======================================
| [   24.876021][   T68] ==================================================================
| [   24.876406][   T68] 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)
| [   24.876701][   T68] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/68
| [   24.876984][   T68]
[   24.877095][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   24.877100][   T68] Workqueue: netns cleanup_net
[   24.877111][   T68] Call Trace:
[   24.877113][   T68]  <TASK>
[   24.877117][   T68]  dump_stack_lvl (lib/dump_stack.c:123)
[   24.877128][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   24.877131][   T68]  kasan_report (mm/kasan/report.c:597)
[   24.877140][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   24.877146][   T68]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   24.877150][   T68]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   24.877155][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   24.877158][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   24.877163][   T68]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   24.877173][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   24.877178][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   24.877183][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   24.877187][   T68]  ? __mutex_lock (./arch/x86/include/asm/preempt.h:104 kernel/locking/mutex.c:739 kernel/locking/mutex.c:760)
[   24.877196][   T68]  netif_close_many (net/core/dev.c:1959)
[   24.877200][   T68]  ? ww_mutex_lock (kernel/locking/mutex.c:759)
[   24.877204][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   24.877207][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   24.877216][   T68]  netif_close_many_and_unlock (net/core/dev.c:12476)
[   24.877220][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12539)
[   24.877225][   T68]  ? default_device_exit_batch (net/core/dev.c:13215)
[   24.877230][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   24.877235][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   24.877238][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   24.877240][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   24.877244][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   24.877250][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   24.877254][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   24.877260][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   24.877266][   T68]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   24.877269][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   24.877275][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   24.877280][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   24.877284][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   24.877291][   T68]  process_one_work (kernel/workqueue.c:3268)
[   24.877298][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   24.877303][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   24.877308][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   24.877314][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   24.877318][   T68]  kthread (kernel/kthread.c:463)
[   24.877322][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   24.877325][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   24.877332][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   24.877337][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   24.877340][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   24.877345][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   24.877348][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   24.877353][   T68]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   24.888360][   T68] #PF: error_code(0x0002) - not-present page
| [   24.888593][   T68] PGD 0 P4D 0
| [   24.888744][   T68] Oops: Oops: 0002 [#1] SMP KASAN
| [   24.889365][   T68] Tainted: [B]=BAD_PAGE
[   24.889510][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   24.889749][   T68] Workqueue: netns cleanup_net
[   24.889951][   T68] 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)
[   24.890207][   T68] 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
[   24.890882][   T68] RSP: 0018:ffffc90000497630 EFLAGS: 00010046
[   24.891127][   T68] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffa6e49b8a
[   24.891413][   T68] RDX: fffffbfff576cacd RSI: 0000000000000008 RDI: ffffffffabb65660
[   24.891701][   T68] RBP: ffffc90000497698 R08: 0000000000000001 R09: fffffbfff576cacc
[   24.891981][   T68] R10: ffffffffabb65667 R11: ffffc90000497100 R12: 0000000000000000
[   24.892266][   T68] R13: 0000000000000286 R14: ffff88800bdfc000 R15: dffffc0000000000
[   24.892550][   T68] FS:  0000000000000000(0000) GS:ffff8880bb107000(0000) knlGS:0000000000000000
[   24.892888][   T68] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   24.893146][   T68] CR2: 0000000000000000 CR3: 0000000073b49003 CR4: 0000000000772ef0
[   24.893444][   T68] PKRU: 55555554
[   24.893595][   T68] Call Trace:
[   24.893739][   T68]  <TASK>
[   24.893839][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   24.894030][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   24.894231][   T68]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   24.894439][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   24.894628][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   24.894817][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   24.895006][   T68]  ? __mutex_lock (./arch/x86/include/asm/preempt.h:104 kernel/locking/mutex.c:739 kernel/locking/mutex.c:760)
[   24.895206][   T68]  netif_close_many (net/core/dev.c:1959)
[   24.895402][   T68]  ? ww_mutex_lock (kernel/locking/mutex.c:759)
[   24.895696][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   24.895885][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   24.896075][   T68]  netif_close_many_and_unlock (net/core/dev.c:12476)
[   24.896273][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12539)
[   24.896608][   T68]  ? default_device_exit_batch (net/core/dev.c:13215)
[   24.896792][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   24.896976][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   24.897190][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   24.897499][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   24.897728][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   24.897933][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   24.898123][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   24.898315][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   24.898504][   T68]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   24.898693][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   24.898883][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   24.899171][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   24.899367][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   24.899560][   T68]  process_one_work (kernel/workqueue.c:3268)
[   24.899748][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   24.899935][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   24.900122][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   24.900314][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   24.900506][   T68]  kthread (kernel/kthread.c:463)
[   24.900750][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   24.900939][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   24.901131][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   24.901321][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   24.901608][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   24.901795][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   24.901986][   T68]  ? 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