statx: correct error handling of NULL pathname

The change in commit 1e2f82d1e9d1 ("statx: Kill fd-with-NULL-path
support in favour of AT_EMPTY_PATH") to error on a NULL pathname to
statx() is inconsistent.

It results in the error EINVAL for a NULL pathname.  Other system calls
with similar APIs (fchownat(), fstatat(), linkat()), return EFAULT.

The solution is simply to remove the EINVAL check.  As I already pointed
out in [1], user_path_at*() and filename_lookup() will handle the NULL
pathname as per the other APIs, to correctly produce the error EFAULT.

[1] https://lkml.org/lkml/2017/4/26/561

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/stat.c b/fs/stat.c
index 3d85747..a257b87 100644 (file)
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -567,8 +567,6 @@ SYSCALL_DEFINE5(statx,
                return -EINVAL;
        if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
                return -EINVAL;
-       if (!filename)
-               return -EINVAL;
 
        error = vfs_statx(dfd, filename, flags, &stat, mask);
        if (error)