audit: type=1400 audit(1556795271.647:7335): avc:  denied  { search } for  pid=20886 comm="udevd" name="/" dev="sysfs" ino=1 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:zero_device_t:s0 tclass=dir permissive=1
INFO: task kworker/u4:2:20312 blocked for more than 140 seconds.
      Not tainted 4.4.174+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:2    D ffff8800b2f3f968 25880 20312      2 0x80000000
Workqueue: netns cleanup_net
 ffff8800b2f3f968 ffff8800b9218000 49916ce589ab9914 ffff8800b9218000
 0000000000000002 ffff8800b9218800 ffff8801db61f180 ffff8801db61f1a8
 ffff8801db61e898 ffff8801d7774740 ffff8800b9218000 ffffed00165e7001
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
 [<ffffffff8221a971>] cleanup_net+0x131/0x860 net/core/net_namespace.c:418
 [<ffffffff81122c25>] process_one_work+0x825/0x1720 kernel/workqueue.c:2064
 [<ffffffff81124004>] worker_thread+0x4e4/0xf50 kernel/workqueue.c:2196
 [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
 [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537
3 locks held by kworker/u4:2/20312:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff81122b0a>] process_one_work+0x70a/0x1720 kernel/workqueue.c:2057
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff81122b42>] process_one_work+0x742/0x1720 kernel/workqueue.c:2061
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff8221a971>] cleanup_net+0x131/0x860 net/core/net_namespace.c:418
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 25333 Comm: syz-executor.4 Not tainted 4.4.174+ #4
task: ffff8801b63117c0 task.stack: ffff8801b6348000
RIP: 0010:[<ffffffff81483ceb>]  [<ffffffff81483ceb>] memory_is_zero mm/kasan/kasan.c:258 [inline]
RIP: 0010:[<ffffffff81483ceb>]  [<ffffffff81483ceb>] memory_is_poisoned_n mm/kasan/kasan.c:273 [inline]
RIP: 0010:[<ffffffff81483ceb>]  [<ffffffff81483ceb>] memory_is_poisoned mm/kasan/kasan.c:306 [inline]
RIP: 0010:[<ffffffff81483ceb>]  [<ffffffff81483ceb>] check_memory_region_inline mm/kasan/kasan.c:322 [inline]
RIP: 0010:[<ffffffff81483ceb>]  [<ffffffff81483ceb>] check_memory_region+0x7b/0x180 mm/kasan/kasan.c:332
RSP: 0018:ffff8801b634f678  EFLAGS: 00000206
RAX: ffffed0034b42590 RBX: ffffed0034b425a8 RCX: ffffffff821f7b91
RDX: 0000000000000001 RSI: 00000000000000c0 RDI: ffff8801a5a12c80
RBP: ffff8801b634f690 R08: 0000000000000003 R09: 0000000000000018
R10: ffffed0034b425a7 R11: ffff8801a5a12d3f R12: ffffed0034b42590
R13: 00000000000000c0 R14: 0000000000000000 R15: 0000000000000200
FS:  00007f0f633e7700(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000001b6329000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff88018a94d180 ffff8801a5a12c80 00000000000000c0 ffff8801b634f6b8
 ffffffff81484244 ffff8801a5a12c80 ffff88018a94d240 ffff8801b634f738
 ffff8801b634f760 ffffffff821f7b91 000000c000000000 1ffff10036c69edb
Call Trace:
 [<ffffffff81484244>] memset+0x24/0x40 mm/kasan/kasan.c:350
 [<ffffffff821f7b91>] __alloc_skb+0x161/0x5d0 net/core/skbuff.c:245
 [<ffffffff81ab5f52>] alloc_skb include/linux/skbuff.h:820 [inline]
 [<ffffffff81ab5f52>] kobject_uevent_env+0x582/0xba0 lib/kobject_uevent.c:300
 [<ffffffff81ab6590>] kobject_uevent+0x20/0x30 lib/kobject_uevent.c:374
 [<ffffffff81cfd02c>] device_add+0xa3c/0x1490 drivers/base/core.c:1141
 [<ffffffff8229462d>] netdev_register_kobject+0x12d/0x300 net/core/net-sysfs.c:1549
 [<ffffffff8224b059>] register_netdevice+0x669/0xcc0 net/core/dev.c:6807
 [<ffffffff8224b6cb>] register_netdev+0x1b/0x30 net/core/dev.c:6919
 [<ffffffff826a527e>] sit_init_net+0x2de/0x850 net/ipv6/sit.c:1833
 [<ffffffff82217370>] ops_init+0xb0/0x3a0 net/core/net_namespace.c:109
 [<ffffffff82219494>] setup_net+0x1b4/0x4e0 net/core/net_namespace.c:289
 [<ffffffff8221b175>] copy_net_ns+0xd5/0x250 net/core/net_namespace.c:388
 [<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
audit_printk_skb: 135 callbacks suppressed
audit: type=1400 audit(1556795276.117:7381): avc:  denied  { search } for  pid=469 comm="udevd" name="/" dev="sysfs" ino=1 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:zero_device_t:s0 tclass=dir permissive=1
 [<ffffffff82718cb7>] tracesys+0x88/0x8d
Code: 8d 5a 01 49 89 d9 4d 29 e1 49 83 f9 10 0f 8e b8 00 00 00 45 89 e0 41 83 e0 07 75 56 4d 8d 41 07 4d 85 c9 4d 0f 49 c1 49 c1 f8 03 <45> 85 c0 0f 84 f3 00 00 00 41 83 e8 01 4e 8d 44 c0 08 eb 0d 48 
NMI backtrace for cpu 1
CPU: 1 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4
task: ffff8801da6f4740 task.stack: ffff8800001d0000
audit: type=1400 audit(1556795276.177:7382): avc:  denied  { search } for  pid=20886 comm="udevd" name="/" dev="sysfs" ino=1 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:zero_device_t:s0 tclass=dir permissive=1
audit: type=1400 audit(1556795276.197:7383): avc:  denied  { search } for  pid=20886 comm="udevd" name="/" dev="sysfs" ino=1 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:zero_device_t:s0 tclass=dir permissive=1
audit: type=1400 audit(1556795276.197:7384): avc:  denied  { search } for  pid=20886 comm="udevd" name="/" dev="sysfs" ino=1 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:zero_device_t:s0 tclass=dir permissive=1
audit: type=1400 audit(1556795276.197:7385): avc:  denied  { search } for  pid=20886 comm="udevd" name="/" dev="sysfs" ino=1 scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:object_r:zero_device_t:s0 tclass=dir permissive=1
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: 00007f4aab99a000 CR3: 00000000ba15e000 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