======================================
| [   19.640290][   T12] ==================================================================
| [   19.640624][   T12] 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)
| [   19.640927][   T12] Write of size 8 at addr 0000000000000000 by task kworker/u16:0/12
| [   19.641220][   T12]
[   19.641334][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.641336][   T12] Workqueue: netns cleanup_net
[   19.641348][   T12] Call Trace:
[   19.641351][   T12]  <TASK>
[   19.641353][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[   19.641362][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.641365][   T12]  kasan_report (mm/kasan/report.c:597)
[   19.641373][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.641379][   T12]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   19.641383][   T12]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.641388][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.641392][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.641399][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.641403][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.641409][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.641412][   T12]  ? netif_close_many (net/core/dev.c:1959)
[   19.641417][   T12]  netif_close_many (net/core/dev.c:1959)
[   19.641420][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.641424][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.641428][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[   19.641432][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.641437][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.641440][   T12]  ? vxlan_dellink (drivers/net/vxlan/vxlan_core.c:4488) vxlan
[   19.641456][   T12]  ? vxlan_fdb_delete_bulk (drivers/net/vxlan/vxlan_core.c:4480) vxlan
[   19.641471][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.641479][   T12]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[   19.641484][   T12]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.641488][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.641494][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   19.641498][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.641503][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.641511][   T12]  process_one_work (kernel/workqueue.c:3268)
[   19.641517][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.641523][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   19.641528][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.641534][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.641538][   T12]  kthread (kernel/kthread.c:463)
[   19.641542][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.641545][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.641549][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.641554][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.641557][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.641561][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.641563][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.641566][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   19.651687][   T12] #PF: error_code(0x0002) - not-present page
| [   19.651914][   T12] PGD 0 P4D 0
| [   19.652066][   T12] Oops: Oops: 0002 [#1] SMP KASAN
| [   19.652698][   T12] Tainted: [B]=BAD_PAGE
[   19.652843][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.653082][   T12] Workqueue: netns cleanup_net
[   19.653295][   T12] 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)
[   19.653541][   T12] 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 1f 93 82 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 1f 93 82 00       	call   0x829349
  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
[   19.654206][   T12] RSP: 0018:ffffc900000c7720 EFLAGS: 00010046
[   19.654452][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffaf849b8a
[   19.654743][   T12] RDX: fffffbfff68acacd RSI: 0000000000000008 RDI: ffffffffb4565660
[   19.655028][   T12] RBP: ffffc900000c7788 R08: 0000000000000001 R09: fffffbfff68acacc
[   19.655317][   T12] R10: ffffffffb4565667 R11: ffffc900000c7200 R12: 0000000000000000
[   19.655597][   T12] R13: 0000000000000282 R14: ffff8880094a2000 R15: dffffc0000000000
[   19.655882][   T12] FS:  0000000000000000(0000) GS:ffff8880b8c87000(0000) knlGS:0000000000000000
[   19.656214][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   19.656461][   T12] CR2: 0000000000000000 CR3: 0000000042b49002 CR4: 0000000000772ef0
[   19.656740][   T12] PKRU: 55555554
[   19.656884][   T12] Call Trace:
[   19.657030][   T12]  <TASK>
[   19.657130][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.657329][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.657522][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.657711][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.657901][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.658089][   T12]  ? netif_close_many (net/core/dev.c:1959)
[   19.658285][   T12]  netif_close_many (net/core/dev.c:1959)
[   19.658480][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.658670][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.658904][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[   19.659091][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.659330][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.659566][   T12]  ? vxlan_dellink (drivers/net/vxlan/vxlan_core.c:4488) vxlan
[   19.659782][   T12]  ? vxlan_fdb_delete_bulk (drivers/net/vxlan/vxlan_core.c:4480) vxlan
[   19.660032][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.660225][   T12]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[   19.660420][   T12]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.660610][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.660797][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   19.660986][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.661175][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.661378][   T12]  process_one_work (kernel/workqueue.c:3268)
[   19.661570][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.661762][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   19.661951][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.662144][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.662336][   T12]  kthread (kernel/kthread.c:463)
[   19.662483][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.662671][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.662864][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.663052][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.663243][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.663432][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.663619][   T12]  ? 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