======================================
| [   25.026805][   T70] ==================================================================
| [   25.027124][   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)
| [   25.027401][   T70] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/70
| [   25.027663][   T70]
[   25.027768][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   25.027770][   T70] Workqueue: netns cleanup_net
[   25.027778][   T70] Call Trace:
[   25.027780][   T70]  <TASK>
[   25.027782][   T70]  dump_stack_lvl (lib/dump_stack.c:123)
[   25.027789][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   25.027792][   T70]  kasan_report (mm/kasan/report.c:597)
[   25.027798][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   25.027804][   T70]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   25.027808][   T70]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   25.027813][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   25.027816][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   25.027821][   T70]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   25.027826][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   25.027830][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   25.027837][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   25.027841][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   25.027846][   T70]  netif_close_many (net/core/dev.c:1959)
[   25.027850][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   25.027855][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   25.027860][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   25.027865][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   25.027869][   T70]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   25.027873][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   25.027876][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   25.027879][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   25.027881][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   25.027883][   T70]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   25.027887][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   25.027893][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   25.027896][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   25.027902][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   25.027907][   T70]  ? netns_get (net/core/net_namespace.c:223)
[   25.027909][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   25.027915][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   25.027919][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   25.027923][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   25.027930][   T70]  process_one_work (kernel/workqueue.c:3268)
[   25.027937][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   25.027943][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   25.027947][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   25.027953][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   25.027957][   T70]  kthread (kernel/kthread.c:463)
[   25.027962][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   25.027965][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   25.027969][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   25.027972][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   25.027976][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   25.027980][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   25.027982][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   25.027985][   T70]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   25.038105][   T70] #PF: error_code(0x0002) - not-present page
| [   25.038318][   T70] PGD 0 P4D 0
| [   25.038455][   T70] Oops: Oops: 0002 [#1] SMP KASAN
| [   25.039008][   T70] Tainted: [B]=BAD_PAGE
[   25.039149][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   25.039368][   T70] Workqueue: netns cleanup_net
[   25.039553][   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)
[   25.039777][   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 6f 7d 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 6f 7d 81 00       	call   0x817d99
  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
[   25.040384][   T70] RSP: 0018:ffffc900004b7690 EFLAGS: 00010046
[   25.040609][   T70] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffb124190a
[   25.040867][   T70] RDX: fffffbfff6adcecd RSI: 0000000000000008 RDI: ffffffffb56e7660
[   25.041125][   T70] RBP: ffffc900004b76f8 R08: 0000000000000001 R09: fffffbfff6adcecc
[   25.041391][   T70] R10: ffffffffb56e7667 R11: ffffc900004b7180 R12: 0000000000000000
[   25.041652][   T70] R13: 0000000000000286 R14: ffff8880107bc000 R15: dffffc0000000000
[   25.041907][   T70] FS:  0000000000000000(0000) GS:ffff888080c04000(0000) knlGS:0000000000000000
[   25.042210][   T70] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   25.042430][   T70] CR2: 0000000000000000 CR3: 0000000004ba6003 CR4: 0000000000772ef0
[   25.042685][   T70] PKRU: 55555554
[   25.042817][   T70] Call Trace:
[   25.042945][   T70]  <TASK>
[   25.043031][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   25.043211][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   25.043389][   T70]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   25.043562][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   25.043738][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   25.043902][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   25.044069][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   25.044245][   T70]  netif_close_many (net/core/dev.c:1959)
[   25.044424][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   25.044595][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   25.044787][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   25.044995][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   25.045209][   T70]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   25.045376][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   25.045551][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   25.045724][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   25.045887][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   25.046123][   T70]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   25.046297][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   25.046475][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   25.046644][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   25.046821][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   25.046993][   T70]  ? netns_get (net/core/net_namespace.c:223)
[   25.047164][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   25.047352][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   25.047534][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   25.047707][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   25.047875][   T70]  process_one_work (kernel/workqueue.c:3268)
[   25.048042][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   25.048221][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   25.048388][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   25.048662][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   25.048844][   T70]  kthread (kernel/kthread.c:463)
[   25.048968][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   25.049140][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   25.049415][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   25.049597][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   25.049770][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   25.049937][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   25.050209][   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