Re: [syzbot] WARNING in io_wqe_enqueue

[Hao Xu]

在 2021/6/8 下午8:01, Dmitry Vyukov 写道:
> On Tue, Jun 8, 2021 at 11:47 AM Hao Xu <haoxu@xxxxxxxxxxxxxxxxx> wrote:
> > 在 2021/6/5 上午4:22, syzbot 写道:
> > > syzbot has bisected this issue to:
> > >
> > > commit 24369c2e3bb06d8c4e71fd6ceaf4f8a01ae79b7c
> > > Author: Pavel Begunkov <asml.silence@xxxxxxxxx>
> > > Date:   Tue Jan 28 00:15:48 2020 +0000
> > >
> > >       io_uring: add io-wq workqueue sharing
> > >
> > > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17934777d00000
> > > start commit:   f88cd3fb Merge tag 'vfio-v5.13-rc5' of git://github.com/aw..
> > > git tree:       upstream
> > > final oops:     https://syzkaller.appspot.com/x/report.txt?x=14534777d00000
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=10534777d00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=82d85e75046e5e64
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=ea2f1484cffe5109dc10
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16d5772fd00000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10525947d00000
> > >
> > > Reported-by: syzbot+ea2f1484cffe5109dc10@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Fixes: 24369c2e3bb0 ("io_uring: add io-wq workqueue sharing")
> > >
> > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> > This is not a bug, the repro program first set RLIMIT_NPROC to 0, then
> > submits an unbound work whcih raises a warning of
> > WARN_ON_ONCE(!acct->max_workers). Since unbound->max_workers is
> > task_rlimit(current, RLIMIT_NPROC), so it is expected.
>
> Hi Hao,
>
> Then this is a mis-use of WARN_ON. If this check is intended for end
> users, it needs to use pr_err (also print understandable message and
> no stack trace which is most likely not useful for end users):
> https://elixir.bootlin.com/linux/v5.13-rc5/source/include/asm-generic/bug.h#L71
 Agree, pr_err/pr_warn is better here.