======================================
| [   68.453124][   T68] ==================================================================
| [   68.453467][   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)
| [   68.453739][   T68] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/68
| [   68.454014][   T68]
[   68.454122][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   68.454127][   T68] Workqueue: netns cleanup_net
[   68.454138][   T68] Call Trace:
[   68.454143][   T68]  <TASK>
[   68.454145][   T68]  dump_stack_lvl (lib/dump_stack.c:123)
[   68.454154][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   68.454157][   T68]  kasan_report (mm/kasan/report.c:597)
[   68.454165][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   68.454171][   T68]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   68.454175][   T68]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   68.454180][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   68.454184][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   68.454189][   T68]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   68.454194][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   68.454198][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   68.454206][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   68.454211][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   68.454216][   T68]  netif_close_many (net/core/dev.c:1959)
[   68.454219][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   68.454227][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   68.454231][   T68]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   68.454236][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   68.454240][   T68]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   68.454244][   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)
[   68.454248][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   68.454251][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   68.454254][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   68.454257][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   68.454260][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   68.454266][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   68.454269][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   68.454275][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   68.454280][   T68]  ? netns_get (net/core/net_namespace.c:223)
[   68.454283][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   68.454289][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   68.454292][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   68.454297][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.454305][   T68]  process_one_work (kernel/workqueue.c:3268)
[   68.454312][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   68.454318][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   68.454323][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   68.454329][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   68.454333][   T68]  kthread (kernel/kthread.c:463)
[   68.454339][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.454342][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   68.454348][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   68.454352][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.454355][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.454359][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   68.454362][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.454365][   T68]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   68.465055][   T68] #PF: error_code(0x0002) - not-present page
| [   68.465359][   T68] PGD 0 P4D 0
| [   68.465493][   T68] Oops: Oops: 0002 [#1] SMP KASAN
| [   68.466151][   T68] Tainted: [B]=BAD_PAGE
[   68.466289][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   68.466500][   T68] Workqueue: netns cleanup_net
[   68.466680][   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)
[   68.466906][   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 6f 7d 81 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 6f 7d 81 00       	call   0x817d99
  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
[   68.467517][   T68] RSP: 0018:ffffc90000497690 EFLAGS: 00010046
[   68.467840][   T68] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffa1c4190a
[   68.468115][   T68] RDX: fffffbfff4c1cecd RSI: 0000000000000008 RDI: ffffffffa60e7660
[   68.468478][   T68] RBP: ffffc900004976f8 R08: 0000000000000001 R09: fffffbfff4c1cecc
[   68.468737][   T68] R10: ffffffffa60e7667 R11: ffffc90000497180 R12: 0000000000000000
[   68.469003][   T68] R13: 0000000000000286 R14: ffff88800b284000 R15: dffffc0000000000
[   68.469360][   T68] FS:  0000000000000000(0000) GS:ffff88808a404000(0000) knlGS:0000000000000000
[   68.469667][   T68] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   68.469885][   T68] CR2: 0000000000000000 CR3: 0000000037559003 CR4: 0000000000772ef0
[   68.470252][   T68] PKRU: 55555554
[   68.470386][   T68] Call Trace:
[   68.470515][   T68]  <TASK>
[   68.470613][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   68.470887][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   68.471065][   T68]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   68.471236][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   68.471411][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   68.471686][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   68.471858][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   68.472033][   T68]  netif_close_many (net/core/dev.c:1959)
[   68.472202][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   68.472467][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   68.472641][   T68]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   68.472852][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   68.473067][   T68]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   68.473337][   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)
[   68.473506][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   68.473674][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   68.473847][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   68.474154][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   68.474321][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   68.474492][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   68.474664][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   68.474936][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   68.475109][   T68]  ? netns_get (net/core/net_namespace.c:223)
[   68.475278][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   68.475449][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   68.475715][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   68.475883][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.476056][   T68]  process_one_work (kernel/workqueue.c:3268)
[   68.476232][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   68.476499][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   68.476667][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   68.476837][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   68.477012][   T68]  kthread (kernel/kthread.c:463)
[   68.477235][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.477401][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   68.477572][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   68.477747][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.477937][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.478108][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   68.478275][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
try_to_grab_pending:__cancel_work:__cancel_work_sync:__dev_close_many:netif_close_many
kasan_report:kasan_check_range:try_to_grab_pending:__cancel_work:__cancel_work_sync