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From: Dmitry Vyukov <dvyukov@google.com>
Date: Mon, 20 Nov 2017 14:28:18 +0100
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Subject: Re: general protection fault in lockdep_invariant_state (2)
To: Peter Zijlstra <peterz@infradead.org>
Cc: syzbot 
        <bot+2e39c7a45268c036c9e90433a48c9dd550276dc6@syzkaller.appspotmail.com>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@redhat.com>,
        syzkaller-bugs@googlegroups.com
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On Wed, Nov 8, 2017 at 9:40 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Nov 08, 2017 at 09:19:53AM +0100, Dmitry Vyukov wrote:
>
>> > R13: 0000000000402260 R14: 00000000004022f0 R15: 0000000000000000
>> > kasan: CONFIG_KASAN_INLINE enabled
>> > kasan: GPF could be caused by NULL-ptr deref or user memory access
>> > general protection fault: 0000 [#1] SMP KASAN
>> > Dumping ftrace buffer:
>> >    (ftrace buffer empty)
>> > Modules linked in:
>> > CPU: 3 PID: 2982 Comm: syzkaller521009 Not tainted 4.14.0-rc7-next-20171103+
>> > #10
>> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>> > task: ffff88003d6b25c0 task.stack: ffff88003abd0000
>> > RIP: 0010:invalidate_xhlock kernel/locking/lockdep.c:4719 [inline]
>> > RIP: 0010:lockdep_invariant_state+0xd6/0x120 kernel/locking/lockdep.c:4793
>
>
> Does this help?
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index db933d063bfc..da2904418599 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -4793,7 +4793,8 @@ void lockdep_invariant_state(bool force)
>          * Verify the former, enforce the latter.
>          */
>         WARN_ON_ONCE(!force && current->lockdep_depth);
> -       invalidate_xhlock(&xhlock(current->xhlock_idx));
> +       if (current->xhlocks)
> +               invalidate_xhlock(&xhlock(current->xhlock_idx));
>  }
>
>  static int cross_lock(struct lockdep_map *lock)


Hi Peter,

We are not able to test all fixes for all bugs, but we are rolling out
a patch testing feature for syzbot:

https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot

Please give it a try!