Date:   Sat, 7 Apr 2018 13:58:16 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+adc909755650e074e501@...kaller.appspotmail.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com
Subject: Re: INFO: rcu detected stall in snd_pcm_oss_write2

#syz dup: INFO: rcu detected stall in io_playback_transfer

On Fri, Apr 6, 2018 at 2:04 PM, syzbot
<syzbot+adc909755650e074e501@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> e02d37bf55a9a36f22427fd6dd733fe104d817b6 (Thu Apr 5 17:42:07 2018 +0000)
> Merge tag 'sound-4.17-rc1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=adc909755650e074e501
>
> So far this crash happened 2 times on upstream.
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=4567980574769152
> Kernel config:
> https://syzkaller.appspot.com/x/.config?id=-4805825610197092128
> compiler: gcc (GCC) 8.0.1 20180301 (experimental)
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+adc909755650e074e501@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
>         reason=80000021 qualification=0000000000000000
> IDTVectoring: info=00000000 errcode=00000000
> TSC Offset = 0xfffffd92e6bf78df
> TPR Threshold = 0x00
> EPT pointer = 0x00000001ab93b01e
> INFO: rcu_sched self-detected stall on CPU
>         0-....: (124999 ticks this GP) idle=81a/1/4611686018427387906
> softirq=379270/379270 fqs=31240
>          (t=125000 jiffies g=195733 c=195732 q=734)
> NMI backtrace for cpu 0
> CPU: 0 PID: 9961 Comm: syz-executor2 Not tainted 4.16.0+ #2
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x1b9/0x29f lib/dump_stack.c:53
>  nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
>  nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
>  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
>  trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline]
>  rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1376
>  print_cpu_stall kernel/rcu/tree.c:1525 [inline]
>  check_cpu_stall.isra.61.cold.80+0x36c/0x59a kernel/rcu/tree.c:1593
>  __rcu_pending kernel/rcu/tree.c:3356 [inline]
>  rcu_pending kernel/rcu/tree.c:3401 [inline]
>  rcu_check_callbacks+0x21b/0xad0 kernel/rcu/tree.c:2763
>  update_process_times+0x2d/0x70 kernel/time/timer.c:1636
>  tick_sched_handle+0xa0/0x180 kernel/time/tick-sched.c:171
>  tick_sched_timer+0x42/0x130 kernel/time/tick-sched.c:1179
>  __run_hrtimer kernel/time/hrtimer.c:1337 [inline]
>  __hrtimer_run_queues+0x3e3/0x10a0 kernel/time/hrtimer.c:1399
>  hrtimer_interrupt+0x286/0x650 kernel/time/hrtimer.c:1457
>  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
>  smp_apic_timer_interrupt+0x15d/0x710 arch/x86/kernel/apic/apic.c:1050
>  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:862
>  </IRQ>
> RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0x20 kernel/kcov.c:183
> RSP: 0018:ffff88018e3fee20 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff85a132bd
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffff88018e3fee70 R08: ffff88018e044100 R09: 0000000000000006
> R10: ffff88018e044100 R11: 0000000000000000 R12: 0000000000000001
> R13: ffff8801ceaa2d80 R14: ffff88019269ab00 R15: ffffffffffffffe0
>  snd_pcm_oss_write2+0x34c/0x460 sound/core/oss/pcm_oss.c:1373
>  snd_pcm_oss_sync1+0x332/0x5a0 sound/core/oss/pcm_oss.c:1606
>  snd_pcm_oss_sync.isra.29+0x790/0x980 sound/core/oss/pcm_oss.c:1682
>  snd_pcm_oss_release+0x214/0x290 sound/core/oss/pcm_oss.c:2559
>  __fput+0x34d/0x890 fs/file_table.c:209
>  ____fput+0x15/0x20 fs/file_table.c:243
>  task_work_run+0x1e4/0x290 kernel/task_work.c:113
>  exit_task_work include/linux/task_work.h:22 [inline]
>  do_exit+0x1aee/0x2730 kernel/exit.c:865
>  do_group_exit+0x16f/0x430 kernel/exit.c:968
>  get_signal+0x886/0x1960 kernel/signal.c:2469
>  do_signal+0x90/0x2020 arch/x86/kernel/signal.c:810
>  exit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_64+0x792/0x9d0 arch/x86/entry/common.c:292
>  entry_SYSCALL_64_after_hwframe+0x42/0xb7
> RIP: 0033:0x4552d9
> RSP: 002b:00007f0bfca8cce8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: fffffffffffffe00 RBX: 000000000072bf80 RCX: 00000000004552d9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000072bf80
> RBP: 000000000072bf80 R08: 0000000000000000 R09: 000000000072bf58
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 0000000000a3e81f R14: 00007f0bfca8d9c0 R15: 0000000000000001
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
> #syz fix: exact-commit-title
> To mark this as a duplicate of another syzbot report, please reply with:
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> If it's a one-off invalid bug report, please reply with:
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