======================================
| [   15.301144][   T68] ==================================================================
| [   15.301539][   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)
| [   15.301866][   T68] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/68
| [   15.302161][   T68]
[   15.302282][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   15.302286][   T68] Workqueue: netns cleanup_net
[   15.302294][   T68] Call Trace:
[   15.302297][   T68]  <TASK>
[   15.302299][   T68]  dump_stack_lvl (lib/dump_stack.c:123)
[   15.302307][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   15.302310][   T68]  kasan_report (mm/kasan/report.c:597)
[   15.302318][   T68]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   15.302323][   T68]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   15.302326][   T68]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   15.302329][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   15.302335][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   15.302338][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   15.302343][   T68]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   15.302347][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   15.302351][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   15.302355][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   15.302358][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   15.302363][   T68]  netif_close_many (net/core/dev.c:1959)
[   15.302366][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   15.302371][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   15.302374][   T68]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   15.302379][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   15.302384][   T68]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   15.302389][   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)
[   15.302392][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   15.302396][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   15.302399][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   15.302402][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   15.302406][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   15.302412][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   15.302416][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   15.302422][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   15.302426][   T68]  ? netns_get (net/core/net_namespace.c:223)
[   15.302428][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   15.302433][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   15.302437][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   15.302440][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.302447][   T68]  process_one_work (kernel/workqueue.c:3268)
[   15.302453][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   15.302458][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   15.302462][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   15.302468][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   15.302471][   T68]  kthread (kernel/kthread.c:463)
[   15.302475][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.302477][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   15.302485][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   15.302489][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.302492][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.302495][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   15.302498][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.302500][   T68]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   15.314353][   T68] #PF: error_code(0x0002) - not-present page
| [   15.314601][   T68] PGD 0 P4D 0
| [   15.314757][   T68] Oops: Oops: 0002 [#1] SMP KASAN
| [   15.315420][   T68] Tainted: [B]=BAD_PAGE
[   15.315570][   T68] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   15.315819][   T68] Workqueue: netns cleanup_net
[   15.316036][   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)
[   15.316291][   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 7f 7f 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 7f 7f 81 00       	call   0x817fa9
  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
[   15.316991][   T68] RSP: 0018:ffffc90000497690 EFLAGS: 00010046
[   15.317253][   T68] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff9823f90a
[   15.317550][   T68] RDX: fffffbfff388b6cd RSI: 0000000000000008 RDI: ffffffff9c45b660
[   15.317848][   T68] RBP: ffffc900004976f8 R08: 0000000000000001 R09: fffffbfff388b6cc
[   15.318142][   T68] R10: ffffffff9c45b667 R11: ffffc90000497180 R12: 0000000000000000
[   15.318444][   T68] R13: 0000000000000286 R14: ffff88800cd54000 R15: dffffc0000000000
[   15.318749][   T68] FS:  0000000000000000(0000) GS:ffff888099f10000(0000) knlGS:0000000000000000
[   15.319089][   T68] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   15.319337][   T68] CR2: 0000000000000000 CR3: 0000000029735005 CR4: 0000000000772ef0
[   15.319633][   T68] PKRU: 55555554
[   15.319784][   T68] Call Trace:
[   15.319938][   T68]  <TASK>
[   15.320040][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   15.320245][   T68]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   15.320442][   T68]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   15.320638][   T68]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   15.320833][   T68]  __cancel_work_sync (kernel/workqueue.c:4383)
[   15.321028][   T68]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   15.321222][   T68]  ? netdev_notify_peers (net/core/dev.c:1891)
[   15.321423][   T68]  ? netif_close_many (net/core/dev.c:1959)
[   15.321616][   T68]  netif_close_many (net/core/dev.c:1959)
[   15.321827][   T68]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   15.322027][   T68]  ? __dev_close_many (net/core/dev.c:1949)
[   15.322224][   T68]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   15.322468][   T68]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   15.322714][   T68]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   15.322910][   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)
[   15.323111][   T68]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   15.323307][   T68]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   15.323506][   T68]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   15.323752][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   15.323948][   T68]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   15.324150][   T68]  default_device_exit_batch (net/core/dev.c:13229)
[   15.324350][   T68]  ? unregister_netdev (net/core/dev.c:13204)
[   15.324547][   T68]  ops_undo_list (net/core/net_namespace.c:251)
[   15.324744][   T68]  ? netns_get (net/core/net_namespace.c:223)
[   15.324941][   T68]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   15.325146][   T68]  cleanup_net (net/core/net_namespace.c:698)
[   15.325340][   T68]  ? net_passive_dec (net/core/net_namespace.c:660)
[   15.325564][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.325728][   T68]  process_one_work (kernel/workqueue.c:3268)
[   15.325893][   T68]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   15.326056][   T68]  ? assign_work (kernel/workqueue.c:1206)
[   15.326270][   T68]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   15.326465][   T68]  ? rescuer_thread (kernel/workqueue.c:3373)
[   15.326658][   T68]  kthread (kernel/kthread.c:463)
[   15.326804][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.326996][   T68]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   15.327193][   T68]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   15.327388][   T68]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.327586][   T68]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.327780][   T68]  ret_from_fork (arch/x86/kernel/process.c:164)
[   15.327975][   T68]  ? 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