linux-kernel - Re: time: hang due to timer_create/timer

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Date:   Fri, 21 Apr 2017 17:05:57 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andrey Konovalov <andreyknvl@...gle.com>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        syzkaller <syzkaller@...glegroups.com>,
        John Stultz <john.stultz@...aro.org>
Subject: Re: time: hang due to timer_create/timer_settime

On Fri, 21 Apr 2017, Andrey Konovalov wrote:
> Hi,
> 
> I've got the following error report while fuzzing the kernel with syzkaller.
> 
> On commit 4f7d029b9bf009fbee76bb10c0c4351a1870d2f3 (4.11-rc7).
> 
> A reproducer and .config are attached.
> 
> The program hangs the kernel.
>  lock_acquire+0x22d/0x560 kernel/locking/lockdep.c:3762
>  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>  _raw_spin_lock_irqsave+0xc4/0x110 kernel/locking/spinlock.c:159
>  alarmtimer_fired+0x169/0x7a0 kernel/time/alarmtimer.c:189
>  __run_hrtimer kernel/time/hrtimer.c:1212 [inline]
>  __hrtimer_run_queues+0x350/0xe50 kernel/time/hrtimer.c:1276
>  hrtimer_interrupt+0x1ab/0x5c0 kernel/time/hrtimer.c:1310
>  local_apic_timer_interrupt+0x6f/0xe0 arch/x86/kernel/apic/apic.c:937
>  smp_apic_timer_interrupt+0x71/0xa0 arch/x86/kernel/apic/apic.c:961
>  apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:487

Right. That lacks the protection which we have in the other posix
timers. I'll have a look.

Thanks,

	tglx