======================================
| [   19.727969][   T70] ==================================================================
| [   19.728331][   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)
| [   19.728642][   T70] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/70
| [   19.728933][   T70]
[   19.729054][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.729057][   T70] Workqueue: netns cleanup_net
[   19.729066][   T70] Call Trace:
[   19.729068][   T70]  <TASK>
[   19.729071][   T70]  dump_stack_lvl (lib/dump_stack.c:123)
[   19.729077][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.729080][   T70]  kasan_report (mm/kasan/report.c:597)
[   19.729087][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.729096][   T70]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   19.729102][   T70]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.729109][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.729112][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.729121][   T70]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   19.729128][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.729134][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.729138][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.729142][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   19.729146][   T70]  netif_close_many (net/core/dev.c:1959)
[   19.729150][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   19.729155][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   19.729159][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.729162][   T70]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   19.729166][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.729170][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[   19.729175][   T70]  ? 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)
[   19.729178][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.729182][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.729185][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.729188][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.729191][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.729197][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   19.729201][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   19.729207][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   19.729212][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.729216][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.729222][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   19.729226][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.729231][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.729240][   T70]  process_one_work (kernel/workqueue.c:3268)
[   19.729246][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.729252][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   19.729257][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.729263][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.729266][   T70]  kthread (kernel/kthread.c:463)
[   19.729272][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.729274][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.729280][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.729284][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.729287][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.729291][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.729293][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.729296][   T70]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   19.740113][   T70] #PF: error_code(0x0002) - not-present page
| [   19.740337][   T70] PGD 0 P4D 0
| [   19.740472][   T70] Oops: Oops: 0002 [#1] SMP KASAN
| [   19.741084][   T70] Tainted: [B]=BAD_PAGE
[   19.741240][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.741461][   T70] Workqueue: netns cleanup_net
[   19.741653][   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)
[   19.741883][   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 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
[   19.742539][   T70] RSP: 0000:ffffc900004b7680 EFLAGS: 00010046
[   19.742765][   T70] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffaf849b8a
[   19.743140][   T70] RDX: fffffbfff68acacd RSI: 0000000000000008 RDI: ffffffffb4565660
[   19.743402][   T70] RBP: ffffc900004b76e8 R08: 0000000000000001 R09: fffffbfff68acacc
[   19.743666][   T70] R10: ffffffffb4565667 R11: ffffc900004b7140 R12: 0000000000000000
[   19.744031][   T70] R13: 0000000000000282 R14: ffff88800e609000 R15: dffffc0000000000
[   19.744309][   T70] FS:  0000000000000000(0000) GS:ffff8880b8b87000(0000) knlGS:0000000000000000
[   19.744712][   T70] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   19.744937][   T70] CR2: 0000000000000000 CR3: 000000004d749005 CR4: 0000000000772ef0
[   19.745223][   T70] PKRU: 55555554
[   19.745359][   T70] Call Trace:
[   19.745586][   T70]  <TASK>
[   19.745681][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.745862][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.746041][   T70]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   19.746229][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.746498][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.746681][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.746860][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   19.747060][   T70]  netif_close_many (net/core/dev.c:1959)
[   19.747340][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   19.747516][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   19.747693][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.748002][   T70]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   19.748194][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.748411][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[   19.748589][   T70]  ? 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)
[   19.748860][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.749035][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.749222][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.749439][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.749712][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.749887][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   19.750065][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   19.750254][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   19.750526][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.750700][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.750881][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   19.751059][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.751342][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.751522][   T70]  process_one_work (kernel/workqueue.c:3268)
[   19.751703][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.751881][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   19.752164][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.752341][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.752531][   T70]  kthread (kernel/kthread.c:463)
[   19.752683][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.752964][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.753167][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.753356][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.753544][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.753827][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.754016][   T70]  ? 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