[!] NOTE: This breaks UAPI introduced in 4.11-rc1.
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 "".
Fixes: a528d35e8bfc ("statx: Add a system call to make enhanced file info available")
Reported-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Eric Sandeen <sandeen@xxxxxxxxxxx>
cc: fstests@xxxxxxxxxxxxxxx
cc: linux-api@xxxxxxxxxxxxxxx
cc: linux-man@xxxxxxxxxxxxxxx
---
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;
--
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