Hello,

syzbot found the following issue on:

HEAD commit: dff9f829 Add linux-next specific files for 20200908 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1425773e900000 kernel config: https://syzkaller.appspot.com/x/.config?x=37b3426c77bda44c dashboard link: https://syzkaller.appspot.com/bug?extid=561a74f84100162990b2 compiler: gcc (GCC) 10.1.0-syz 20200507 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=126577ae900000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=121e4e21900000

IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+561a74f84100162990b2@syzkaller.appspotmail.com

======================================================== WARNING: possible irq lock inversion dependency detected 5.9.0-rc4-next-20200908-syzkaller #0 Not tainted -------------------------------------------------------- swapper/0/0 just changed the state of lock: ffff8882153bc908 (&group->lock){..-.}-{2:2}, at: _snd_pcm_stream_lock_irqsave+0x9f/0xd0 sound/core/pcm_native.c:170 but this lock took another, SOFTIRQ-READ-unsafe lock in the past: (&card->ctl_files_rwlock){.+.+}-{2:2}

and interrupts could create inverse lock ordering between them.

other info that might help us debug this: Possible interrupt unsafe locking scenario:

CPU0 CPU1 ---- ---- lock(&card->ctl_files_rwlock); local_irq_disable(); lock(&group->lock); lock(&card->ctl_files_rwlock); <Interrupt> lock(&group->lock);

*** DEADLOCK ***

1 lock held by swapper/0/0: #0: ffffc90000007d68 ((&dpcm->timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:35 [inline] #0: ffffc90000007d68 ((&dpcm->timer)){+.-.}-{0:0}, at: call_timer_fn+0xdb/0x760 kernel/time/timer.c:1403

the shortest dependencies between 2nd lock and 1st lock: -> (&card->ctl_files_rwlock){.+.+}-{2:2} { HARDIRQ-ON-R at: lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x5b/0x70 kernel/locking/spinlock.c:223 snd_ctl_notify.part.0+0x36/0x550 sound/core/control.c:153 snd_ctl_notify+0x8f/0xb0 sound/core/control.c:181 __snd_ctl_add_replace+0x638/0x800 sound/core/control.c:382 snd_ctl_add_replace+0x76/0x130 sound/core/control.c:399 snd_card_dummy_new_mixer sound/drivers/dummy.c:885 [inline] snd_dummy_probe+0xbbf/0x1050 sound/drivers/dummy.c:1080 platform_drv_probe+0x87/0x140 drivers/base/platform.c:747 really_probe+0x282/0x9f0 drivers/base/dd.c:553 driver_probe_device+0xfe/0x1d0 drivers/base/dd.c:738 __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:844 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431 __device_attach+0x228/0x470 drivers/base/dd.c:912 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 device_add+0xb17/0x1c40 drivers/base/core.c:2926 platform_device_add+0x34f/0x6d0 drivers/base/platform.c:597 platform_device_register_full+0x38c/0x4e0 drivers/base/platform.c:720 platform_device_register_resndata include/linux/platform_device.h:131 [inline] platform_device_register_simple include/linux/platform_device.h:160 [inline] alsa_card_dummy_init+0x1cc/0x2e0 sound/drivers/dummy.c:1168 do_one_initcall+0x10a/0x7b0 init/main.c:1204 do_initcall_level init/main.c:1277 [inline] do_initcalls init/main.c:1293 [inline] do_basic_setup init/main.c:1313 [inline] kernel_init_freeable+0x5e9/0x66d init/main.c:1512 kernel_init+0xd/0x1c0 init/main.c:1402 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 SOFTIRQ-ON-R at: lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x5b/0x70 kernel/locking/spinlock.c:223 snd_ctl_notify.part.0+0x36/0x550 sound/core/control.c:153 snd_ctl_notify+0x8f/0xb0 sound/core/control.c:181 __snd_ctl_add_replace+0x638/0x800 sound/core/control.c:382 snd_ctl_add_replace+0x76/0x130 sound/core/control.c:399 snd_card_dummy_new_mixer sound/drivers/dummy.c:885 [inline] snd_dummy_probe+0xbbf/0x1050 sound/drivers/dummy.c:1080 platform_drv_probe+0x87/0x140 drivers/base/platform.c:747 really_probe+0x282/0x9f0 drivers/base/dd.c:553 driver_probe_device+0xfe/0x1d0 drivers/base/dd.c:738 __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:844 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431 __device_attach+0x228/0x470 drivers/base/dd.c:912 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 device_add+0xb17/0x1c40 drivers/base/core.c:2926 platform_device_add+0x34f/0x6d0 drivers/base/platform.c:597 platform_device_register_full+0x38c/0x4e0 drivers/base/platform.c:720 platform_device_register_resndata include/linux/platform_device.h:131 [inline] platform_device_register_simple include/linux/platform_device.h:160 [inline] alsa_card_dummy_init+0x1cc/0x2e0 sound/drivers/dummy.c:1168 do_one_initcall+0x10a/0x7b0 init/main.c:1204 do_initcall_level init/main.c:1277 [inline] do_initcalls init/main.c:1293 [inline] do_basic_setup init/main.c:1313 [inline] kernel_init_freeable+0x5e9/0x66d init/main.c:1512 kernel_init+0xd/0x1c0 init/main.c:1402 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 (null) at: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.9.0-rc4-next-20200908-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:print_lock_trace kernel/locking/lockdep.c:1751 [inline] RIP: 0010:print_lock_class_header kernel/locking/lockdep.c:2240 [inline] RIP: 0010:print_shortest_lock_dependencies.cold+0x110/0x2af kernel/locking/lockdep.c:2263 Code: 48 8b 04 24 48 c1 e8 03 42 80 3c 20 00 74 09 48 8b 3c 24 e8 dd fb de f9 48 8b 04 24 48 8b 00 48 8d 78 14 48 89 fa 48 c1 ea 03 <42> 0f b6 0c 22 48 89 fa 83 e2 07 83 c2 03 38 ca 7c 08 84 c9 0f 85 RSP: 0018:ffffc90000007870 EFLAGS: 00010003 RAX: 0000000000000001 RBX: ffffffff8c8d3cc0 RCX: 0000000000000000 RDX: 0000000000000002 RSI: ffffffff815bc817 RDI: 0000000000000015 RBP: ffffc900000079a0 R08: 0000000000000004 R09: ffff8880ae620f8b R10: 0000000000000000 R11: 6c756e2820202020 R12: dffffc0000000000 R13: ffffffff8c6de1d0 R14: 0000000000000009 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000200000c0 CR3: 0000000093f18000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> print_irq_inversion_bug.part.0+0x2c6/0x2ee kernel/locking/lockdep.c:3769 print_irq_inversion_bug kernel/locking/lockdep.c:4377 [inline] check_usage_forwards kernel/locking/lockdep.c:3803 [inline] mark_lock_irq kernel/locking/lockdep.c:3935 [inline] mark_lock.cold+0x38/0x10d kernel/locking/lockdep.c:4375 mark_usage kernel/locking/lockdep.c:4260 [inline] __lock_acquire+0x117d/0x55d0 kernel/locking/lockdep.c:4750 lock_acquire+0x1f3/0xaf0 kernel/locking/lockdep.c:5398 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x94/0xd0 kernel/locking/spinlock.c:159 _snd_pcm_stream_lock_irqsave+0x9f/0xd0 sound/core/pcm_native.c:170 snd_pcm_period_elapsed+0x24/0x250 sound/core/pcm_lib.c:1799 loopback_jiffies_timer_function+0x1a8/0x220 sound/drivers/aloop.c:669 call_timer_fn+0x1ac/0x760 kernel/time/timer.c:1413 expire_timers kernel/time/timer.c:1458 [inline] __run_timers.part.0+0x67c/0xaa0 kernel/time/timer.c:1755 __run_timers kernel/time/timer.c:1736 [inline] run_timer_softirq+0xae/0x1a0 kernel/time/timer.c:1768 __do_softirq+0x1f7/0xa91 kernel/softirq.c:298 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706 </IRQ> __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline] do_softirq_own_stack+0x9d/0xd0 arch/x86/kernel/irq_64.c:77 invoke_softirq kernel/softirq.c:393 [inline] __irq_exit_rcu kernel/softirq.c:423 [inline] irq_exit_rcu+0x235/0x280 kernel/softirq.c:435 sysvec_apic_timer_interrupt+0x51/0xf0 arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581 RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61 Code: ff 4c 89 ef e8 23 c4 b4 f9 e9 8e fe ff ff 48 89 df e8 16 c4 b4 f9 eb 8a cc cc cc cc e9 07 00 00 00 0f 00 2d 94 f6 4a 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 84 f6 4a 00 f4 c3 cc cc 55 53 e8 e9 RSP: 0018:ffffffff89a07cd8 EFLAGS: 00000293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffffffff15796a9 RDX: ffffffff89a99dc0 RSI: ffffffff87fdd050 RDI: 0000000000000000 RBP: ffff8880a67b3064 R08: 0000000000000001 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000001 R12: ffff8880a67b3064 R13: 1ffffffff1340fa5 R14: ffff8880a67b3065 R15: 0000000000000001 arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline] acpi_safe_halt+0x95/0x180 drivers/acpi/processor_idle.c:111 acpi_idle_do_entry+0x15c/0x1b0 drivers/acpi/processor_idle.c:524 acpi_idle_enter+0x403/0xac0 drivers/acpi/processor_idle.c:650 cpuidle_enter_state+0x150/0xa70 drivers/cpuidle/cpuidle.c:243 cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:355 call_cpuidle kernel/sched/idle.c:132 [inline] cpuidle_idle_call kernel/sched/idle.c:213 [inline] do_idle+0x48e/0x730 kernel/sched/idle.c:273 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:369 start_kernel+0x490/0x4b1 init/main.c:1048 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 Modules linked in: ---[ end trace 7b8dcf330d33be72 ]--- RIP: 0010:print_lock_trace kernel/locking/lockdep.c:1751 [inline] RIP: 0010:print_lock_class_header kernel/locking/lockdep.c:2240 [inline] RIP: 0010:print_shortest_lock_dependencies.cold+0x110/0x2af kernel/locking/lockdep.c:2263 Code: 48 8b 04 24 48 c1 e8 03 42 80 3c 20 00 74 09 48 8b 3c 24 e8 dd fb de f9 48 8b 04 24 48 8b 00 48 8d 78 14 48 89 fa 48 c1 ea 03 <42> 0f b6 0c 22 48 89 fa 83 e2 07 83 c2 03 38 ca 7c 08 84 c9 0f 85 RSP: 0018:ffffc90000007870 EFLAGS: 00010003 RAX: 0000000000000001 RBX: ffffffff8c8d3cc0 RCX: 0000000000000000 RDX: 0000000000000002 RSI: ffffffff815bc817 RDI: 0000000000000015 RBP: ffffc900000079a0 R08: 0000000000000004 R09: ffff8880ae620f8b R10: 0000000000000000 R11: 6c756e2820202020 R12: dffffc0000000000 R13: ffffffff8c6de1d0 R14: 0000000000000009 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000200000c0 CR3: 0000000093f18000 CR4: 00000000001506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

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