======================================
| [   20.442164][   T69] ==================================================================
| [   20.442656][   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)
| [   20.443106][   T69] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/69
| [   20.443552][   T69]
[   20.443720][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   20.443726][   T69] Workqueue: netns cleanup_net
[   20.443740][   T69] Call Trace:
[   20.443743][   T69]  <TASK>
[   20.443747][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   20.443758][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   20.443774][   T69]  kasan_report (mm/kasan/report.c:597)
[   20.443785][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   20.443795][   T69]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   20.443802][   T69]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   20.443811][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   20.443817][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   20.443829][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   20.443841][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   20.443848][   T69]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   20.443857][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   20.443864][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   20.443872][   T69]  netif_close_many (net/core/dev.c:1959)
[   20.443879][   T69]  ? _mutex_trylock_nest_lock (kernel/locking/mutex.c:916)
[   20.443890][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   20.443897][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   20.443906][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   20.443915][   T69]  ? trace_sched_stat_iowait (kernel/sched/wait.c:402)
[   20.443923][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   20.443939][   T69]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[   20.443950][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   20.443955][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   20.443967][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   20.443975][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   20.443983][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   20.443994][   T69]  process_one_work (kernel/workqueue.c:3268)
[   20.444007][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   20.444018][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   20.444027][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   20.444039][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   20.444046][   T69]  kthread (kernel/kthread.c:463)
[   20.444054][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   20.444059][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   20.444066][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   20.444073][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   20.444079][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   20.444086][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   20.444091][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   20.444096][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   20.458674][   T69] #PF: error_code(0x0002) - not-present page
| [   20.459012][   T69] PGD 0 P4D 0
| [   20.459237][   T69] Oops: Oops: 0002 [#1] SMP KASAN
| [   20.460135][   T69] Tainted: [B]=BAD_PAGE
[   20.460338][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   20.460660][   T69] Workqueue: netns cleanup_net
[   20.460953][   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)
[   20.461318][   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
[   20.462297][   T69] RSP: 0018:ffffc900004a7720 EFLAGS: 00010046
[   20.462642][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffaca49b8a
[   20.463054][   T69] RDX: fffffbfff62ecacd RSI: 0000000000000008 RDI: ffffffffb1765660
[   20.463461][   T69] RBP: ffffc900004a7788 R08: 0000000000000001 R09: fffffbfff62ecacc
[   20.463863][   T69] R10: ffffffffb1765667 R11: ffffc900004a7200 R12: 0000000000000000
[   20.464267][   T69] R13: 0000000000000282 R14: ffff8880097b2000 R15: dffffc0000000000
[   20.464683][   T69] FS:  0000000000000000(0000) GS:ffff8880bba07000(0000) knlGS:0000000000000000
[   20.465146][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   20.465482][   T69] CR2: 0000000000000000 CR3: 0000000039b49001 CR4: 0000000000772ef0
[   20.465874][   T69] PKRU: 55555554
[   20.466072][   T69] Call Trace:
[   20.466287][   T69]  <TASK>
[   20.466430][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   20.466712][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   20.466985][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   20.467256][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   20.467527][   T69]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   20.467801][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   20.468077][   T69]  ? netif_close_many (net/core/dev.c:1959)
[   20.468343][   T69]  netif_close_many (net/core/dev.c:1959)
[   20.468613][   T69]  ? _mutex_trylock_nest_lock (kernel/locking/mutex.c:916)
[   20.468890][   T69]  ? __dev_close_many (net/core/dev.c:1949)
[   20.469161][   T69]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   20.469498][   T69]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   20.469841][   T69]  ? trace_sched_stat_iowait (kernel/sched/wait.c:402)
[   20.470111][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   20.470381][   T69]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[   20.470656][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   20.470916][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   20.471183][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   20.471448][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   20.471724][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   20.471997][   T69]  process_one_work (kernel/workqueue.c:3268)
[   20.472271][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   20.472541][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   20.472820][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   20.473090][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   20.473373][   T69]  kthread (kernel/kthread.c:463)
[   20.473572][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   20.473837][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   20.474109][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   20.474380][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   20.474650][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   20.474926][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   20.475199][   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