======================================
| [   23.904521][   T71] ==================================================================
| [   23.904843][   T71] 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)
| [   23.905130][   T71] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/71
| [   23.905435][   T71]
[   23.905550][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   23.905553][   T71] Workqueue: netns cleanup_net
[   23.905565][   T71] Call Trace:
[   23.905569][   T71]  <TASK>
[   23.905572][   T71]  dump_stack_lvl (lib/dump_stack.c:123)
[   23.905580][   T71]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   23.905584][   T71]  kasan_report (mm/kasan/report.c:597)
[   23.905592][   T71]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   23.905598][   T71]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   23.905603][   T71]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   23.905611][   T71]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   23.905616][   T71]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   23.905623][   T71]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   23.905628][   T71]  __cancel_work_sync (kernel/workqueue.c:4383)
[   23.905632][   T71]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   23.905638][   T71]  ? netdev_notify_peers (net/core/dev.c:1891)
[   23.905642][   T71]  ? netif_close_many (net/core/dev.c:1959)
[   23.905646][   T71]  netif_close_many (net/core/dev.c:1959)
[   23.905649][   T71]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   23.905656][   T71]  ? __dev_close_many (net/core/dev.c:1949)
[   23.905659][   T71]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   23.905662][   T71]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   23.905667][   T71]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   23.905671][   T71]  ? default_device_exit_batch (net/core/dev.c:13215)
[   23.905676][   T71]  ? 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)
[   23.905680][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   23.905683][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   23.905688][   T71]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   23.905691][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   23.905694][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   23.905700][   T71]  default_device_exit_batch (net/core/dev.c:13229)
[   23.905704][   T71]  ? unregister_netdev (net/core/dev.c:13204)
[   23.905710][   T71]  ops_undo_list (net/core/net_namespace.c:251)
[   23.905716][   T71]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   23.905719][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   23.905725][   T71]  cleanup_net (net/core/net_namespace.c:698)
[   23.905729][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[   23.905734][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   23.905744][   T71]  process_one_work (kernel/workqueue.c:3268)
[   23.905751][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   23.905756][   T71]  ? assign_work (kernel/workqueue.c:1206)
[   23.905761][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   23.905767][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[   23.905770][   T71]  kthread (kernel/kthread.c:463)
[   23.905776][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   23.905779][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   23.905786][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   23.905790][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   23.905793][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   23.905797][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[   23.905800][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   23.905803][   T71]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   23.916347][   T71] #PF: error_code(0x0002) - not-present page
| [   23.916552][   T71] PGD 0 P4D 0
| [   23.916683][   T71] Oops: Oops: 0002 [#1] SMP KASAN
| [   23.917353][   T71] Tainted: [B]=BAD_PAGE
[   23.917484][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   23.917697][   T71] Workqueue: netns cleanup_net
[   23.917973][   T71] 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)
[   23.918193][   T71] 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
[   23.918902][   T71] RSP: 0018:ffffc900004c7680 EFLAGS: 00010046
[   23.919129][   T71] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffb8a49b8a
[   23.919486][   T71] RDX: fffffbfff7aecacd RSI: 0000000000000008 RDI: ffffffffbd765660
[   23.919762][   T71] RBP: ffffc900004c76e8 R08: 0000000000000001 R09: fffffbfff7aecacc
[   23.920007][   T71] R10: ffffffffbd765667 R11: ffffc900004c7140 R12: 0000000000000000
[   23.920376][   T71] R13: 0000000000000282 R14: ffff88800b914000 R15: dffffc0000000000
[   23.920630][   T71] FS:  0000000000000000(0000) GS:ffff8880a9587000(0000) knlGS:0000000000000000
[   23.921007][   T71] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   23.921222][   T71] CR2: 0000000000000000 CR3: 000000006b349002 CR4: 0000000000772ef0
[   23.921474][   T71] PKRU: 55555554
[   23.921617][   T71] Call Trace:
[   23.921838][   T71]  <TASK>
[   23.921934][   T71]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   23.922110][   T71]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   23.922281][   T71]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   23.922446][   T71]  __cancel_work_sync (kernel/workqueue.c:4383)
[   23.922705][   T71]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   23.922869][   T71]  ? netdev_notify_peers (net/core/dev.c:1891)
[   23.923064][   T71]  ? netif_close_many (net/core/dev.c:1959)
[   23.923239][   T71]  netif_close_many (net/core/dev.c:1959)
[   23.923497][   T71]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   23.923664][   T71]  ? __dev_close_many (net/core/dev.c:1949)
[   23.923825][   T71]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   23.924161][   T71]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   23.924340][   T71]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   23.924609][   T71]  ? default_device_exit_batch (net/core/dev.c:13215)
[   23.924785][   T71]  ? 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)
[   23.925048][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   23.925232][   T71]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   23.925424][   T71]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   23.925634][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   23.925902][   T71]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   23.926088][   T71]  default_device_exit_batch (net/core/dev.c:13229)
[   23.926272][   T71]  ? unregister_netdev (net/core/dev.c:13204)
[   23.926436][   T71]  ops_undo_list (net/core/net_namespace.c:251)
[   23.926699][   T71]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   23.926858][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   23.927023][   T71]  cleanup_net (net/core/net_namespace.c:698)
[   23.927184][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[   23.927438][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   23.927609][   T71]  process_one_work (kernel/workqueue.c:3268)
[   23.927776][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   23.927938][   T71]  ? assign_work (kernel/workqueue.c:1206)
[   23.928205][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   23.928371][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[   23.928539][   T71]  kthread (kernel/kthread.c:463)
[   23.928663][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   23.928915][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   23.929080][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   23.929261][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   23.929422][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   23.929692][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[   23.929856][   T71]  ? 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