2024-04-14 00:34:54

by Danny Lin

Subject: [PATCH] fuse: fix leaked ENOSYS error on first statx call

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: [email protected] # v6.6
Signed-off-by: Danny Lin <[email protected]>
---
fs/fuse/dir.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index de452cdbf3cf..a63125ce70a4 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1362,6 +1362,7 @@ static int fuse_update_get_attr(struct inode *inode, struct file *file,
err = fuse_do_statx(inode, file, stat);
if (err == -ENOSYS) {
fc->no_statx = 1;
+ err = 0;
goto retry;
}
} else {
--
2.44.0

2024-04-15 08:00:32

by Miklos Szeredi

Subject: Re: [PATCH] fuse: fix leaked ENOSYS error on first statx call

On Sun, 14 Apr 2024 at 02:34, Danny Lin <[email protected]> wrote:
>
> 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.

Thanks, applied.

Miklos