On 3/31/20 12:18 PM, Dmitry Vyukov wrote:
On Tue, Mar 31, 2020 at 11:57 AM Peter Zijlstra peterz@infradead.org 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-e... kernel config: https://protect2.fireeye.com/url?k=43211072-1eeddbb6-43209b3d-0cc47a314e9a-3... dashboard link: https://protect2.fireeye.com/url?k=bf7a6153-e2b6aa97-bf7bea1c-0cc47a314e9a-c... 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@syzkaller.appspotmail.com
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-a... https://protect2.fireeye.com/url?k=614292e3-3c8e5927-614319ac-0cc47a314e9a-a...
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>