statx: Kill fd-with-NULL-path support in favour of AT_EMPTY_PATH
With the new statx() syscall, the following both allow the attributes of
the file attached to a file descriptor to be retrieved:
statx(dfd, NULL, 0, ...);
and:
statx(dfd, "", AT_EMPTY_PATH, ...);
Change the code to reject the first option, though this means copying
the path and engaging pathwalk for the fstat() equivalent. dfd can be a
non-directory provided path is "".
[ The timing of this isn't wonderful, but applying this now before we
have statx() in any released kernel, before anybody starts using the
NULL special case. - Linus ]
Fixes: a528d35e8bfc ("statx: Add a system call to make enhanced file info available")
Reported-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Eric Sandeen <sandeen@sandeen.net>
cc: fstests@vger.kernel.org
cc: linux-api@vger.kernel.org
cc: linux-man@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/stat.c b/fs/stat.c
index c6c963b..3d85747 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -547,13 +547,13 @@
/**
* sys_statx - System call to get enhanced stats
* @dfd: Base directory to pathwalk from *or* fd to stat.
- * @filename: File to stat *or* NULL.
+ * @filename: File to stat or "" with AT_EMPTY_PATH
* @flags: AT_* flags to control pathwalk.
* @mask: Parts of statx struct actually required.
* @buffer: Result buffer.
*
- * Note that if filename is NULL, then it does the equivalent of fstat() using
- * dfd to indicate the file of interest.
+ * Note that fstat() can be emulated by setting dfd to the fd of interest,
+ * supplying "" as the filename and setting AT_EMPTY_PATH in the flags.
*/
SYSCALL_DEFINE5(statx,
int, dfd, const char __user *, filename, unsigned, flags,
@@ -567,11 +567,10 @@
return -EINVAL;
if ((flags & AT_STATX_SYNC_TYPE) == AT_STATX_SYNC_TYPE)
return -EINVAL;
+ if (!filename)
+ return -EINVAL;
- if (filename)
- error = vfs_statx(dfd, filename, flags, &stat, mask);
- else
- error = vfs_statx_fd(dfd, &stat, mask, flags);
+ error = vfs_statx(dfd, filename, flags, &stat, mask);
if (error)
return error;
