From 1e2f82d1e9d12223b4cbd1feb3f2b5596f8049eb Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 26 Apr 2017 22:15:55 +0100 Subject: [PATCH] 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 Signed-off-by: David Howells cc: Eric Sandeen cc: fstests@vger.kernel.org cc: linux-api@vger.kernel.org cc: linux-man@vger.kernel.org Signed-off-by: Linus Torvalds --- fs/stat.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/stat.c b/fs/stat.c index c6c963b2546b..3d85747bd86e 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -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); + error = vfs_statx(dfd, filename, flags, &stat, mask); if (error) return error;