syzbot reports a deadlock, attempting to lock the same spinlock twice:

============================================ 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

which is due to the driver doing poll_wait() twice on the same wait_queue_head. That is perfectly valid, but from checking the rest of the kernel tree, it's the only driver that does this.

We can handle this just fine, we just need to ignore the second addition as we'll get woken just fine on the first one.

Cc: stable@vger.kernel.org # 5.8+ Fixes: 18bceab101ad ("io_uring: allow POLL_ADD with double poll_wait() users") Reported-by: syzbot+28abd693db9e92c160d8@syzkaller.appspotmail.com Signed-off-by: Jens Axboe axboe@kernel.dk --- fs/io_uring.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c index 549a5c5ee0b5..bdaeda5eefd5 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4959,6 +4959,9 @@ static void __io_queue_proc(struct io_poll_iocb *poll, struct io_poll_table *pt, pt->error = -EINVAL; return; } + /* double add on the same waitqueue head, ignore */ + if (poll->head == head) + return; poll = kmalloc(sizeof(*poll), GFP_ATOMIC); if (!poll) { pt->error = -ENOMEM;