INFO: task syz-executor.0:14749 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.0  D ffff8800a0b1f9d8 29016 14749   2155 0x00000004
 ffff8800a0b1f9d8 ffff8801d0a04740 2fc48034be9ca9be ffff8801d0a04740
 0000000000000000 ffff8801d0a05000 ffff8801db71f180 ffff8801db71f1a8
 ffff8801db71e898 ffff8801d47d8000 ffff8801d0a04740 ffffed0014163001
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.0/14749:
 #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: 11995 Comm: syz-executor.4 Not tainted 4.4.174+ #4
task: ffff8801d47a2f80 task.stack: ffff8800a04d0000
RIP: 0010:[<ffffffff81013544>]  [<ffffffff81013544>] print_context_stack+0x54/0xd0 arch/x86/kernel/dumpstack.c:107
RSP: 0018:ffff8800a04d7990  EFLAGS: 00000283
RAX: ffff8800a04d7d48 RBX: ffff8800a04d7d18 RCX: 0000000000000005
RDX: ffff8800a04d7aa8 RSI: 0000000000000015 RDI: 0000000000000015
RBP: ffff8800a04d79d8 R08: ffff8800a04d7a90 R09: 0000000000000000
R10: ffff8800a04d7d48 R11: 0000000000000003 R12: 0000000000000000
R13: ffff8800a04d7a90 R14: ffff8800a04d7ff8 R15: ffff8800a04d0000
FS:  00007f55900b2700(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000090000003 CR3: 00000000b24c3000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000015 ffff8800a04d7d48 ffff8800a04d7d48 ffffffff8280f0b0
 ffff8800a04d7a90 ffffffff8280f0b0 ffff8800a04d7a30 ffff8801db607fc0
 0000000000000000 ffff8800a04d7a68 ffffffff81012bb9 ffff8800a04d7a2c
Call Trace:
 [<ffffffff81012bb9>] dump_trace+0x179/0x390 arch/x86/kernel/dumpstack_64.c:243
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff81483f22>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff81483f22>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff81483f22>] kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:616
 [<ffffffff81484197>] kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:601
 [<ffffffff8148475f>] kasan_slab_alloc+0xf/0x20 mm/kasan/kasan.c:554
 [<ffffffff8147fe9c>] slab_post_alloc_hook mm/slub.c:1349 [inline]
 [<ffffffff8147fe9c>] slab_alloc_node mm/slub.c:2615 [inline]
 [<ffffffff8147fe9c>] slab_alloc mm/slub.c:2623 [inline]
 [<ffffffff8147fe9c>] kmem_cache_alloc+0xdc/0x2c0 mm/slub.c:2628
 [<ffffffff814ca46c>] getname_flags+0xcc/0x550 fs/namei.c:135
 [<ffffffff814cb1df>] user_path_at_empty+0x2f/0x50 fs/namei.c:2403
 [<ffffffff815050a9>] user_path_dir include/linux/namei.h:67 [inline]
 [<ffffffff815050a9>] SYSC_pivot_root fs/namespace.c:3136 [inline]
 [<ffffffff815050a9>] SyS_pivot_root+0x139/0xea0 fs/namespace.c:3125
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: e4 48 89 4d d0 48 89 55 c8 74 5c 4c 39 e3 73 61 49 8d 84 24 00 80 ff ff 48 39 c3 72 54 48 8b 33 4c 89 55 c0 48 89 f7 48 89 75 b8 <e8> 97 bf 11 00 4c 8b 55 c0 85 c0 74 26 48 8b 45 d0 49 8d 52 08 
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: 0000000090000003 CR3: 00000001d6f4b000 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