======================================
| [   18.636259][   T67] ==================================================================
| [   18.636604][   T67] 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)
| [   18.636919][   T67] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/67
| [   18.637237][   T67]
[   18.637354][   T67] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   18.637358][   T67] Workqueue: netns cleanup_net
[   18.637369][   T67] Call Trace:
[   18.637371][   T67]  <TASK>
[   18.637376][   T67]  dump_stack_lvl (lib/dump_stack.c:123)
[   18.637384][   T67]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   18.637388][   T67]  kasan_report (mm/kasan/report.c:597)
[   18.637401][   T67]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   18.637406][   T67]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   18.637410][   T67]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   18.637414][   T67]  ? netif_close_many (net/core/dev.c:1959)
[   18.637419][   T67]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   18.637423][   T67]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   18.637428][   T67]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   18.637433][   T67]  __cancel_work_sync (kernel/workqueue.c:4383)
[   18.637437][   T67]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   18.637441][   T67]  ? netdev_notify_peers (net/core/dev.c:1891)
[   18.637445][   T67]  ? netif_close_many (net/core/dev.c:1959)
[   18.637449][   T67]  netif_close_many (net/core/dev.c:1959)
[   18.637452][   T67]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   18.637458][   T67]  ? __dev_close_many (net/core/dev.c:1949)
[   18.637462][   T67]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   18.637465][   T67]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   18.637469][   T67]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   18.637473][   T67]  ? default_device_exit_batch (net/core/dev.c:13215)
[   18.637478][   T67]  ? 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)
[   18.637482][   T67]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   18.637485][   T67]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   18.637489][   T67]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   18.637492][   T67]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   18.637496][   T67]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   18.637502][   T67]  default_device_exit_batch (net/core/dev.c:13229)
[   18.637505][   T67]  ? unregister_netdev (net/core/dev.c:13204)
[   18.637511][   T67]  ops_undo_list (net/core/net_namespace.c:251)
[   18.637518][   T67]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   18.637521][   T67]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   18.637527][   T67]  cleanup_net (net/core/net_namespace.c:698)
[   18.637531][   T67]  ? net_passive_dec (net/core/net_namespace.c:660)
[   18.637536][   T67]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.637544][   T67]  process_one_work (kernel/workqueue.c:3268)
[   18.637550][   T67]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   18.637556][   T67]  ? assign_work (kernel/workqueue.c:1206)
[   18.637560][   T67]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   18.637566][   T67]  ? rescuer_thread (kernel/workqueue.c:3373)
[   18.637570][   T67]  kthread (kernel/kthread.c:463)
[   18.637576][   T67]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.637579][   T67]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   18.637584][   T67]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   18.637588][   T67]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.637591][   T67]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.637595][   T67]  ret_from_fork (arch/x86/kernel/process.c:164)
[   18.637597][   T67]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.637600][   T67]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   18.649428][   T67] #PF: error_code(0x0002) - not-present page
| [   18.649666][   T67] PGD 0 P4D 0
| [   18.649819][   T67] Oops: Oops: 0002 [#1] SMP KASAN
| [   18.650453][   T67] Tainted: [B]=BAD_PAGE
[   18.650597][   T67] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   18.650844][   T67] Workqueue: netns cleanup_net
[   18.651064][   T67] 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)
[   18.651337][   T67] 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
[   18.652017][   T67] RSP: 0018:ffffc90000487680 EFLAGS: 00010046
[   18.652263][   T67] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff9b849b8a
[   18.652545][   T67] RDX: fffffbfff40acacd RSI: 0000000000000008 RDI: ffffffffa0565660
[   18.652838][   T67] RBP: ffffc900004876e8 R08: 0000000000000001 R09: fffffbfff40acacc
[   18.653150][   T67] R10: ffffffffa0565667 R11: ffffc90000487140 R12: 0000000000000000
[   18.653431][   T67] R13: 0000000000000282 R14: ffff888007229000 R15: dffffc0000000000
[   18.653709][   T67] FS:  0000000000000000(0000) GS:ffff8880ccb07000(0000) knlGS:0000000000000000
[   18.654045][   T67] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   18.654300][   T67] CR2: 0000000000000000 CR3: 000000001bd49003 CR4: 0000000000772ef0
[   18.654578][   T67] PKRU: 55555554
[   18.654714][   T67] Call Trace:
[   18.654863][   T67]  <TASK>
[   18.654979][   T67]  ? netif_close_many (net/core/dev.c:1959)
[   18.655178][   T67]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   18.655368][   T67]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   18.655562][   T67]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   18.655751][   T67]  __cancel_work_sync (kernel/workqueue.c:4383)
[   18.655936][   T67]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   18.656125][   T67]  ? netdev_notify_peers (net/core/dev.c:1891)
[   18.656318][   T67]  ? netif_close_many (net/core/dev.c:1959)
[   18.656506][   T67]  netif_close_many (net/core/dev.c:1959)
[   18.656689][   T67]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   18.656872][   T67]  ? __dev_close_many (net/core/dev.c:1949)
[   18.657065][   T67]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   18.657303][   T67]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   18.657492][   T67]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   18.657723][   T67]  ? default_device_exit_batch (net/core/dev.c:13215)
[   18.657920][   T67]  ? 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)
[   18.658113][   T67]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   18.658309][   T67]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   18.658497][   T67]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   18.658723][   T67]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   18.658909][   T67]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   18.659100][   T67]  default_device_exit_batch (net/core/dev.c:13229)
[   18.659290][   T67]  ? unregister_netdev (net/core/dev.c:13204)
[   18.659478][   T67]  ops_undo_list (net/core/net_namespace.c:251)
[   18.659682][   T67]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   18.659866][   T67]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   18.660151][   T67]  cleanup_net (net/core/net_namespace.c:698)
[   18.660340][   T67]  ? net_passive_dec (net/core/net_namespace.c:660)
[   18.660525][   T67]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.660708][   T67]  process_one_work (kernel/workqueue.c:3268)
[   18.661042][   T67]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   18.661264][   T67]  ? assign_work (kernel/workqueue.c:1206)
[   18.661488][   T67]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   18.661688][   T67]  ? rescuer_thread (kernel/workqueue.c:3373)
[   18.662005][   T67]  kthread (kernel/kthread.c:463)
[   18.662177][   T67]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.662367][   T67]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   18.662565][   T67]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   18.662873][   T67]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.663059][   T67]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.663256][   T67]  ret_from_fork (arch/x86/kernel/process.c:164)
[   18.663488][   T67]  ? 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