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To:     "Zhang, Qiang" <Qiang.Zhang@windriver.com>,
        syzbot <syzbot+28abd693db9e92c160d8@syzkaller.appspotmail.com>,
        "asml.silence@gmail.com" <asml.silence@gmail.com>,
        "io-uring@vger.kernel.org" <io-uring@vger.kernel.org>,
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From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <6a210838-9ffa-5053-29f7-486c8c65f792@kernel.dk>
Date:   Sun, 28 Feb 2021 19:48:20 -0700
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On 2/28/21 7:08 PM, Zhang, Qiang wrote:
> 
> 
> ________________________________________
> ??????: Jens Axboe <axboe@kernel.dk>
> ????ʱ??: 2021??3??1?? 7:08
> ?ռ???: syzbot; asml.silence@gmail.com; io-uring@vger.kernel.org; linux-fsdevel@vger.kernel.org; linux-kernel@vger.kernel.org; syzkaller-bugs@googlegroups.com; viro@zeniv.linux.org.uk
> ????: Re: possible deadlock in io_poll_double_wake (2)
> 
> [Please note: This e-mail is from an EXTERNAL e-mail address]
> 
> On 2/27/21 5:42 PM, syzbot wrote:
>> syzbot has found a reproducer for the following issue on:
>>
>> HEAD commit:    5695e516 Merge tag 'io_uring-worker.v3-2021-02-25' of git:..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=114e3866d00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=8c76dad0946df1f3
>> dashboard link: https://syzkaller.appspot.com/bug?extid=28abd693db9e92c160d8
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=122ed9b6d00000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14d5a292d00000
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+28abd693db9e92c160d8@syzkaller.appspotmail.com
>>
>> ============================================
>> WARNING: possible recursive locking detected
>> 5.11.0-syzkaller #0 Not tainted
>> --------------------------------------------
>> swapper/1/0 is trying to acquire lock:
>> ffff88801b2b1130 (&runtime->sleep){..-.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
>> ffff88801b2b1130 (&runtime->sleep){..-.}-{2:2}, at: io_poll_double_wake+0x25f/0x6a0 fs/io_uring.c:4960
>>
>> but task is already holding lock:
>> ffff88801b2b3130 (&runtime->sleep){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137
>>
>> other info that might help us debug this:
>>  Possible unsafe locking scenario:
>>
>>        CPU0
>>        ----
>>   lock(&runtime->sleep);
>>   lock(&runtime->sleep);
>>
>>  *** DEADLOCK ***
>>
>>  May be due to missing lock nesting notation
>>
>> 2 locks held by swapper/1/0:
>>  #0: ffff888147474908 (&group->lock){..-.}-{2:2}, at: _snd_pcm_stream_lock_irqsave+0x9f/0xd0 sound/core/pcm_native.c:170
>>  #1: ffff88801b2b3130 (&runtime->sleep){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137
>>
>> stack backtrace:
>> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.11.0-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:79 [inline]
>>  dump_stack+0xfa/0x151 lib/dump_stack.c:120
>>  print_deadlock_bug kernel/locking/lockdep.c:2829 [inline]
>>  check_deadlock kernel/locking/lockdep.c:2872 [inline]
>>  validate_chain kernel/locking/lockdep.c:3661 [inline]
>>  __lock_acquire.cold+0x14c/0x3b4 kernel/locking/lockdep.c:4900
>>  lock_acquire kernel/locking/lockdep.c:5510 [inline]
>>  lock_acquire+0x1ab/0x730 kernel/locking/lockdep.c:5475
>>  __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>>  _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
>>  spin_lock include/linux/spinlock.h:354 [inline]
>>  io_poll_double_wake+0x25f/0x6a0 fs/io_uring.c:4960
>>  __wake_up_common+0x147/0x650 kernel/sched/wait.c:108
>>  __wake_up_common_lock+0xd0/0x130 kernel/sched/wait.c:138
>>  snd_pcm_update_state+0x46a/0x540 sound/core/pcm_lib.c:203
>>  snd_pcm_update_hw_ptr0+0xa75/0x1a50 sound/core/pcm_lib.c:464
>>  snd_pcm_period_elapsed+0x160/0x250 sound/core/pcm_lib.c:1805
>>  dummy_hrtimer_callback+0x94/0x1b0 sound/drivers/dummy.c:378
>>  __run_hrtimer kernel/time/hrtimer.c:1519 [inline]
>>  __hrtimer_run_queues+0x609/0xe40 kernel/time/hrtimer.c:1583
>>  hrtimer_run_softirq+0x17b/0x360 kernel/time/hrtimer.c:1600
>>  __do_softirq+0x29b/0x9f6 kernel/softirq.c:345
>>  invoke_softirq kernel/softirq.c:221 [inline]
>>  __irq_exit_rcu kernel/softirq.c:422 [inline]
>>  irq_exit_rcu+0x134/0x200 kernel/softirq.c:434
>>  sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1100
>>  </IRQ>
>>  asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
>> RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:29 [inline]
>> RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:70 [inline]
>> RIP: 0010:arch_irqs_disabled arch/x86/include/asm/irqflags.h:137 [inline]
>> RIP: 0010:acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline]
>> RIP: 0010:acpi_idle_do_entry+0x1c9/0x250 drivers/acpi/processor_idle.c:516
>> Code: dd 38 6e f8 84 db 75 ac e8 54 32 6e f8 e8 0f 1c 74 f8 e9 0c 00 00 00 e8 45 32 6e f8 0f 00 2d 4e 4a c5 00 e8 39 32 6e f8 fb f4 <9c> 5b 81 e3 00 02 00 00 fa 31 ff 48 89 de e8 14 3a 6e f8 48 85 db
>> RSP: 0018:ffffc90000d47d18 EFLAGS: 00000293
>> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
>> RDX: ffff8880115c3780 RSI: ffffffff89052537 RDI: 0000000000000000
>> RBP: ffff888141127064 R08: 0000000000000001 R09: 0000000000000001
>> R10: ffffffff81794168 R11: 0000000000000000 R12: 0000000000000001
>> R13: ffff888141127000 R14: ffff888141127064 R15: ffff888143331804
>>  acpi_idle_enter+0x361/0x500 drivers/acpi/processor_idle.c:647
>>  cpuidle_enter_state+0x1b1/0xc80 drivers/cpuidle/cpuidle.c:237
>>  cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:351
>>  call_cpuidle kernel/sched/idle.c:158 [inline]
>>  cpuidle_idle_call kernel/sched/idle.c:239 [inline]
>>  do_idle+0x3e1/0x590 kernel/sched/idle.c:300
>>  cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:397
>>  start_secondary+0x274/0x350 arch/x86/kernel/smpboot.c:272
>>  secondary_startup_64_no_verify+0xb0/0xbb
> 
>> This looks very odd, only thing I can think of is someone >doing
>> poll_wait() twice with different entries but for the same
>> waitqueue head.
>>
> 
> Hello  Jens Axboe
> 
> here poll_wait() twice in waitqueue head 'runtime->sleep'
> in sound/core/oss/pcm_oss.c
> 
> static __poll_t snd_pcm_oss_poll(struct file *file, poll_table * wait) {
> ...........
>         if (psubstream != NULL) {
>                 struct snd_pcm_runtime *runtime = psubstream->runtime;
>                 poll_wait(file, &runtime->sleep, wait);
>                 snd_pcm_stream_lock_irq(psubstream);
>                 if (runtime->status->state != SNDRV_PCM_STATE_DRAINING &&
>                     (runtime->status->state != SNDRV_PCM_STATE_RUNNING ||
>                      snd_pcm_oss_playback_ready(psubstream)))
>                         mask |= EPOLLOUT | EPOLLWRNORM;
>                 snd_pcm_stream_unlock_irq(psubstream);
>         }
>         if (csubstream != NULL) {
>                 struct snd_pcm_runtime *runtime = csubstream->runtime;
>                 snd_pcm_state_t ostate;
>                 poll_wait(file, &runtime->sleep, wait);
>                 snd_pcm_stream_lock_irq(csubstream);
> ..........
> }
> 
>  I don't know if there are any other drivers that use the same way ,   can add some judgment in io_poll_double_wake()?

Right, that's what my post-email investigation led to as well, hence I queued
this one up:

https://git.kernel.dk/cgit/linux-block/commit/?h=io_uring-worker.v4&id=4a0a6fd611f5109bcfab4a95db836bb27131e3be

-- 
Jens Axboe