linux-kernel - Re: general protection fault in finish_task

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Message-ID: <CACT4Y+ZKkUGzfgL5K-aLz8+VcFcFF1bWHR3LDRvCO-DtXhD8Ww@mail.gmail.com>
Date:   Fri, 24 Aug 2018 13:16:08 -0700
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     syzbot <syzbot+1f56df64bfb3c29dde6f@...kaller.appspotmail.com>,
        Darren Hart <dvhart@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, KVM list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: general protection fault in finish_task_switch (2)

On Wed, Aug 22, 2018 at 2:08 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, Aug 21, 2018 at 02:28:02PM -0700, syzbot wrote:
>> syzbot has found a reproducer for the following crash on:
>>
>> HEAD commit:    778a33959a8a Merge tag 'please-pull-noboot' of git://git.k..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=14a5385a400000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=214e4990bd49329f
>> dashboard link: https://syzkaller.appspot.com/bug?extid=1f56df64bfb3c29dde6f
>> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>> userspace arch: i386
>> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=13ffa561400000
>
> FWIW the lack of whitespace between "repro:" and the URL makes it hard
> to copy paste.

Fixed by:
https://github.com/google/syzkaller/commit/307deaee5e23e4585d4b408ebcf329b9dc8ebdb4
Thanks

>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10023961400000
>
>
>> RIP: 0010:__fire_sched_in_preempt_notifiers kernel/sched/core.c:2481
>
> That repro thing does something dodgy with KVM, which then corrupts the
> premption notifier thing. I'm sufficiently KVM clueless to not really
> know where to start looking though..