statx: Kill fd-with-NULL-path support in favour of AT_EMPTY_PATH (1e2f82d1) · Commits · 戴 / test

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: ("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>

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;

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