On Wed, 24 Nov 2021 19:47:40 +0900, Tetsuo Handa wrote:
> syzbot is reporting circular locking problem at __loop_clr_fd() [1], for
> commit 87579e9b7d8dc36e ("loop: use worker per cgroup instead of kworker")
> is calling destroy_workqueue() with lo->lo_mutex held.
>
> Since all functions where lo->lo_state matters are already checking
> lo->lo_state with lo->lo_mutex held (in order to avoid racing with e.g.
> ioctl(LOOP_CTL_REMOVE)), and __loop_clr_fd() can be called from either
> ioctl(LOOP_CLR_FD) xor close(), lo->lo_state == Lo_rundown is considered
> as an exclusive lock for __loop_clr_fd(). Therefore, hold lo->lo_mutex
> inside __loop_clr_fd() only when asserting/updating lo->lo_state.
>
> [...]
Applied, thanks!
[1/1] loop: don't hold lo_mutex during __loop_clr_fd()
commit: c895b784c699224d690c7dfbdcff309df82366e3
Best regards,
--
Jens Axboe
