======================================
| [  451.203022][   T69] ==================================================================
| [  451.203336][   T69] 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)
| [  451.203657][   T69] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/69
| [  451.203946][   T69]
[  451.204066][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  451.204072][   T69] Workqueue: netns cleanup_net
[  451.204090][   T69] Call Trace:
[  451.204093][   T69]  <TASK>
[  451.204097][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[  451.204109][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  451.204114][   T69]  kasan_report (mm/kasan/report.c:597)
[  451.204130][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  451.204136][   T69]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[  451.204140][   T69]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  451.204145][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  451.204149][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  451.204153][   T69]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  451.204164][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[  451.204169][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  451.204174][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[  451.204178][   T69]  ? netif_close_many (net/core/dev.c:1959)
[  451.204182][   T69]  netif_close_many (net/core/dev.c:1959)
[  451.204185][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  451.204192][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[  451.204195][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  451.204200][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  451.204204][   T69]  ? 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)
[  451.204207][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  451.204213][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  451.204217][   T69]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[  451.204228][   T69]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[  451.204234][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[  451.204237][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  451.204243][   T69]  cleanup_net (net/core/net_namespace.c:698)
[  451.204248][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[  451.204252][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  451.204260][   T69]  process_one_work (kernel/workqueue.c:3268)
[  451.204266][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  451.204272][   T69]  ? assign_work (kernel/workqueue.c:1206)
[  451.204277][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  451.204283][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[  451.204287][   T69]  kthread (kernel/kthread.c:463)
[  451.204292][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  451.204295][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  451.204302][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  451.204306][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  451.204309][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  451.204313][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[  451.204316][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  451.204319][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  451.214162][   T69] #PF: error_code(0x0002) - not-present page
| [  451.214369][   T69] PGD 0 P4D 0
| [  451.214518][   T69] Oops: Oops: 0002 [#1] SMP KASAN
| [  451.215241][   T69] Tainted: [B]=BAD_PAGE
[  451.215375][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  451.215694][   T69] Workqueue: netns cleanup_net
[  451.215882][   T69] 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)
[  451.216141][   T69] 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
[  451.216843][   T69] RSP: 0018:ffffc900004a7720 EFLAGS: 00010046
[  451.217074][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff99849b8a
[  451.217436][   T69] RDX: fffffbfff3cacacd RSI: 0000000000000008 RDI: ffffffff9e565660
[  451.217689][   T69] RBP: ffffc900004a7788 R08: 0000000000000001 R09: fffffbfff3cacacc
[  451.217942][   T69] R10: ffffffff9e565667 R11: ffffc900004a7200 R12: 0000000000000000
[  451.218329][   T69] R13: 0000000000000282 R14: ffff88800e071000 R15: dffffc0000000000
[  451.218594][   T69] FS:  0000000000000000(0000) GS:ffff8880c8807000(0000) knlGS:0000000000000000
[  451.218993][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  451.219213][   T69] CR2: 0000000000000000 CR3: 000000000b7a2005 CR4: 0000000000772ef0
[  451.219491][   T69] PKRU: 55555554
[  451.219623][   T69] Call Trace:
[  451.219857][   T69]  <TASK>
[  451.219946][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  451.220141][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  451.220314][   T69]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  451.220589][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[  451.220770][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  451.220942][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[  451.221111][   T69]  ? netif_close_many (net/core/dev.c:1959)
[  451.221379][   T69]  netif_close_many (net/core/dev.c:1959)
[  451.221566][   T69]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  451.221750][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[  451.221912][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  451.222221][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  451.222443][   T69]  ? 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)
[  451.222615][   T69]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  451.222789][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  451.223050][   T69]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[  451.223240][   T69]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[  451.223413][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[  451.223587][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  451.223860][   T69]  cleanup_net (net/core/net_namespace.c:698)
[  451.224024][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[  451.224202][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  451.224379][   T69]  process_one_work (kernel/workqueue.c:3268)
[  451.224665][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  451.224841][   T69]  ? assign_work (kernel/workqueue.c:1206)
[  451.225023][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  451.225184][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[  451.225458][   T69]  kthread (kernel/kthread.c:463)
[  451.225592][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  451.225763][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  451.225927][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  451.226186][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  451.226371][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  451.226552][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[  451.226727][   T69]  ? 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