======================================
| [    4.712788] ------------[ cut here ]------------
| [    4.712892] refcount_t: underflow; use-after-free.
| [    4.712982] WARNING: CPU: 2 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [    4.713084] Modules linked in:
[    4.713251] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    4.713335] Workqueue: netns cleanup_net
[    4.713399] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[    4.713470] Code: a1 e8 88 98 ba ff 90 0f 0b 90 90 c3 80 3d 69 b4 eb 00 00 75 89 c6 05 60 b4 eb 00 01 90 48 c7 c7 98 6e b4 a1 e8 65 98 ba ff 90 <0f> 0b 90 90 c3 80 3d 44 b4 eb 00 00 0f 85 62 ff ff ff c6 05 37 b4
All code
========
   0:	a1 e8 88 98 ba ff 90 	movabs 0xb0f90ffba9888e8,%eax
   7:	0f 0b 
   9:	90                   	nop
   a:	90                   	nop
   b:	c3                   	ret
   c:	80 3d 69 b4 eb 00 00 	cmpb   $0x0,0xebb469(%rip)        # 0xebb47c
  13:	75 89                	jne    0xffffffffffffff9e
  15:	c6 05 60 b4 eb 00 01 	movb   $0x1,0xebb460(%rip)        # 0xebb47c
  1c:	90                   	nop
  1d:	48 c7 c7 98 6e b4 a1 	mov    $0xffffffffa1b46e98,%rdi
  24:	e8 65 98 ba ff       	call   0xffffffffffba988e
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	80 3d 44 b4 eb 00 00 	cmpb   $0x0,0xebb444(%rip)        # 0xebb47a
  36:	0f 85 62 ff ff ff    	jne    0xffffffffffffff9e
  3c:	c6                   	.byte 0xc6
  3d:	05                   	.byte 0x5
  3e:	37                   	(bad)
  3f:	b4                   	.byte 0xb4

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	80 3d 44 b4 eb 00 00 	cmpb   $0x0,0xebb444(%rip)        # 0xebb450
   c:	0f 85 62 ff ff ff    	jne    0xffffffffffffff74
  12:	c6                   	.byte 0xc6
  13:	05                   	.byte 0x5
  14:	37                   	(bad)
  15:	b4                   	.byte 0xb4
[    4.713654] RSP: 0000:ffffbdc500067d50 EFLAGS: 00010286
[    4.713725] RAX: 0000000000000000 RBX: ffffbdc500067d60 RCX: 00000000ffffdfff
[    4.713827] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[    4.713928] RBP: ffffbdc500067878 R08: ffffffffa1f56a28 R09: 00000000ffffdfff
[    4.714030] R10: ffffffffa1e76a40 R11: ffffffffa1f26a40 R12: dead000000000122
[    4.714130] R13: 00000000fffb7e0a R14: 0000000000000001 R15: ffff9f6443e22000
[    4.714232] FS:  0000000000000000(0000) GS:ffff9f64dc6b7000(0000) knlGS:0000000000000000
[    4.714337] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    4.714422] CR2: 00007f00d198a000 CR3: 000000001c041005 CR4: 0000000000772ef0
[    4.714516] PKRU: 55555554
[    4.714562] Call Trace:
[    4.714610]  <TASK>
[    4.714658]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[    4.714725]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[    4.714801]  cleanup_net (net/core/net_namespace.c:698)
[    4.714866]  process_one_work (kernel/workqueue.c:3268)
[    4.714934]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[    4.715000]  ? rescuer_thread (kernel/workqueue.c:3373)
[    4.715062]  kthread (kernel/kthread.c:463)
[    4.715134]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    4.715210]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    4.715294]  ret_from_fork (arch/x86/kernel/process.c:164)
[    4.715363]  ? kthreads_online_cpu (kernel/kthread.c:412)


Finger prints:
refcount_warn_saturate:netdev_run_todo:ops_undo_list:cleanup_net:process_one_work