======================================
| [  131.296968][   T71] ==================================================================
| [  131.297422][   T71] BUG: KASAN: null-ptr-deref in try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
| [  131.297892][   T71] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/71
| [  131.298335][   T71]
[  131.298485][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  131.298489][   T71] Workqueue: netns cleanup_net
[  131.298505][   T71] Call Trace:
[  131.298508][   T71]  <TASK>
[  131.298512][   T71]  dump_stack_lvl (lib/dump_stack.c:123)
[  131.298525][   T71]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  131.298530][   T71]  kasan_report (mm/kasan/report.c:597)
[  131.298546][   T71]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  131.298554][   T71]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[  131.298559][   T71]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  131.298566][   T71]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  131.298571][   T71]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  131.298578][   T71]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  131.298589][   T71]  __cancel_work_sync (kernel/workqueue.c:4383)
[  131.298595][   T71]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  131.298602][   T71]  ? netdev_notify_peers (net/core/dev.c:1891)
[  131.298608][   T71]  ? netif_close_many (net/core/dev.c:1959)
[  131.298615][   T71]  netif_close_many (net/core/dev.c:1959)
[  131.298620][   T71]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  131.298630][   T71]  ? __dev_close_many (net/core/dev.c:1949)
[  131.298636][   T71]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  131.298643][   T71]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  131.298651][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  131.298658][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  131.298663][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  131.298666][   T71]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  131.298672][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  131.298681][   T71]  default_device_exit_batch (net/core/dev.c:13229)
[  131.298687][   T71]  ? unregister_netdev (net/core/dev.c:13204)
[  131.298696][   T71]  ops_undo_list (net/core/net_namespace.c:251)
[  131.298708][   T71]  ? netns_get (net/core/net_namespace.c:223)
[  131.298712][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  131.298720][   T71]  cleanup_net (net/core/net_namespace.c:698)
[  131.298725][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[  131.298730][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  131.298743][   T71]  process_one_work (kernel/workqueue.c:3268)
[  131.298753][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  131.298761][   T71]  ? assign_work (kernel/workqueue.c:1206)
[  131.298768][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  131.298777][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[  131.298782][   T71]  kthread (kernel/kthread.c:463)
[  131.298787][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  131.298791][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  131.298799][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  131.298805][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  131.298809][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  131.298814][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[  131.298819][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  131.298823][   T71]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  131.312960][   T71] #PF: error_code(0x0002) - not-present page
| [  131.313252][   T71] PGD 0 P4D 0
| [  131.313438][   T71] Oops: Oops: 0002 [#1] SMP KASAN
| [  131.314220][   T71] Tainted: [B]=BAD_PAGE
[  131.314412][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  131.314917][   T71] Workqueue: netns cleanup_net
[  131.315106][   T71] RIP: 0010:try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  131.315339][   T71] Code: 00 41 89 c0 b8 01 00 00 00 45 85 c0 74 0f 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 be 08 00 00 00 48 89 df e8 df 81 84 00 <f0> 48 0f ba 2b 00 72 11 48 83 c4 10 31 c0 5b 5d 41 5c 41 5d 41 5e
All code
========
   0:	00 41 89             	add    %al,-0x77(%rcx)
   3:	c0 b8 01 00 00 00 45 	sarb   $0x45,0x1(%rax)
   a:	85 c0                	test   %eax,%eax
   c:	74 0f                	je     0x1d
   e:	48 83 c4 10          	add    $0x10,%rsp
  12:	5b                   	pop    %rbx
  13:	5d                   	pop    %rbp
  14:	41 5c                	pop    %r12
  16:	41 5d                	pop    %r13
  18:	41 5e                	pop    %r14
  1a:	41 5f                	pop    %r15
  1c:	c3                   	ret
  1d:	be 08 00 00 00       	mov    $0x8,%esi
  22:	48 89 df             	mov    %rbx,%rdi
  25:	e8 df 81 84 00       	call   0x848209
  2a:*	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)		<-- trapping instruction
  30:	72 11                	jb     0x43
  32:	48 83 c4 10          	add    $0x10,%rsp
  36:	31 c0                	xor    %eax,%eax
  38:	5b                   	pop    %rbx
  39:	5d                   	pop    %rbp
  3a:	41 5c                	pop    %r12
  3c:	41 5d                	pop    %r13
  3e:	41 5e                	pop    %r14

Code starting with the faulting instruction
===========================================
   0:	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)
   6:	72 11                	jb     0x19
   8:	48 83 c4 10          	add    $0x10,%rsp
   c:	31 c0                	xor    %eax,%eax
   e:	5b                   	pop    %rbx
   f:	5d                   	pop    %rbp
  10:	41 5c                	pop    %r12
  12:	41 5d                	pop    %r13
  14:	41 5e                	pop    %r14
[  131.315927][   T71] RSP: 0018:ffffc900004c7690 EFLAGS: 00010046
[  131.316135][   T71] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8a640aaa
[  131.316480][   T71] RDX: fffffbfff1d0fecd RSI: 0000000000000008 RDI: ffffffff8e87f660
[  131.316730][   T71] RBP: ffffc900004c76f8 R08: 0000000000000001 R09: fffffbfff1d0fecc
[  131.316969][   T71] R10: ffffffff8e87f667 R11: ffffc900004c7180 R12: 0000000000000000
[  131.317297][   T71] R13: 0000000000000286 R14: ffff888006109000 R15: dffffc0000000000
[  131.317536][   T71] FS:  0000000000000000(0000) GS:ffff8880a79ec000(0000) knlGS:0000000000000000
[  131.317914][   T71] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  131.318121][   T71] CR2: 0000000000000000 CR3: 0000000012535004 CR4: 0000000000772ef0
[  131.318362][   T71] PKRU: 55555554
[  131.318489][   T71] Call Trace:
[  131.318615][   T71]  <TASK>
[  131.318700][   T71]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  131.318863][   T71]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  131.319033][   T71]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  131.319195][   T71]  __cancel_work_sync (kernel/workqueue.c:4383)
[  131.319357][   T71]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  131.319516][   T71]  ? netdev_notify_peers (net/core/dev.c:1891)
[  131.319675][   T71]  ? netif_close_many (net/core/dev.c:1959)
[  131.319932][   T71]  netif_close_many (net/core/dev.c:1959)
[  131.320087][   T71]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  131.320248][   T71]  ? __dev_close_many (net/core/dev.c:1949)
[  131.320406][   T71]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  131.320698][   T71]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  131.320896][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  131.321052][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  131.321210][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  131.321364][   T71]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  131.321563][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  131.321722][   T71]  default_device_exit_batch (net/core/dev.c:13229)
[  131.321880][   T71]  ? unregister_netdev (net/core/dev.c:13204)
[  131.322038][   T71]  ops_undo_list (net/core/net_namespace.c:251)
[  131.322200][   T71]  ? netns_get (net/core/net_namespace.c:223)
[  131.322359][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  131.322522][   T71]  cleanup_net (net/core/net_namespace.c:698)
[  131.322682][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[  131.322848][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  131.323013][   T71]  process_one_work (kernel/workqueue.c:3268)
[  131.323177][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  131.323336][   T71]  ? assign_work (kernel/workqueue.c:1206)
[  131.323498][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  131.323655][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[  131.323811][   T71]  kthread (kernel/kthread.c:463)
[  131.323934][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  131.324096][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  131.324258][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  131.324420][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  131.324574][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  131.324736][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[  131.324904][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
kasan_report:kasan_check_range:try_to_grab_pending:__cancel_work:__cancel_work_sync
try_to_grab_pending:__cancel_work:__cancel_work_sync:__dev_close_many:netif_close_many