======================================
| [  206.060471][   T12] ==================================================================
| [  206.060926][   T12] 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)
| [  206.061422][   T12] Write of size 8 at addr 0000000000000000 by task kworker/u16:0/12
| [  206.061837][   T12]
[  206.061996][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  206.062000][   T12] Workqueue: netns cleanup_net
[  206.062015][   T12] Call Trace:
[  206.062018][   T12]  <TASK>
[  206.062022][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[  206.062031][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  206.062037][   T12]  kasan_report (mm/kasan/report.c:597)
[  206.062048][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  206.062057][   T12]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[  206.062062][   T12]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  206.062071][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  206.062076][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  206.062084][   T12]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[  206.062092][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[  206.062098][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  206.062105][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[  206.062111][   T12]  ? netif_close_many (net/core/dev.c:1959)
[  206.062118][   T12]  netif_close_many (net/core/dev.c:1959)
[  206.062123][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  206.062130][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[  206.062135][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  206.062143][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  206.062149][   T12]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[  206.062156][   T12]  ? 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)
[  206.062161][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  206.062167][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  206.062174][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  206.062179][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  206.062185][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  206.062195][   T12]  default_device_exit_batch (net/core/dev.c:13229)
[  206.062201][   T12]  ? unregister_netdev (net/core/dev.c:13204)
[  206.062212][   T12]  ops_undo_list (net/core/net_namespace.c:251)
[  206.062223][   T12]  ? netns_get (net/core/net_namespace.c:223)
[  206.062228][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  206.062237][   T12]  cleanup_net (net/core/net_namespace.c:698)
[  206.062243][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[  206.062250][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  206.062261][   T12]  process_one_work (kernel/workqueue.c:3268)
[  206.062273][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  206.062283][   T12]  ? assign_work (kernel/workqueue.c:1206)
[  206.062290][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  206.062300][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[  206.062307][   T12]  kthread (kernel/kthread.c:463)
[  206.062315][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  206.062319][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  206.062329][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  206.062337][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  206.062342][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  206.062348][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[  206.062353][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  206.062358][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  206.078518][   T12] #PF: error_code(0x0002) - not-present page
| [  206.078849][   T12] PGD 0 P4D 0
| [  206.079057][   T12] Oops: Oops: 0002 [#1] SMP KASAN
| [  206.080155][   T12] Tainted: [B]=BAD_PAGE
[  206.080547][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  206.081066][   T12] Workqueue: netns cleanup_net
[  206.081542][   T12] 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)
[  206.082075][   T12] 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 df 81 84 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 df 81 84 00       	call   0x848209
  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
[  206.083024][   T12] RSP: 0018:ffffc900000c7690 EFLAGS: 00010046
[  206.083360][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff9ce40aaa
[  206.083766][   T12] RDX: fffffbfff420fecd RSI: 0000000000000008 RDI: ffffffffa107f660
[  206.084179][   T12] RBP: ffffc900000c76f8 R08: 0000000000000001 R09: fffffbfff420fecc
[  206.084578][   T12] R10: ffffffffa107f667 R11: ffffc900000c7180 R12: 0000000000000000
[  206.084997][   T12] R13: 0000000000000286 R14: ffff888010021000 R15: dffffc0000000000
[  206.085408][   T12] FS:  0000000000000000(0000) GS:ffff88808f5ec000(0000) knlGS:0000000000000000
[  206.086277][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  206.086629][   T12] CR2: 0000000000000000 CR3: 0000000037735006 CR4: 0000000000772ef0
[  206.087034][   T12] PKRU: 55555554
[  206.087243][   T12] Call Trace:
[  206.087637][   T12]  <TASK>
[  206.087782][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  206.088066][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  206.088361][   T12]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[  206.088651][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[  206.088924][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  206.089199][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[  206.089658][   T12]  ? netif_close_many (net/core/dev.c:1959)
[  206.089931][   T12]  netif_close_many (net/core/dev.c:1959)
[  206.090202][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  206.090484][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[  206.090768][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  206.091109][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  206.091457][   T12]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[  206.091711][   T12]  ? 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)
[  206.091986][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  206.092432][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  206.092709][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  206.093085][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  206.093357][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  206.093638][   T12]  default_device_exit_batch (net/core/dev.c:13229)
[  206.093923][   T12]  ? unregister_netdev (net/core/dev.c:13204)
[  206.094201][   T12]  ops_undo_list (net/core/net_namespace.c:251)
[  206.094502][   T12]  ? netns_get (net/core/net_namespace.c:223)
[  206.094769][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  206.095052][   T12]  cleanup_net (net/core/net_namespace.c:698)
[  206.095341][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[  206.095642][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  206.095935][   T12]  process_one_work (kernel/workqueue.c:3268)
[  206.096241][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  206.096517][   T12]  ? assign_work (kernel/workqueue.c:1206)
[  206.096793][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  206.097256][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[  206.097900][   T12]  kthread (kernel/kthread.c:463)
[  206.098110][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  206.098413][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  206.098691][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  206.098967][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  206.099245][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  206.099512][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[  206.099782][   T12]  ? 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