linux-kernel - Re: INFO: task hung in locks_remove

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Message-ID: <CACT4Y+bAg0jJSVSu-AwP2k5QMk3kgnwRn4xXb3C5Mx-CyMRwdA@mail.gmail.com>
Date:   Thu, 21 May 2020 16:21:06 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     syzbot <syzbot+f5bc30abd8916982419c@...kaller.appspotmail.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: INFO: task hung in locks_remove_posix

On Thu, May 21, 2020 at 4:09 PM Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
>
> On 2020/05/21 5:53, syzbot wrote:
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    806d8acc USB: dummy-hcd: use configurable endpoint naming ..
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16c9ece2100000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=d800e9bad158025f
> > dashboard link: https://syzkaller.appspot.com/bug?extid=f5bc30abd8916982419c
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> >
> > Unfortunately, I don't have any reproducer for this crash yet.
>
> This seems to be a mislabeling due to '?' in all lines in a trace.
>
> #syz dup: INFO: task hung in wdm_flush

It seems that unwind from __schedule is broken. Fixing the unwinder
may be the action item here, otherwise we will get an infinite number
of such reports.