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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 12 Mar 2019 17:09:38 +0100
Message-ID: <CACT4Y+ZoDc=_a_W=wVMYj+VLW8WFBDbQJGB17dZTSvYinWhebA@mail.gmail.com>
Subject: Re: WARNING in hsr_forward_skb
To:     Oliver Hartkopp <socketcan@hartkopp.net>
Cc:     syzbot <syzbot+fdce8f2a8903f3ba0e6b@syzkaller.appspotmail.com>,
        arvid.brodin@alten.se, Jens Axboe <axboe@fb.com>,
        Jens Axboe <axboe@kernel.dk>,
        David Miller <davem@davemloft.net>,
        Christoph Hellwig <hch@lst.de>, linux-block@vger.kernel.org,
        linux-can@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        Ming Lei <ming.lei@redhat.com>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        netdev <netdev@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Tue, Mar 12, 2019 at 1:02 PM Oliver Hartkopp <socketcan@hartkopp.net> wrote:
>
> Hi all,
>
> I'm not sure why a Kernel 4.12.0-rc2+ is used here, but I do not get any
> problems on the my latest 5.0.0-06622-g1fc1cd8399ab tree and I strongly
> assume this patch showing up in 4.12-rc6
>
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit?id=74b7b490886852582d986a33443c2ffa50970169
>
> fixes the problem.


Hi Oliver,

You can see how bisection progressed and got to 4.12.0-rc2+ in the
bisection log.

The commit that it come up with looks unrelated.
I've started collecting such cases at:
https://github.com/google/syzkaller/issues/1051
and added for this case:

=====
Bisected to wrong commit.
Root cause: broken kernel boots, bugs that happen on all tests.
Boot is broken for several releases with "WARNING in hsr_forward_skb",
this switches to a bug that happens during every test "INFO: trying to
register non-static key in can_notifier", which then leads to a
completely random commit.
=====


> On 3/12/19 9:57 AM, syzbot wrote:
> > syzbot has bisected this bug to:
> >
> > commit ab42f35d9cb5ac49b5a2a11f940e74f58f207280
> > Author: Ming Lei <ming.lei@redhat.com>
> > Date:   Fri May 26 11:53:19 2017 +0000
> >
> >      blk-mq: merge bio into sw queue before plugging
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16e68713200000
> > start commit:   ab42f35d blk-mq: merge bio into sw queue before plugging
> > git tree:       upstream
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=15e68713200000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=11e68713200000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=5e7dc790609552d7
> > dashboard link:
> > https://syzkaller.appspot.com/bug?extid=fdce8f2a8903f3ba0e6b
> > userspace arch: amd64
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15f6d1fd400000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17290fdd400000
> >
> > Reported-by: syzbot+fdce8f2a8903f3ba0e6b@syzkaller.appspotmail.com
> > Fixes: ab42f35d ("blk-mq: merge bio into sw queue before plugging")
>
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