======================================
| [   19.634655][   T68] ==================================================================
| [   19.634990][   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)
| [   19.635282][   T68] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/68
| [   19.635557][   T68]
[   19.635664][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.635667][   T68] Workqueue: netns cleanup_net
[   19.635679][   T68] Call Trace:
[   19.635681][   T68]  <TASK>
[   19.635684][   T68]  dump_stack_lvl (lib/dump_stack.c:123)
[   19.635692][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.635696][   T68]  kasan_report (mm/kasan/report.c:597)
[   19.635704][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.635710][   T68]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   19.635714][   T68]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.635717][   T68]  ? irqentry_exit (kernel/entry/common.c:215)
[   19.635725][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.635728][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.635734][   T68]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   19.635739][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.635743][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.635749][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.635753][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   19.635757][   T68]  netif_close_many (net/core/dev.c:1959)
[   19.635760][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   19.635766][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   19.635769][   T68]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.635772][   T68]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   19.635777][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.635781][   T68]  ? default_device_exit_batch (net/core/dev.c:13215)
[   19.635786][   T68]  ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3189 kernel/locking/mutex.h:47 kernel/locking/mutex.c:67)
[   19.635789][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.635792][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.635797][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.635799][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.635803][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.635809][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   19.635813][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   19.635819][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   19.635824][   T68]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.635828][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.635834][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   19.635838][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.635843][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.635850][   T68]  process_one_work (kernel/workqueue.c:3268)
[   19.635857][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.635863][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   19.635871][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.635880][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.635885][   T68]  kthread (kernel/kthread.c:463)
[   19.635889][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.635892][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.635896][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.635900][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.635903][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.635907][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.635909][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.635912][   T68]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   19.647189][   T68] #PF: error_code(0x0002) - not-present page
| [   19.647419][   T68] PGD 0 P4D 0
| [   19.647564][   T68] Oops: Oops: 0002 [#1] SMP KASAN
| [   19.648182][   T68] Tainted: [B]=BAD_PAGE
[   19.648325][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.648556][   T68] Workqueue: netns cleanup_net
[   19.648765][   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)
[   19.649023][   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
[   19.649690][   T68] RSP: 0018:ffffc90000497680 EFLAGS: 00010046
[   19.649927][   T68] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8c049b8a
[   19.650202][   T68] RDX: fffffbfff21acacd RSI: 0000000000000008 RDI: ffffffff90d65660
[   19.650475][   T68] RBP: ffffc900004976e8 R08: 0000000000000001 R09: fffffbfff21acacc
[   19.650746][   T68] R10: ffffffff90d65667 R11: ffffc90000497140 R12: 0000000000000000
[   19.651032][   T68] R13: 0000000000000282 R14: ffff88800f469000 R15: dffffc0000000000
[   19.651298][   T68] FS:  0000000000000000(0000) GS:ffff8880dc387000(0000) knlGS:0000000000000000
[   19.651618][   T68] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   19.651857][   T68] CR2: 0000000000000000 CR3: 0000000036f49006 CR4: 0000000000772ef0
[   19.652144][   T68] PKRU: 55555554
[   19.652281][   T68] Call Trace:
[   19.652418][   T68]  <TASK>
[   19.652515][   T68]  ? irqentry_exit (kernel/entry/common.c:215)
[   19.652708][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.652898][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.653085][   T68]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   19.653267][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.653458][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.653661][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.653844][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   19.654042][   T68]  netif_close_many (net/core/dev.c:1959)
[   19.654228][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   19.654417][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   19.654597][   T68]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.654828][   T68]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   19.655042][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.655271][   T68]  ? default_device_exit_batch (net/core/dev.c:13215)
[   19.655471][   T68]  ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3189 kernel/locking/mutex.h:47 kernel/locking/mutex.c:67)
[   19.655640][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.655806][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.656003][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.656224][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.656412][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.656592][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   19.656780][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   19.656969][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   19.657154][   T68]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.657330][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.657516][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   19.657700][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.657884][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.658065][   T68]  process_one_work (kernel/workqueue.c:3268)
[   19.658246][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.658431][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   19.658613][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.658802][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.658994][   T68]  kthread (kernel/kthread.c:463)
[   19.659134][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.659316][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.659505][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.659696][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.659883][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.660069][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.660249][   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