======================================
| [  144.346803][   T12] ==================================================================
| [  144.347123][   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)
| [  144.347414][   T12] Write of size 8 at addr 0000000000000000 by task kworker/u16:0/12
| [  144.347684][   T12]
[  144.347799][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  144.347804][   T12] Workqueue: netns cleanup_net
[  144.347813][   T12] Call Trace:
[  144.347817][   T12]  <TASK>
[  144.347820][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[  144.347826][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  144.347830][   T12]  kasan_report (mm/kasan/report.c:597)
[  144.347838][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  144.347843][   T12]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[  144.347846][   T12]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[  144.347851][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  144.347854][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  144.347858][   T12]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  144.347864][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[  144.347868][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  144.347874][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[  144.347877][   T12]  ? netif_close_many (net/core/dev.c:1959)
[  144.347881][   T12]  netif_close_many (net/core/dev.c:1959)
[  144.347884][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  144.347889][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[  144.347893][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  144.347897][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  144.347902][   T12]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[  144.347906][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  144.347910][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  144.347914][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  144.347916][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  144.347919][   T12]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[  144.347923][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  144.347929][   T12]  default_device_exit_batch (net/core/dev.c:13229)
[  144.347933][   T12]  ? unregister_netdev (net/core/dev.c:13204)
[  144.347939][   T12]  ops_undo_list (net/core/net_namespace.c:251)
[  144.347948][   T12]  ? netns_get (net/core/net_namespace.c:223)
[  144.347951][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  144.347956][   T12]  cleanup_net (net/core/net_namespace.c:698)
[  144.347959][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[  144.347962][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  144.347967][   T12]  process_one_work (kernel/workqueue.c:3268)
[  144.347973][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  144.347978][   T12]  ? assign_work (kernel/workqueue.c:1206)
[  144.347982][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  144.347988][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[  144.347991][   T12]  kthread (kernel/kthread.c:463)
[  144.347995][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  144.347997][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  144.348004][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  144.348008][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  144.348011][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  144.348014][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[  144.348018][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  144.348020][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [  144.358393][   T12] #PF: error_code(0x0002) - not-present page
| [  144.358615][   T12] PGD 0 P4D 0
| [  144.358753][   T12] Oops: Oops: 0002 [#1] SMP KASAN
| [  144.359335][   T12] Tainted: [B]=BAD_PAGE
[  144.359464][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  144.359689][   T12] Workqueue: netns cleanup_net
[  144.359877][   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)
[  144.360108][   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
[  144.360786][   T12] RSP: 0018:ffffc900000c7690 EFLAGS: 00010046
[  144.361001][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffaf640aaa
[  144.361243][   T12] RDX: fffffbfff670fecd RSI: 0000000000000008 RDI: ffffffffb387f660
[  144.361502][   T12] RBP: ffffc900000c76f8 R08: 0000000000000001 R09: fffffbfff670fecc
[  144.361791][   T12] R10: ffffffffb387f667 R11: ffffc900000c7180 R12: 0000000000000000
[  144.362045][   T12] R13: 0000000000000286 R14: ffff888007f6c000 R15: dffffc0000000000
[  144.362311][   T12] FS:  0000000000000000(0000) GS:ffff8880829ec000(0000) knlGS:0000000000000000
[  144.362616][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  144.362841][   T12] CR2: 0000000000000000 CR3: 0000000019735002 CR4: 0000000000772ef0
[  144.363110][   T12] PKRU: 55555554
[  144.363241][   T12] Call Trace:
[  144.363384][   T12]  <TASK>
[  144.363473][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[  144.363657][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[  144.363838][   T12]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[  144.364015][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[  144.364192][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[  144.364364][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[  144.364534][   T12]  ? netif_close_many (net/core/dev.c:1959)
[  144.364705][   T12]  netif_close_many (net/core/dev.c:1959)
[  144.364879][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[  144.365054][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[  144.365221][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[  144.365438][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[  144.365660][   T12]  ? find_held_lock (kernel/locking/lockdep.c:5350)
[  144.365836][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  144.366014][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[  144.366178][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[  144.366345][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[  144.366576][   T12]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[  144.366753][   T12]  ? unregister_netdevice_many (net/core/dev.c:12441)
[  144.366928][   T12]  default_device_exit_batch (net/core/dev.c:13229)
[  144.367089][   T12]  ? unregister_netdev (net/core/dev.c:13204)
[  144.367255][   T12]  ops_undo_list (net/core/net_namespace.c:251)
[  144.367428][   T12]  ? netns_get (net/core/net_namespace.c:223)
[  144.367610][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[  144.367791][   T12]  cleanup_net (net/core/net_namespace.c:698)
[  144.367962][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[  144.368124][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  144.368293][   T12]  process_one_work (kernel/workqueue.c:3268)
[  144.368466][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[  144.368649][   T12]  ? assign_work (kernel/workqueue.c:1206)
[  144.368847][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[  144.369027][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[  144.369195][   T12]  kthread (kernel/kthread.c:463)
[  144.369338][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  144.369621][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[  144.369826][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[  144.369995][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[  144.370254][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[  144.370438][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[  144.370617][   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