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

On Sun, 14 Apr 2024 at 02:34, Danny Lin danny@orbstack.dev 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