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Commit 1e2f82d1 authored by David Howells's avatar David Howells Committed by Linus Torvalds
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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: a528d35e ("statx: Add a system call to make enhanced file info available")
Reported-by: default avatarMichael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: default avatarDavid 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fc08b197

fs/stat.c

+6 −7
Original line number Diff line number Diff line
@@ -547,13 +547,13 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) 
/**

 * 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 @@ SYSCALL_DEFINE5(statx, 
		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);

	if (error)

		return error;