[PATCH 6.6 140/158] fuse: fix leaked ENOSYS error on first statx call

Greg Kroah-Hartman
2024-04-23T21:44:11Z

From: Danny Lin <danny@orbstack.dev>

commit eb4b691b9115fae4c844f5941418335575cf667f upstream.

FUSE attempts to detect server support for statx by trying it once and
setting no_statx=1 if it fails with ENOSYS, but consider the following
scenario:

- Userspace (e.g. sh) calls stat() on a file
* succeeds
- Userspace (e.g. lsd) calls statx(BTIME) on the same file
- request_mask = STATX_BASIC_STATS | STATX_BTIME
- first pass: sync=true due to differing cache_mask
- statx fails and returns ENOSYS
- set no_statx and retry
- retry sets mask = STATX_BASIC_STATS
- now mask == cache_mask; sync=false (time_before: still valid)
- so we take the "else if (stat)" path
- "err" is still ENOSYS from the failed statx call

Fix this by zeroing "err" before retrying the failed call.

Fixes: d3045530bdd2 ("fuse: implement statx")
Cc: stable@vger.kernel.org # v6.6
Signed-off-by: Danny Lin <danny@orbstack.dev>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/fuse/dir.c | 1 +
1 file changed, 1 insertion(+)

--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1317,6 +1317,7 @@ retry:
err = fuse_do_statx(inode, file, stat);
if (err == -ENOSYS) {
fc->no_statx = 1;
+ err = 0;
goto retry;
}
} else {