Re: INFO: trying to register non-static key in try_to_wake_up

[Bartlomiej Zolnierkiewicz]

On 3/31/20 12:18 PM, Dmitry Vyukov wrote:
> On Tue, Mar 31, 2020 at 11:57 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>>
>> On Mon, Mar 30, 2020 at 10:01:12PM -0700, syzbot wrote:
>>> Hello,
>>>
>>> syzbot found the following crash on:
>>>
>>> HEAD commit:    9420e8ad Merge tag 'for-linus' of git://git.kernel.org/pub..
>>> git tree:       upstream
>>> console output: https://protect2.fireeye.com/url?k=0756a78d-5a9a6c49-07572cc2-0cc47a314e9a-e4dc8b657d340686&u=https://syzkaller.appspot.com/x/log.txt?x=1206ed4be00000
>>> kernel config:  https://protect2.fireeye.com/url?k=43211072-1eeddbb6-43209b3d-0cc47a314e9a-3bd45a19932c37c8&u=https://syzkaller.appspot.com/x/.config?x=27392dd2975fd692
>>> dashboard link: https://protect2.fireeye.com/url?k=bf7a6153-e2b6aa97-bf7bea1c-0cc47a314e9a-c64073ee605efb7b&u=https://syzkaller.appspot.com/bug?extid=e84d7ebd1361da13c356
>>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>>>
>>> Unfortunately, I don't have any reproducer for this crash yet.
>>>
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by: syzbot+e84d7ebd1361da13c356@xxxxxxxxxxxxxxxxxxxxxxxxx
>>>
>>> INFO: trying to register non-static key.
>>> the code is fine but needs lockdep annotation.
>>> turning off the locking correctness validator.
>>> CPU: 1 PID: 1014 Comm: syz-executor.0 Not tainted 5.6.0-rc7-syzkaller #0
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>>> Call Trace:
>>>  <IRQ>
>>>  __dump_stack lib/dump_stack.c:77 [inline]
>>>  dump_stack+0x188/0x20d lib/dump_stack.c:118
>>>  assign_lock_key kernel/locking/lockdep.c:880 [inline]
>>>  register_lock_class+0x14c4/0x1540 kernel/locking/lockdep.c:1189
>>>  __lock_acquire+0xfc/0x3ca0 kernel/locking/lockdep.c:3836
>>>  lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4484
>>>  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>>>  _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>>>  try_to_wake_up+0x9f/0x17c0 kernel/sched/core.c:2547
>>
>> That's p->pi_lock, which gets initialized in rt_mutex_init_task() in
>> copy_process(). This should be impossible. Very odd.
> 
> The stack mentions fbdev, which is a red flag at the moment. There are
> a dozen of bad bugs in fbdev and around. Just few days ago Andy
> pointed to another "impossible" crash "general protection fault in
> do_syscall_64" which is related to dri:
> https://protect2.fireeye.com/url?k=0cb8ad06-517466c2-0cb92649-0cc47a314e9a-a20c11191483c65b&u=https://syzkaller.appspot.com/bug?id=0ec7b2602b1ff40f0d34f38baa4ba1640727c3d9
> https://protect2.fireeye.com/url?k=614292e3-3c8e5927-614319ac-0cc47a314e9a-aeda6d72c01a7b0e&u=https://groups.google.com/forum/#!msg/syzkaller-bugs/ePqhfYx0-8M/Q_Urt97iAAAJ
> 
> There are probably more random manifestations of these bugs already,
> and I guess we will be getting more.
> 
> +fbdev maintainers

Thank you for the report.

fbdev is in the maintenance mode and no new features or drivers are
being added so syzbot reports are not for a new bugs (regressions) and
are not a priority (at least to me).

I have only resources to review/merge pending fbdev patches from time
to time so any help in fixing these syzbot reports is welcomed (there
have been a few fbdev related syzbot reports recently).

Also please note that fbdev is maintained through drm-misc tree so
patches can also be handled by other drm-misc maintainers in case I'm
not available / busy with other things.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

>>>  wake_up_worker kernel/workqueue.c:836 [inline]
>>>  insert_work+0x2ad/0x3a0 kernel/workqueue.c:1337
>>>  __queue_work+0x50d/0x1280 kernel/workqueue.c:1488
>>>  call_timer_fn+0x195/0x760 kernel/time/timer.c:1404
>>>  expire_timers kernel/time/timer.c:1444 [inline]
>>>  __run_timers kernel/time/timer.c:1773 [inline]
>>>  __run_timers kernel/time/timer.c:1740 [inline]
>>>  run_timer_softirq+0x412/0x1600 kernel/time/timer.c:1786
>>>  __do_softirq+0x26c/0x99d kernel/softirq.c:292
>>>  invoke_softirq kernel/softirq.c:373 [inline]
>>>  irq_exit+0x192/0x1d0 kernel/softirq.c:413
>>>  exiting_irq arch/x86/include/asm/apic.h:546 [inline]
>>>  smp_apic_timer_interrupt+0x19e/0x600 arch/x86/kernel/apic/apic.c:1146
>>>  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
>>>  </IRQ>