======================================
| xx__-> [    2.002586] ------------[ cut here ]------------
| [    2.002713] refcount_t: underflow; use-after-free.
| [    2.002779] WARNING: CPU: 3 PID: 67 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [    2.002876] Modules linked in: veth
[    2.003031] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    2.003104] Workqueue: netns cleanup_net
[    2.003153] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[    2.003218] Code: 92 e8 f8 c3 ba ff 90 0f 0b 90 90 c3 80 3d 39 c1 eb 00 00 75 89 c6 05 30 c1 eb 00 01 90 48 c7 c7 30 a0 f1 92 e8 d5 c3 ba ff 90 <0f> 0b 90 90 c3 80 3d 14 c1 eb 00 00 0f 85 62 ff ff ff c6 05 07 c1
All code
========
   0:	92                   	xchg   %eax,%edx
   1:	e8 f8 c3 ba ff       	call   0xffffffffffbac3fe
   6:	90                   	nop
   7:	0f 0b                	ud2
   9:	90                   	nop
   a:	90                   	nop
   b:	c3                   	ret
   c:	80 3d 39 c1 eb 00 00 	cmpb   $0x0,0xebc139(%rip)        # 0xebc14c
  13:	75 89                	jne    0xffffffffffffff9e
  15:	c6 05 30 c1 eb 00 01 	movb   $0x1,0xebc130(%rip)        # 0xebc14c
  1c:	90                   	nop
  1d:	48 c7 c7 30 a0 f1 92 	mov    $0xffffffff92f1a030,%rdi
  24:	e8 d5 c3 ba ff       	call   0xffffffffffbac3fe
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	80 3d 14 c1 eb 00 00 	cmpb   $0x0,0xebc114(%rip)        # 0xebc14a
  36:	0f 85 62 ff ff ff    	jne    0xffffffffffffff9e
  3c:	c6                   	.byte 0xc6
  3d:	05                   	.byte 0x5
  3e:	07                   	(bad)
  3f:	c1                   	.byte 0xc1

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	80 3d 14 c1 eb 00 00 	cmpb   $0x0,0xebc114(%rip)        # 0xebc120
   c:	0f 85 62 ff ff ff    	jne    0xffffffffffffff74
  12:	c6                   	.byte 0xc6
  13:	05                   	.byte 0x5
  14:	07                   	(bad)
  15:	c1                   	.byte 0xc1
[    2.003406] RSP: 0018:ffff9f1bc0257d50 EFLAGS: 00010286
[    2.003462] RAX: 0000000000000000 RBX: ffff9f1bc0257d60 RCX: 00000000ffffdfff
[    2.003543] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[    2.003617] RBP: ffff9f1bc0257880 R08: ffffffff93356a28 R09: 00000000ffffdfff
[    2.003700] R10: ffffffff93276a40 R11: ffffffff93326a40 R12: dead000000000122
[    2.003782] R13: 00000000fffb735c R14: 0000000000000001 R15: ffff8c44c30dc000
[    2.003868] FS:  0000000000000000(0000) GS:ffff8c456b362000(0000) knlGS:0000000000000000
[    2.003958] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.004021] CR2: 00007fdbd26daa50 CR3: 000000000319f005 CR4: 0000000000772ef0
[    2.004104] PKRU: 55555554
[    2.004131] Call Trace:
[    2.004161]  <TASK>
[    2.004196]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[    2.004248]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[    2.004295]  cleanup_net (net/core/net_namespace.c:698)
[    2.004337]  process_one_work (kernel/workqueue.c:3268)
[    2.004387]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[    2.004435]  ? rescuer_thread (kernel/workqueue.c:3373)
[    2.004479]  kthread (kernel/kthread.c:463)
[    2.004526]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    2.004590]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    2.004635]  ret_from_fork (arch/x86/kernel/process.c:164)
[    2.004677]  ? kthreads_online_cpu (kernel/kthread.c:412)


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