On 3/31/20 12:18 PM, Dmitry Vyukov wrote:
On Tue, Mar 31, 2020 at 11:57 AM Peter Zijlstra [off-list ref] wrote:
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On Mon, Mar 30, 2020 at 10:01:12PM -0700, syzbot wrote:
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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?k56a78d-5a9a6c49-07572cc2-0cc47a314e9a-e4dc8b657d340686&u=https://syzkaller.appspot.com/x/log.txt?x06ed4be00000
kernel config: https://protect2.fireeye.com/url?kC211072-1eeddbb6-43209b3d-0cc47a314e9a-3bd45a19932c37c8&u=https://syzkaller.appspot.com/x/.config?x'392dd2975fd692
dashboard link: https://protect2.fireeye.com/url?k¿7a6153-e2b6aa97-bf7bea1c-0cc47a314e9a-c64073ee605efb7b&u=https://syzkaller.appspot.com/bug?extidè4d7ebd1361da13c356
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: <redacted>
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
b8ad06-517466c2-0cb92649-0cc47a314e9a-a20c11191483c65b&u=https://syzkaller.appspot.com/bug?idc7b2602b1ff40f0d34f38baa4ba1640727c3d9
https://protect2.fireeye.com/url?ka4292e3-3c8e5927-614319ac-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
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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>