fscrypto: lock inode while setting encryption policy

i_rwsem needs to be acquired while setting an encryption policy so that
concurrent calls to FS_IOC_SET_ENCRYPTION_POLICY are correctly
serialized (especially the ->get_context() + ->set_context() pair), and
so that new files cannot be created in the directory during or after the
->empty_dir() check.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Richard Weinberger <richard@nod.at>
Cc: stable@vger.kernel.org

diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
index ed115ac..6865663 100644 (file)
--- a/fs/crypto/policy.c
+++ b/fs/crypto/policy.c
@@ -109,6 +109,8 @@ int fscrypt_process_policy(struct file *filp,
        if (ret)
                return ret;
 
+       inode_lock(inode);
+
        if (!inode_has_encryption_context(inode)) {
                if (!S_ISDIR(inode->i_mode))
                        ret = -EINVAL;
@@ -127,6 +129,8 @@ int fscrypt_process_policy(struct file *filp,
                ret = -EINVAL;
        }
 
+       inode_unlock(inode);
+
        mnt_drop_write_file(filp);
        return ret;
 }