======================================
| [  374.941549][   T70] ==================================================================
| [  374.941901][   T70] 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)
| [  374.942198][   T70] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/70
| [  374.942500][   T70]
[  374.942607][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  374.942611][   T70] Workqueue: netns cleanup_net
[  374.942628][   T70] Call Trace:
[  374.942633][   T70]  <TASK>
[  374.942635][   T70]  dump_stack_lvl (lib/dump_stack.c:123)
[  374.942651][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  374.942655][   T70]  kasan_report (mm/kasan/report.c:597)
[  374.942667][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  374.942679][   T70]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[  374.942686][   T70]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  374.942693][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  374.942698][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  374.942706][   T70]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  374.942720][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[  374.942724][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  374.942737][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[  374.942744][   T70]  ? __mutex_lock (./arch/x86/include/asm/preempt.h:104 kernel/locking/mutex.c:739 kernel/locking/mutex.c:760)
[  374.942764][   T70]  netif_close_many (net/core/dev.c:1959)
[  374.942769][   T70]  ? ww_mutex_lock (kernel/locking/mutex.c:759)
[  374.942772][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[  374.942777][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  374.942788][   T70]  netif_close_many_and_unlock (net/core/dev.c:12476)
[  374.942793][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12539)
[  374.942797][   T70]  ? kasan_quarantine_put (mm/kasan/quarantine.c:234 (discriminator 1))
[  374.942802][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[  374.942806][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  374.942809][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  374.942812][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  374.942814][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  374.942817][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  374.942824][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[  374.942828][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[  374.942833][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[  374.942838][   T70]  ? netns_get (net/core/net_namespace.c:223)
[  374.942841][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  374.942847][   T70]  cleanup_net (net/core/net_namespace.c:698)
[  374.942851][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[  374.942855][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  374.942861][   T70]  process_one_work (kernel/workqueue.c:3268)
[  374.942868][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  374.942874][   T70]  ? assign_work (kernel/workqueue.c:1206)
[  374.942878][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  374.942885][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[  374.942889][   T70]  kthread (kernel/kthread.c:463)
[  374.942895][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  374.942898][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  374.942914][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  374.942920][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  374.942922][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  374.942926][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[  374.942929][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  374.942932][   T70]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  374.953303][   T70] #PF: error_code(0x0002) - not-present page
| [  374.953548][   T70] PGD 0 P4D 0
| [  374.953695][   T70] Oops: Oops: 0002 [#1] SMP KASAN
| [  374.954254][   T70] Tainted: [B]=BAD_PAGE
[  374.954408][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  374.954621][   T70] Workqueue: netns cleanup_net
[  374.954818][   T70] 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)
[  374.955033][   T70] 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 af 80 81 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 af 80 81 00       	call   0x8180d9
  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
[  374.955641][   T70] RSP: 0018:ffffc900004b7630 EFLAGS: 00010046
[  374.955875][   T70] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffb383e90a
[  374.956125][   T70] RDX: fffffbfff6f4decd RSI: 0000000000000008 RDI: ffffffffb7a6f660
[  374.956389][   T70] RBP: ffffc900004b7698 R08: 0000000000000001 R09: fffffbfff6f4decc
[  374.956652][   T70] R10: ffffffffb7a6f667 R11: ffffc900004b7100 R12: 0000000000000000
[  374.956921][   T70] R13: 0000000000000286 R14: ffff88800bec4000 R15: dffffc0000000000
[  374.957171][   T70] FS:  0000000000000000(0000) GS:ffff88807e97c000(0000) knlGS:0000000000000000
[  374.957482][   T70] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  374.957699][   T70] CR2: 0000000000000000 CR3: 0000000021f35006 CR4: 0000000000772ef0
[  374.957962][   T70] PKRU: 55555554
[  374.958095][   T70] Call Trace:
[  374.958230][   T70]  <TASK>
[  374.958331][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  374.958503][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  374.958670][   T70]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  374.958862][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[  374.959030][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  374.959198][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[  374.959371][   T70]  ? __mutex_lock (./arch/x86/include/asm/preempt.h:104 kernel/locking/mutex.c:739 kernel/locking/mutex.c:760)
[  374.959540][   T70]  netif_close_many (net/core/dev.c:1959)
[  374.959723][   T70]  ? ww_mutex_lock (kernel/locking/mutex.c:759)
[  374.959900][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[  374.960061][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  374.960235][   T70]  netif_close_many_and_unlock (net/core/dev.c:12476)
[  374.960417][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12539)
[  374.960620][   T70]  ? kasan_quarantine_put (mm/kasan/quarantine.c:234 (discriminator 1))
[  374.960816][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[  374.960985][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  374.961147][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  374.961331][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  374.961497][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  374.961722][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  374.961897][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[  374.962062][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[  374.962229][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[  374.962410][   T70]  ? netns_get (net/core/net_namespace.c:223)
[  374.962574][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  374.962773][   T70]  cleanup_net (net/core/net_namespace.c:698)
[  374.962940][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[  374.963102][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  374.963270][   T70]  process_one_work (kernel/workqueue.c:3268)
[  374.963460][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  374.963625][   T70]  ? assign_work (kernel/workqueue.c:1206)
[  374.963816][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  374.963984][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[  374.964147][   T70]  kthread (kernel/kthread.c:463)
[  374.964282][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  374.964453][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  374.964619][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  374.964808][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  374.964973][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  374.965134][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[  374.965309][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)


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