======================================
| [   68.460555][   T70] ==================================================================
| [   68.460964][   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)
| [   68.461305][   T70] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/70
| [   68.461617][   T70]
[   68.461738][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   68.461742][   T70] Workqueue: netns cleanup_net
[   68.461754][   T70] Call Trace:
[   68.461763][   T70]  <TASK>
[   68.461767][   T70]  dump_stack_lvl (lib/dump_stack.c:123)
[   68.461777][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   68.461781][   T70]  kasan_report (mm/kasan/report.c:597)
[   68.461792][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   68.461801][   T70]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   68.461810][   T70]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   68.461816][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   68.461819][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   68.461824][   T70]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   68.461832][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   68.461837][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   68.461843][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   68.461846][   T70]  ? __mutex_lock (./arch/x86/include/asm/preempt.h:104 kernel/locking/mutex.c:739 kernel/locking/mutex.c:760)
[   68.461857][   T70]  netif_close_many (net/core/dev.c:1959)
[   68.461860][   T70]  ? ww_mutex_lock (kernel/locking/mutex.c:759)
[   68.461863][   T70]  ? worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   68.461866][   T70]  ? kthread (kernel/kthread.c:463)
[   68.461872][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   68.461875][   T70]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   68.461885][   T70]  netif_close_many_and_unlock (net/core/dev.c:12476)
[   68.461890][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12539)
[   68.461895][   T70]  ? __virt_addr_valid (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:979 ./include/linux/mmzone.h:2197 arch/x86/mm/physaddr.c:65)
[   68.461910][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   68.461913][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   68.461917][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   68.461922][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   68.461925][   T70]  ? __call_rcu_common.constprop.0 (kernel/rcu/tree.c:3148)
[   68.461930][   T70]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   68.461936][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   68.461940][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   68.461946][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   68.461952][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   68.461955][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   68.461961][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   68.461966][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   68.461970][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.461977][   T70]  process_one_work (kernel/workqueue.c:3268)
[   68.461983][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   68.461989][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   68.461993][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   68.461999][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   68.462004][   T70]  kthread (kernel/kthread.c:463)
[   68.462007][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.462010][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   68.462014][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   68.462018][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.462021][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.462025][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   68.462028][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.462031][   T70]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   68.473856][   T70] #PF: error_code(0x0002) - not-present page
| [   68.474076][   T70] PGD 0 P4D 0
| [   68.474220][   T70] Oops: Oops: 0002 [#1] SMP KASAN
| [   68.474958][   T70] Tainted: [B]=BAD_PAGE
[   68.475102][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   68.475340][   T70] Workqueue: netns cleanup_net
[   68.475562][   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)
[   68.475929][   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
[   68.476577][   T70] RSP: 0000:ffffc900004b7630 EFLAGS: 00010046
[   68.476938][   T70] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8fe49b8a
[   68.477206][   T70] RDX: fffffbfff296cacd RSI: 0000000000000008 RDI: ffffffff94b65660
[   68.477591][   T70] RBP: ffffc900004b7698 R08: 0000000000000001 R09: fffffbfff296cacc
[   68.477883][   T70] R10: ffffffff94b65667 R11: ffffc900004b7100 R12: 0000000000000000
[   68.478152][   T70] R13: 0000000000000286 R14: ffff888008be4000 R15: dffffc0000000000
[   68.478528][   T70] FS:  0000000000000000(0000) GS:ffff8880d8687000(0000) knlGS:0000000000000000
[   68.478854][   T70] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   68.479072][   T70] CR2: 0000000000000000 CR3: 0000000039b49003 CR4: 0000000000772ef0
[   68.479444][   T70] PKRU: 55555554
[   68.479594][   T70] Call Trace:
[   68.479745][   T70]  <TASK>
[   68.479859][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   68.480147][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   68.480333][   T70]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   68.480523][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   68.480710][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   68.480898][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   68.481075][   T70]  ? __mutex_lock (./arch/x86/include/asm/preempt.h:104 kernel/locking/mutex.c:739 kernel/locking/mutex.c:760)
[   68.481253][   T70]  netif_close_many (net/core/dev.c:1959)
[   68.481427][   T70]  ? ww_mutex_lock (kernel/locking/mutex.c:759)
[   68.481624][   T70]  ? worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   68.481809][   T70]  ? kthread (kernel/kthread.c:463)
[   68.481944][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   68.482117][   T70]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[   68.482297][   T70]  netif_close_many_and_unlock (net/core/dev.c:12476)
[   68.482483][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12539)
[   68.482711][   T70]  ? __virt_addr_valid (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:979 ./include/linux/mmzone.h:2197 arch/x86/mm/physaddr.c:65)
[   68.482899][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   68.483172][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   68.483346][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   68.483781][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   68.484068][   T70]  ? __call_rcu_common.constprop.0 (kernel/rcu/tree.c:3148)
[   68.484286][   T70]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   68.484575][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   68.484869][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   68.485044][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   68.485221][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   68.485403][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   68.485597][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   68.485790][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   68.485974][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.486151][   T70]  process_one_work (kernel/workqueue.c:3268)
[   68.486326][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   68.486512][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   68.486913][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   68.487090][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   68.487268][   T70]  kthread (kernel/kthread.c:463)
[   68.487404][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.487700][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   68.487890][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   68.488064][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   68.488239][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   68.488625][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   68.488811][   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