On Thu, 3 Sep 2020 19:10:11 -0700 Cong Wang wrote:
> The following deadlock scenario is triggered by syzbot:
>
> Thread A: Thread B:
> tcf_idr_check_alloc()
> ...
> populate_metalist()
> rtnl_unlock()
> rtnl_lock()
> ...
> request_module() tcf_idr_check_alloc()
> rtnl_lock()
>
> At this point, thread A is waiting for thread B to release RTNL
> lock, while thread B is waiting for thread A to commit the IDR
> change with tcf_idr_insert() later.
>
> Break this deadlock situation by preloading ife modules earlier,
> before tcf_idr_check_alloc(), this is fine because we only need
> to load modules we need potentially.
>
> Reported-and-tested-by: syzbot+80e32b5d1f9923f8a...@syzkaller.appspotmail.com
> Fixes: 0190c1d452a9 ("net: sched: atomically check-allocate action")
> Cc: Jamal Hadi Salim <j...@mojatatu.com>
> Cc: Vlad Buslov <vla...@mellanox.com>
Vlad, it'd have been nice to see your review tag here.
> Cc: Jiri Pirko <j...@resnulli.us>
> Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
LGTM, applied and queued for stable, thank you Cong!
