&
-				inode->i_sb->s_cop->dummy_context(inode))
-		return true;
-	return false;
-}
-
-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)
-		return true;
-
-	if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS &&
-	    filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS)
-		return true;
-
-	return false;
-}
-
-static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
-{
-	if (str->len == 1 && str->name[0] == '.')
-		return true;
-
-	if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
-		return true;
-
-	return false;
-}
-
 #if __FS_HAS_ENCRYPTION
-
-static inline struct page *fscrypt_control_page(struct page *page)
-{
-	return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
-}
-
-static inline bool fscrypt_has_encryption_key(const struct inode *inode)
-{
-	return (inode->i_crypt_info != NULL);
-}
-
 #include <linux/fscrypt_supp.h>
-
-#else /* !__FS_HAS_ENCRYPTION */
-
-static inline struct page *fscrypt_control_page(struct page *page)
-{
-	WARN_ON_ONCE(1);
-	return ERR_PTR(-EINVAL);
-}
-
-static inline bool fscrypt_has_encryption_key(const struct inode *inode)
-{
-	return 0;
-}
-
+#else
 #include <linux/fscrypt_notsupp.h>
-#endif /* __FS_HAS_ENCRYPTION */
+#endif
 
 /**
  * fscrypt_require_key - require an inode's encryption key
@@ -291,4 +187,68 @@ static inline int fscrypt_prepare_setattr(struct dentry *dentry,
 	return 0;
 }
 
+/**
+ * fscrypt_prepare_symlink - prepare to create a possibly-encrypted symlink
+ * @dir: directory in which the symlink is being created
+ * @target: plaintext symlink target
+ * @len: length of @target excluding null terminator
+ * @max_len: space the filesystem has available to store the symlink target
+ * @disk_link: (out) the on-disk symlink target being prepared
+ *
+ * This function computes the size the symlink target will require on-disk,
+ * stores it in @disk_link->len, and validates it against @max_len.  An
+ * encrypted symlink may be longer than the original.
+ *
+ * Additionally, @disk_link->name is set to @target if the symlink will be
+ * unencrypted, but left NULL if the symlink will be encrypted.  For encrypted
+ * symlinks, the filesystem must call fscrypt_encrypt_symlink() to create the
+ * on-disk target later.  (The reason for the two-step process is that some
+ * filesystems need to know the size of the symlink target before creating the
+ * inode, e.g. to determine whether it will be a "fast" or "slow" symlink.)
+ *
+ * Return: 0 on success, -ENAMETOOLONG if the symlink target is too long,
+ * -ENOKEY if the encryption key is missing, or another -errno code if a problem
+ * occurred while setting up the encryption key.
+ */
+static inline int fscrypt_prepare_symlink(struct inode *dir,
+					  const char *target,
+					  unsigned int len,
+					  unsigned int max_len,
+					  struct fscrypt_str *disk_link)
+{
+	if (IS_ENCRYPTED(dir) || fscrypt_dummy_context_enabled(dir))
+		return __fscrypt_prepare_symlink(dir, len, max_len, disk_link);
+
+	disk_link->name = (unsigned char *)target;
+	disk_link->len = len + 1;
+	if (disk_link->len > max_len)
+		return -ENAMETOOLONG;
+	return 0;
+}
+
+/**
+ * fscrypt_encrypt_symlink - encrypt the symlink target if needed
+ * @inode: symlink inode
+ * @target: plaintext symlink target
+ * @len: length of @target excluding null terminator
+ * @disk_link: (in/out) the on-disk symlink target being prepared
+ *
+ * If the symlink target needs to be encrypted, then this function encrypts it
+ * into @disk_link->name.  fscrypt_prepare_symlink() must have been called
+ * previously to compute @disk_link->len.  If the filesystem did not allocate a
+ * buffer for @disk_link->name after calling fscrypt_prepare_link(), then one
+ * will be kmalloc()'ed and the filesystem will be responsible for freeing it.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+static inline int fscrypt_encrypt_symlink(struct inode *inode,
+					  const char *target,
+					  unsigned int len,
+					  struct fscrypt_str *disk_link)
+{
+	if (IS_ENCRYPTED(inode))
+		return __fscrypt_encrypt_symlink(inode, target, len, disk_link);
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_H */

include/linux/fscrypt_notsupp.h

@@ -14,6 +14,16 @@
 #ifndef _LINUX_FSCRYPT_NOTSUPP_H
 #define _LINUX_FSCRYPT_NOTSUPP_H
 
+static inline bool fscrypt_has_encryption_key(const struct inode *inode)
+{
+	return false;
+}
+
+static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
+{
+	return false;
+}
+
 /* crypto.c */
 static inline struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode,
 						  gfp_t gfp_flags)
@@ -43,6 +53,11 @@ static inline int fscrypt_decrypt_page(const struct inode *inode,
 	return -EOPNOTSUPP;
 }
 
+static inline struct page *fscrypt_control_page(struct page *page)
+{
+	WARN_ON_ONCE(1);
+	return ERR_PTR(-EINVAL);
+}
 
 static inline void fscrypt_restore_control_page(struct page *page)
 {
@@ -90,8 +105,7 @@ static inline int fscrypt_get_encryption_info(struct inode *inode)
 	return -EOPNOTSUPP;
 }
 
-static inline void fscrypt_put_encryption_info(struct inode *inode,
-					       struct fscrypt_info *ci)
+static inline void fscrypt_put_encryption_info(struct inode *inode)
 {
 	return;
 }
@@ -116,16 +130,8 @@ static inline void fscrypt_free_filename(struct fscrypt_name *fname)
 	return;
 }
 
-static inline u32 fscrypt_fname_encrypted_size(const struct inode *inode,
-					       u32 ilen)
-{
-	/* never happens */
-	WARN_ON(1);
-	return 0;
-}
-
 static inline int fscrypt_fname_alloc_buffer(const struct inode *inode,
-					     u32 ilen,
+					     u32 max_encrypted_len,
 					     struct fscrypt_str *crypto_str)
 {
 	return -EOPNOTSUPP;
@@ -144,13 +150,6 @@ static inline int fscrypt_fname_disk_to_usr(struct inode *inode,
 	return -EOPNOTSUPP;
 }
 
-static inline int fscrypt_fname_usr_to_disk(struct inode *inode,
-					    const struct qstr *iname,
-					    struct fscrypt_str *oname)
-{
-	return -EOPNOTSUPP;
-}
-
 static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
 				      const u8 *de_name, u32 de_name_len)
 {
@@ -208,4 +207,28 @@ static inline int __fscrypt_prepare_lookup(struct inode *dir,
 	return -EOPNOTSUPP;
 }
 
+static inline int __fscrypt_prepare_symlink(struct inode *dir,
+					    unsigned int len,
+					    unsigned int max_len,
+					    struct fscrypt_str *disk_link)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int __fscrypt_encrypt_symlink(struct inode *inode,
+					    const char *target,
+					    unsigned int len,
+					    struct fscrypt_str *disk_link)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline const char *fscrypt_get_symlink(struct inode *inode,
+					      const void *caddr,
+					      unsigned int max_size,
+					      struct delayed_call *done)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

include/linux/fscrypt_supp.h

@@ -11,8 +11,54 @@
 #ifndef _LINUX_FSCRYPT_SUPP_H
 #define _LINUX_FSCRYPT_SUPP_H
 
+#include <linux/mm.h>
+#include <linux/slab.h>
+
+/*
+ * fscrypt superblock flags
+ */
+#define FS_CFLG_OWN_PAGES (1U << 1)
+
+/*
+ * crypto operations for filesystems
+ */
+struct fscrypt_operations {
+	unsigned int flags;
+	const char *key_prefix;
+	int (*get_context)(struct inode *, void *, size_t);
+	int (*set_context)(struct inode *, const void *, size_t, void *);
+	bool (*dummy_context)(struct inode *);
+	bool (*empty_dir)(struct inode *);
+	unsigned (*max_namelen)(struct inode *);
+};
+
+struct fscrypt_ctx {
+	union {
+		struct {
+			struct page *bounce_page;	/* Ciphertext page */
+			struct page *control_page;	/* Original page  */
+		} w;
+		struct {
+			struct bio *bio;
+			struct work_struct work;
+		} r;
+		struct list_head free_list;	/* Free list */
+	};
+	u8 flags;				/* Flags */
+};
+
+static inline bool fscrypt_has_encryption_key(const struct inode *inode)
+{
+	return (inode->i_crypt_info != NULL);
+}
+
+static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
+{
+	return inode->i_sb->s_cop->dummy_context &&
+		inode->i_sb->s_cop->dummy_context(inode);
+}
+
 /* crypto.c */
-extern struct kmem_cache *fscrypt_info_cachep;
 extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
 extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
@@ -20,6 +66,12 @@ extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
 						u64, gfp_t);
 extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
 				unsigned int, u64);
+
+static inline struct page *fscrypt_control_page(struct page *page)
+{
+	return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
+}
+
 extern void fscrypt_restore_control_page(struct page *);
 
 extern const struct dentry_operations fscrypt_d_ops;
@@ -44,7 +96,7 @@ extern int fscrypt_inherit_context(struct inode *, struct inode *,
 					void *, bool);
 /* keyinfo.c */
 extern int fscrypt_get_encryption_info(struct inode *);
-extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *);
+extern void fscrypt_put_encryption_info(struct inode *);
 
 /* fname.c */
 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
@@ -55,14 +107,11 @@ static inline void fscrypt_free_filename(struct fscrypt_name *fname)
 	kfree(fname->crypto_buf.name);
 }
 
-extern u32 fscrypt_fname_encrypted_size(const struct inode *, u32);
 extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
 				struct fscrypt_str *);
 extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
 extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
 			const struct fscrypt_str *, struct fscrypt_str *);
-extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
-			struct fscrypt_str *);
 
 #define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE	32
 
@@ -153,5 +202,14 @@ extern int __fscrypt_prepare_rename(struct inode *old_dir,
 				    struct dentry *new_dentry,
 				    unsigned int flags);
 extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry);
+extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
+				     unsigned int max_len,
+				     struct fscrypt_str *disk_link);
+extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
+				     unsigned int len,
+				     struct fscrypt_str *disk_link);
+extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
+				       unsigned int max_size,
+				       struct delayed_call *done);
 
 #endif	/* _LINUX_FSCRYPT_SUPP_H */