fscrypt: use ENOKEY when file cannot be created w/o key

As part of an effort to clean up fscrypt-related error codes, make
attempting to create a file in an encrypted directory that hasn't been
"unlocked" fail with ENOKEY.  Previously, several error codes were used
for this case, including ENOENT, EACCES, and EPERM, and they were not
consistent between and within filesystems.  ENOKEY is a better choice
because it expresses that the failure is due to lacking the encryption
key.  It also matches the error code returned when trying to open an
encrypted regular file without the key.

I am not aware of any users who might be relying on the previous
inconsistent error codes, which were never documented anywhere.

This failure case will be exercised by an xfstest.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/crypto/fname.c

@@ -332,7 +332,7 @@ int fscrypt_fname_usr_to_disk(struct inode *inode,
 	 * in a directory. Consequently, a user space name cannot be mapped to
 	 * a disk-space name
 	 */
-	return -EACCES;
+	return -ENOKEY;
 }
 EXPORT_SYMBOL(fscrypt_fname_usr_to_disk);
 
@@ -367,7 +367,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 		return 0;
 	}
 	if (!lookup)
-		return -EACCES;
+		return -ENOKEY;
 
 	/*
 	 * We don't have the key and we are doing a lookup; decode the

fs/ext4/ialloc.c

@@ -771,7 +771,7 @@ struct inode *__ext4_new_inode(handle_t *handle, struct inode *dir,
 		if (err)
 			return ERR_PTR(err);
 		if (!fscrypt_has_encryption_key(dir))
-			return ERR_PTR(-EPERM);
+			return ERR_PTR(-ENOKEY);
 		if (!handle)
 			nblocks += EXT4_DATA_TRANS_BLOCKS(dir->i_sb);
 		encrypt = 1;

fs/ext4/namei.c

@@ -1378,6 +1378,8 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
 		return NULL;
 
 	retval = ext4_fname_setup_filename(dir, d_name, 1, &fname);
+	if (retval == -ENOENT)
+		return NULL;
 	if (retval)
 		return ERR_PTR(retval);
 
@@ -3088,7 +3090,7 @@ static int ext4_symlink(struct inode *dir,
 		if (err)
 			return err;
 		if (!fscrypt_has_encryption_key(dir))
-			return -EPERM;
+			return -ENOKEY;
 		disk_link.len = (fscrypt_fname_encrypted_size(dir, len) +
 				 sizeof(struct fscrypt_symlink_data));
 		sd = kzalloc(disk_link.len, GFP_KERNEL);

fs/f2fs/dir.c

@@ -268,6 +268,9 @@ struct f2fs_dir_entry *f2fs_find_entry(struct inode *dir,
 
 	err = fscrypt_setup_filename(dir, child, 1, &fname);
 	if (err) {
+		if (err == -ENOENT)
+			*res_page = NULL;
+		else
 			*res_page = ERR_PTR(err);
 		return NULL;
 	}

fs/f2fs/namei.c

@@ -403,7 +403,7 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 			return err;
 
 		if (!fscrypt_has_encryption_key(dir))
-			return -EPERM;
+			return -ENOKEY;
 
 		disk_link.len = (fscrypt_fname_encrypted_size(dir, len) +
 				sizeof(struct fscrypt_symlink_data));
@@ -447,7 +447,7 @@ static int f2fs_symlink(struct inode *dir, struct dentry *dentry,
 			goto err_out;
 
 		if (!fscrypt_has_encryption_key(inode)) {
-			err = -EPERM;
+			err = -ENOKEY;
 			goto err_out;
 		}