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authorEric Biggers <ebiggers@google.com>2017-10-09 12:15:42 -0700
committerTheodore Ts'o <tytso@mit.edu>2017-10-18 19:52:38 -0400
commit94b26f3672a0e41025104c7e46943917544e1c87 (patch)
tree89c19235e098d8f71662a23992c1800a8681b44f /include/linux/fscrypt.h
parent0ea87a9644ebb5c9a3b100585d10533366de3269 (diff)
fscrypt: new helper function - fscrypt_prepare_rename()
Introduce a helper function which prepares to rename a file into a possibly encrypted directory. It handles loading the encryption keys for the source and target directories if needed, and it handles enforcing that if the target directory (and the source directory for a cross-rename) is encrypted, then the file being moved into the directory has the same encryption policy as its containing directory. Acked-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'include/linux/fscrypt.h')
-rw-r--r--include/linux/fscrypt.h33
1 files changed, 33 insertions, 0 deletions
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 9c9a53f99327..c422367baed9 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -204,4 +204,37 @@ static inline int fscrypt_prepare_link(struct dentry *old_dentry,
return 0;
}
+/**
+ * fscrypt_prepare_rename - prepare for a rename between possibly-encrypted directories
+ * @old_dir: source directory
+ * @old_dentry: dentry for source file
+ * @new_dir: target directory
+ * @new_dentry: dentry for target location (may be negative unless exchanging)
+ * @flags: rename flags (we care at least about %RENAME_EXCHANGE)
+ *
+ * Prepare for ->rename() where the source and/or target directories may be
+ * encrypted. A new link can only be added to an encrypted directory if the
+ * directory's encryption key is available --- since otherwise we'd have no way
+ * to encrypt the filename. A rename to an existing name, on the other hand,
+ * *is* cryptographically possible without the key. However, we take the more
+ * conservative approach and just forbid all no-key renames.
+ *
+ * We also verify that the rename will not violate the constraint that all files
+ * in an encrypted directory tree use the same encryption policy.
+ *
+ * Return: 0 on success, -ENOKEY if an encryption key is missing, -EPERM if the
+ * rename would cause inconsistent encryption policies, or another -errno code.
+ */
+static inline int fscrypt_prepare_rename(struct inode *old_dir,
+ struct dentry *old_dentry,
+ struct inode *new_dir,
+ struct dentry *new_dentry,
+ unsigned int flags)
+{
+ if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir))
+ return __fscrypt_prepare_rename(old_dir, old_dentry,
+ new_dir, new_dentry, flags);
+ return 0;
+}
+
#endif /* _LINUX_FSCRYPT_H */