Re: WARNING in hsr_forward_skb

From: Dmitry Vyukov <dvyukov@google.com>
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>
Subject: Re: WARNING in hsr_forward_skb
Date: Tue, 12 Mar 2019 17:21:24 +0100	[thread overview]
Message-ID: <CACT4Y+ayyFe6oek8MdnUd1LsB_+1kpJatBLnmF_jCttQPyCK0g@mail.gmail.com> (raw)
In-Reply-To: <CACT4Y+ZoDc=_a_W=wVMYj+VLW8WFBDbQJGB17dZTSvYinWhebA@mail.gmail.com>

On Tue, Mar 12, 2019 at 5:09 PM Dmitry Vyukov <dvyukov@google.com> wrote:
>
> 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.
> =====

Broken boots did not happen here. "WARNING in hsr_forward_skb" is the
crash that we pursued, so it started correctly. But then diverged to
an unrelated "INFO: trying to register non-static key in
can_notifier".

> > 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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