unregister_netdevice: waiting for lo to become free. Usage count = 2
unregister_netdevice: waiting for lo to become free. Usage count = 2
unregister_netdevice: waiting for lo to become free. Usage count = 2
unregister_netdevice: waiting for lo to become free. Usage count = 2
unregister_netdevice: waiting for lo to become free. Usage count = 2
INFO: task syz-executor5:6267 blocked for more than 120 seconds.
      Not tainted 4.4.116-g17c7c49 #17
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D ffff8801cf907768 29544  6267   3853 0x00000004
 ffff8801cf907768 0000000000000000 0000000000000000 0000000000000000
 0000000000000001 ffff8801cf907700 ffff8801db21fdb8 ffff8801db21fde0
 ffff8801db21f4d8 ffff8800b997e000 ffff8800b997c800 0000000000000000
Call Trace:
 [<ffffffff837668ca>] schedule+0x7a/0x1b0 kernel/sched/core.c:3353
 [<ffffffff837670c3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3386
 [<ffffffff8376b686>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8376b686>] mutex_lock_nested+0x306/0x850 kernel/locking/mutex.c:621
 [<ffffffff82d42a7f>] odev_open+0x5f/0x90 sound/core/seq/oss/seq_oss.c:136
 [<ffffffff82ca1a01>] soundcore_open+0x321/0x630 sound/sound_core.c:639
 [<ffffffff81529d8b>] chrdev_open+0x22b/0x4c0 fs/char_dev.c:388
 [<ffffffff81517f5b>] do_dentry_open+0x59b/0xba0 fs/open.c:749
 [<ffffffff8151b820>] vfs_open+0x110/0x210 fs/open.c:862
 [<ffffffff8154ca83>] do_last fs/namei.c:3217 [inline]
 [<ffffffff8154ca83>] path_openat+0x923/0x3940 fs/namei.c:3353
 [<ffffffff81552727>] do_filp_open+0x197/0x290 fs/namei.c:3388
 [<ffffffff8151c1f9>] do_sys_open+0x369/0x660 fs/open.c:1038
 [<ffffffff8151c560>] SYSC_openat fs/open.c:1065 [inline]
 [<ffffffff8151c560>] SyS_openat+0x30/0x40 fs/open.c:1059
 [<ffffffff83774a1f>] entry_SYSCALL_64_fastpath+0x1c/0x98
INFO: lockdep is turned off.
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 486 Comm: khungtaskd Not tainted 4.4.116-g17c7c49 #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb0fc800 task.stack: ffff8800bb3b0000
RIP: 0010:[<ffffffff810c3eb7>]  [<ffffffff810c3eb7>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c3eb7>]  [<ffffffff810c3eb7>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c3eb7>]  [<ffffffff810c3eb7>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c3eb7>]  [<ffffffff810c3eb7>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bb3b7cb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: ffffffff8126a2f2
RDX: 0000000000000c00 RSI: 0000000000000002 RDI: ffffffffff5fb300
RBP: ffff8800bb3b7ce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: fffffbfff0ad7e24 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426f3e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f609590a000 CR3: 00000001d98a6000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426f3e0 ffffffff847ef800 fffffbfff08fd9b4 dffffc0000000000
 ffff8801db31bca0 ffff8800bb3b7d00 ffffffff810b99eb ffffffff839f61c0
 0000000000000003 ffff8800bb3b7d60 ffffffff81d0eed4 0000000000000001
Call Trace:
 [<ffffffff810b99eb>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d0eed4>] nmi_trigger_all_cpu_backtrace+0x4a4/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b9a84>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff81368caa>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff81368caa>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368caa>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368caa>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff811907e8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff83774e45>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:506
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 7b 2f 17 00 4c 89 e7 57 9d 0f 1f 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.116-g17c7c49 #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9b49800 task.stack: ffff8801d9b58000
RIP: 0010:[<ffffffff810d0536>]  [<ffffffff810d0536>] native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:49
RSP: 0018:ffff8801d9b5fd98  EFLAGS: 00000246
RAX: 0000000000000003 RBX: ffffffff847dd908 RCX: ffffffff81d63d1b
RDX: 0000000000000004 RSI: ffffffff839fe320 RDI: ffffffff84418180
RBP: ffff8801d9b5fd98 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 1ffff1003b36bf82 R12: 0000000000000001
R13: fffffbfff070887c R14: ffffffff847ebc78 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c422ea7c00 CR3: 00000001c4850000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d9b5fdd0 ffffffff81027ed5 ffff8801d9b60000 ffffffff847dd908
 fffffbfff070887c ffffffff847ebc78 0000000000000000 ffff8801d9b5fde0
 ffffffff8102944a ffff8801d9b5fdf8 ffffffff812214c8 dffffc0000000000
Call Trace:
 [<ffffffff81027ed5>] arch_safe_halt arch/x86/include/asm/paravirt.h:117 [inline]
 [<ffffffff81027ed5>] default_idle+0x55/0x3c0 arch/x86/kernel/process.c:290
 [<ffffffff8102944a>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:281
 [<ffffffff812214c8>] default_idle_call+0x48/0x70 kernel/sched/idle.c:93
 [<ffffffff81221bcd>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff81221bcd>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff81221bcd>] cpu_startup_entry+0x5fd/0x8f0 kernel/sched/idle.c:301
 [<ffffffff810adcb4>] start_secondary+0x304/0x3e0 arch/x86/kernel/smpboot.c:242
Code: 00 00 00 00 00 55 48 89 e5 fa 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 66 0f 1f 84