======================================
| [    2.462708] #PF: supervisor write access in kernel mode
| [    2.462750] #PF: error_code(0x0002) - not-present page
| [    2.462793] PGD 0 P4D 0
| [    2.462822] Oops: Oops: 0002 [#1] SMP
[    2.462944] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    2.463002] Workqueue: netns cleanup_net
[    2.463047] RIP: 0010:work_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072 kernel/workqueue.c:2160)
[    2.463101] Code: 83 e6 01 41 57 41 56 4c 8d 77 20 41 55 41 54 41 89 f4 55 48 89 d5 53 48 89 fb 9c 58 fa 48 89 45 00 45 85 e4 0f 85 8a 00 00 00 <f0> 48 0f ba 2b 00 41 0f 92 c5 72 0e 5b 44 89 e8 5d 41 5c 41 5d 41
All code
========
   0:	83 e6 01             	and    $0x1,%esi
   3:	41 57                	push   %r15
   5:	41 56                	push   %r14
   7:	4c 8d 77 20          	lea    0x20(%rdi),%r14
   b:	41 55                	push   %r13
   d:	41 54                	push   %r12
   f:	41 89 f4             	mov    %esi,%r12d
  12:	55                   	push   %rbp
  13:	48 89 d5             	mov    %rdx,%rbp
  16:	53                   	push   %rbx
  17:	48 89 fb             	mov    %rdi,%rbx
  1a:	9c                   	pushf
  1b:	58                   	pop    %rax
  1c:	fa                   	cli
  1d:	48 89 45 00          	mov    %rax,0x0(%rbp)
  21:	45 85 e4             	test   %r12d,%r12d
  24:	0f 85 8a 00 00 00    	jne    0xb4
  2a:*	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)		<-- trapping instruction
  30:	41 0f 92 c5          	setb   %r13b
  34:	72 0e                	jb     0x44
  36:	5b                   	pop    %rbx
  37:	44 89 e8             	mov    %r13d,%eax
  3a:	5d                   	pop    %rbp
  3b:	41 5c                	pop    %r12
  3d:	41 5d                	pop    %r13
  3f:	41                   	rex.B

Code starting with the faulting instruction
===========================================
   0:	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)
   6:	41 0f 92 c5          	setb   %r13b
   a:	72 0e                	jb     0x1a
   c:	5b                   	pop    %rbx
   d:	44 89 e8             	mov    %r13d,%eax
  10:	5d                   	pop    %rbp
  11:	41 5c                	pop    %r12
  13:	41 5d                	pop    %r13
  15:	41                   	rex.B
[    2.463258] RSP: 0018:ffff9f664024fc30 EFLAGS: 00010046
[    2.463303] RAX: 0000000000000246 RBX: 0000000000000000 RCX: 0000000000000004
[    2.463371] RDX: ffff9f664024fc68 RSI: 0000000000000000 RDI: 0000000000000000
[    2.463439] RBP: ffff9f664024fc68 R08: 0000000000000400 R09: 0000000000000001
[    2.463506] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
[    2.463574] R13: ffff9f664024fd60 R14: 0000000000000020 R15: ffff9f664024fdf0
[    2.463645] FS:  0000000000000000(0000) GS:ffff89af30591000(0000) knlGS:0000000000000000
[    2.463724] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.463786] CR2: 0000000000000000 CR3: 0000000006c46001 CR4: 0000000000772ef0
[    2.463856] PKRU: 55555554
[    2.463877] Call Trace:
[    2.463902]  <TASK>
[    2.463932]  __cancel_work (kernel/workqueue.c:4366)
[    2.463971]  ? dev_deactivate_many (net/sched/sch_generic.c:1324 net/sched/sch_generic.c:1382)
[    2.464023]  __cancel_work_sync (kernel/workqueue.c:4381)
[    2.464063]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[    2.464104]  netif_close_many (net/core/dev.c:1959)
[    2.464138]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[    2.464191]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[    2.464232]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[    2.464272]  cleanup_net (net/core/net_namespace.c:698)
[    2.464305]  process_one_work (kernel/workqueue.c:3268)
[    2.464347]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[    2.464387]  ? rescuer_thread (kernel/workqueue.c:3373)
[    2.464426]  kthread (kernel/kthread.c:463)
[    2.464466]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    2.464512]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    2.464563]  ret_from_fork (arch/x86/kernel/process.c:164)
[    2.464605]  ? kthreads_online_cpu (kernel/kthread.c:412)


Finger prints:
work_grab_pending:__cancel_work:__cancel_work_sync:__dev_close_many:netif_close_many