INFO: task syz-executor.3:20678 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.3  D ffff8800964af9d8 27624 20678  20674 0x00000000
 ffff8800964af9d8 ffff8801a819c740 f0cb5a987a434aa4 ffff8801a819c740
 0000000000000000 ffff8801a819d000 ffff8801db71f180 ffff8801db71f1a8
 ffff8801db71e898 ffff8801d3054740 ffff8801a819c740 ffffed0012c95001
Call Trace:
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff8270a333>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388
 [<ffffffff8270c492>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8270c492>] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621
 [<ffffffff8221b16a>] copy_net_ns+0xca/0x250 net/core/net_namespace.c:387
 [<ffffffff81136a90>] create_new_namespaces+0x2f0/0x670 kernel/nsproxy.c:95
 [<ffffffff8113709a>] copy_namespaces+0x28a/0x320 kernel/nsproxy.c:150
 [<ffffffff810cd012>] copy_process+0x2472/0x68a0 kernel/fork.c:1522
 [<ffffffff810d186e>] _do_fork+0x14e/0xdc0 kernel/fork.c:1806
 [<ffffffff810d25b7>] SYSC_clone kernel/fork.c:1917 [inline]
 [<ffffffff810d25b7>] SyS_clone+0x37/0x50 kernel/fork.c:1911
 [<ffffffff82718cb7>] tracesys+0x88/0x8d
1 lock held by syz-executor.3/20678:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff8221b16a>] copy_net_ns+0xca/0x250 net/core/net_namespace.c:387
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 25933 Comm: syz-executor.5 Not tainted 4.4.174+ #4
task: ffff8801b1372f80 task.stack: ffff88009b998000
RIP: 0010:[<ffffffff811fdad6>]  [<ffffffff811fdad6>] mark_lock+0x16/0x1440 kernel/locking/lockdep.c:2900
RSP: 0018:ffff8801db607938  EFLAGS: 00000046
RAX: dffffc0000000000 RBX: 0000000000000060 RCX: 000000000000000c
RDX: 000000000000000c RSI: ffff8801b13738c0 RDI: ffff8801b1372f80
RBP: ffff8801db607940 R08: 0000000000000003 R09: ffff8801b13738e0
R10: ffffffff82836880 R11: 0000000000000000 R12: ffff8801b1372f80
R13: ffff8801b13738c0 R14: 0000000000000040 R15: 0000000000000000
FS:  00007fc600bd2700(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000040f880 CR3: 00000000a237b000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000000 ffff8801db607ad0 ffffffff811fffff ffff8801db6079e0
 ffff8801da555c80 ffff8801db6079b8 000000000000001d 1ffffffff0506d10
 ffff8801db607988 ffffffff8123a761 ffff8801db607a48 ffff8801b13738d8
Call Trace:
 <IRQ> 
d [<ffffffff811fffff>] __lock_acquire+0xa4f/0x4f50 kernel/locking/lockdep.c:3173
 [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82717e50>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
 [<ffffffff82717e50>] _raw_spin_lock_irqsave+0x50/0x70 kernel/locking/spinlock.c:159
 [<ffffffff8116799b>] try_to_wake_up+0x2b/0x1110 kernel/sched/core.c:1974
 [<ffffffff8116ab00>] wake_up_state+0x10/0x20 kernel/sched/core.c:2148
 [<ffffffff810f8764>] signal_wake_up_state+0x44/0x70 kernel/signal.c:659
 [<ffffffff810f9b3f>] signal_wake_up include/linux/sched.h:3337 [inline]
 [<ffffffff810f9b3f>] complete_signal+0x48f/0x7b0 kernel/signal.c:952
 [<ffffffff810ff1dd>] send_sigqueue+0x33d/0x8f0 kernel/signal.c:1570
 [<ffffffff81266ebd>] posix_timer_event+0x15d/0x270 kernel/time/posix-timers.c:437
 [<ffffffff8126706d>] posix_timer_fn+0x9d/0x290 kernel/time/posix-timers.c:465
 [<ffffffff8125fa5e>] __run_hrtimer kernel/time/hrtimer.c:1261 [inline]
 [<ffffffff8125fa5e>] __hrtimer_run_queues+0x34e/0xfc0 kernel/time/hrtimer.c:1325
 [<ffffffff81262756>] hrtimer_interrupt+0x1b6/0x450 kernel/time/hrtimer.c:1359
 [<ffffffff8108a9d6>] local_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:901
 [<ffffffff8271b249>] smp_apic_timer_interrupt+0x79/0xb0 arch/x86/kernel/apic/apic.c:925
 [<ffffffff8271a59d>] apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:768
 <EOI> 
d [<ffffffff8271806f>] ? arch_local_irq_enable arch/x86/include/asm/paravirt.h:822 [inline]
 <EOI> 
d [<ffffffff8271806f>] ? __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:170 [inline]
 <EOI> 
d [<ffffffff8271806f>] ? _raw_spin_unlock_irq+0x2f/0x60 kernel/locking/spinlock.c:199
 [<ffffffff811011ec>] spin_unlock_irq include/linux/spinlock.h:357 [inline]
 [<ffffffff811011ec>] get_signal+0xc6c/0x1570 kernel/signal.c:2324
 [<ffffffff8100bd4c>] do_signal+0x9c/0x1840 arch/x86/kernel/signal.c:712
 [<ffffffff81003da7>] exit_to_usermode_loop+0x127/0x170 arch/x86/entry/common.c:184
 [<ffffffff8100569b>] prepare_exit_to_usermode arch/x86/entry/common.c:221 [inline]
 [<ffffffff8100569b>] syscall_return_slowpath+0x25b/0x2e0 arch/x86/entry/common.c:286
 [<ffffffff82718ce1>] int_ret_from_sys_call+0x25/0xa3
Code: e9 62 ff ff ff 4c 89 f7 e8 e8 73 28 00 eb 9b 66 0f 1f 44 00 00 55 4c 8d 4e 20 89 d1 48 b8 00 00 00 00 00 fc ff df 48 89 e5 41 57 <41> 89 d7 4c 89 ca 41 56 48 c1 ea 03 41 be 01 00 00 00 41 55 41 
NMI backtrace for cpu 1
CPU: 1 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6f4740 task.stack: ffff8800001d0000
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline]
RIP: 0010:[<ffffffff8109b617>]  [<ffffffff8109b617>] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800001d7c88  EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300
RBP: ffff8800001d7cb8 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000b9157000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34
 000000000001b6c0 0000000000000008 ffff8800001d7cd8 ffffffff81092bee
 0000000000000008 ffffffff82924260 ffff8800001d7d30 ffffffff81ab8252
Call Trace:
 [<ffffffff81092bee>] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81ab8252>] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae lib/nmi_backtrace.c:85
 [<ffffffff81092ca4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff813b4762>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff813b4762>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813b4762>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813b4762>] watchdog.cold+0xd3/0xee kernel/hung_task.c:238
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1