======================================
| [   30.826198][   T12] ==================================================================
| [   30.826578][   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)
| [   30.826921][   T12] Write of size 8 at addr 0000000000000000 by task kworker/u16:0/12
| [   30.827207][   T12]
[   30.827320][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   30.827324][   T12] Workqueue: netns cleanup_net
[   30.827348][   T12] Call Trace:
[   30.827355][   T12]  <TASK>
[   30.827359][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[   30.827379][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   30.827383][   T12]  kasan_report (mm/kasan/report.c:597)
[   30.827400][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   30.827406][   T12]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   30.827410][   T12]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   30.827415][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   30.827418][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   30.827429][   T12]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   30.827437][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[   30.827442][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   30.827450][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[   30.827453][   T12]  ? netif_close_many (net/core/dev.c:1959)
[   30.827458][   T12]  netif_close_many (net/core/dev.c:1959)
[   30.827461][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   30.827476][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[   30.827482][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   30.827486][   T12]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   30.827490][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   30.827496][   T12]  ? default_device_exit_batch (net/core/dev.c:13215)
[   30.827501][   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)
[   30.827505][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   30.827508][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   30.827515][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   30.827518][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   30.827521][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   30.827529][   T12]  default_device_exit_batch (net/core/dev.c:13229)
[   30.827533][   T12]  ? unregister_netdev (net/core/dev.c:13204)
[   30.827539][   T12]  ops_undo_list (net/core/net_namespace.c:251)
[   30.827545][   T12]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   30.827548][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   30.827554][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   30.827558][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   30.827563][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   30.827573][   T12]  process_one_work (kernel/workqueue.c:3268)
[   30.827580][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   30.827586][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   30.827590][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   30.827596][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   30.827600][   T12]  kthread (kernel/kthread.c:463)
[   30.827607][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   30.827610][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   30.827623][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   30.827627][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   30.827630][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   30.827634][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   30.827636][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   30.827639][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   30.838717][   T12] #PF: error_code(0x0002) - not-present page
| [   30.838963][   T12] PGD 0 P4D 0
| [   30.839108][   T12] Oops: Oops: 0002 [#1] SMP KASAN
| [   30.839732][   T12] Tainted: [B]=BAD_PAGE
[   30.839899][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   30.840131][   T12] Workqueue: netns cleanup_net
[   30.840332][   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)
[   30.840580][   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 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
[   30.841247][   T12] RSP: 0000:ffffc900000c7680 EFLAGS: 00010046
[   30.841489][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffb7e49b8a
[   30.841782][   T12] RDX: fffffbfff796cacd RSI: 0000000000000008 RDI: ffffffffbcb65660
[   30.842072][   T12] RBP: ffffc900000c76e8 R08: 0000000000000001 R09: fffffbfff796cacc
[   30.842355][   T12] R10: ffffffffbcb65667 R11: ffffc900000c7140 R12: 0000000000000000
[   30.842645][   T12] R13: 0000000000000282 R14: ffff8880049ac000 R15: dffffc0000000000
[   30.842942][   T12] FS:  0000000000000000(0000) GS:ffff8880b0587000(0000) knlGS:0000000000000000
[   30.843256][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   30.843496][   T12] CR2: 0000000000000000 CR3: 000000000aaa9002 CR4: 0000000000772ef0
[   30.843778][   T12] PKRU: 55555554
[   30.843936][   T12] Call Trace:
[   30.844079][   T12]  <TASK>
[   30.844187][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   30.844374][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   30.844575][   T12]  ? queue_delayed_work_on (kernel/workqueue.c:2565 (discriminator 1))
[   30.844762][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[   30.844974][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   30.845166][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[   30.845344][   T12]  ? netif_close_many (net/core/dev.c:1959)
[   30.845535][   T12]  netif_close_many (net/core/dev.c:1959)
[   30.845718][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   30.845911][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[   30.846090][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   30.846312][   T12]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   30.846513][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   30.846747][   T12]  ? default_device_exit_batch (net/core/dev.c:13215)
[   30.846945][   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)
[   30.847126][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   30.847305][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   30.847500][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   30.847723][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   30.847920][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   30.848204][   T12]  default_device_exit_batch (net/core/dev.c:13229)
[   30.848378][   T12]  ? unregister_netdev (net/core/dev.c:13204)
[   30.848572][   T12]  ops_undo_list (net/core/net_namespace.c:251)
[   30.848766][   T12]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   30.849057][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   30.849235][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   30.849415][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   30.849609][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   30.849797][   T12]  process_one_work (kernel/workqueue.c:3268)
[   30.849992][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   30.850174][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   30.850348][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   30.850637][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   30.850819][   T12]  kthread (kernel/kthread.c:463)
[   30.850979][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   30.851153][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   30.851436][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   30.851642][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   30.851828][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   30.852022][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   30.852293][   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