fs/mount_setattr: always cleanup mount_kattr

Make sure that finish_mount_kattr() is called after mount_kattr was
succesfully built in both the success and failure case to prevent
leaking any references we took when we built it.  We returned early if
path lookup failed thereby risking to leak an additional reference we
took when building mount_kattr when an idmapped mount was requested.

Cc: [email protected]
Cc: [email protected]
Fixes: 9caccd4 ("fs: introduce MOUNT_ATTR_IDMAP")
Signed-off-by: Christian Brauner <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Christian Brauner

fs/namespace.c

@@ -4263,12 +4263,11 @@ SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
 		return err;
 
 	err = user_path_at(dfd, path, kattr.lookup_flags, &target);
-	if (err)
-		return err;
-
-	err = do_mount_setattr(&target, &kattr);
+	if (!err) {
+		err = do_mount_setattr(&target, &kattr);
+		path_put(&target);
+	}
 	finish_mount_kattr(&kattr);
-	path_put(&target);
 	return err;
 }