======================================
| xx__-> [    1.859568] ------------[ cut here ]------------
| [    1.859691] refcount_t: underflow; use-after-free.
| [    1.859792] WARNING: CPU: 1 PID: 66 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [    1.859871] Modules linked in: veth
[    1.859976] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    1.860025] Workqueue: netns cleanup_net
[    1.860067] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[    1.860112] Code: 86 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 91 86 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:	86 e8                	xchg   %ch,%al
   2:	f8                   	clc
   3:	c3                   	ret
   4:	ba ff 90 0f 0b       	mov    $0xb0f90ff,%edx
   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 91 86 	mov    $0xffffffff8691a030,%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
[    1.860266] RSP: 0018:ffffac1e8024bd50 EFLAGS: 00010286
[    1.860309] RAX: 0000000000000000 RBX: ffffac1e8024bd60 RCX: 00000000ffffdfff
[    1.860373] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[    1.860429] RBP: ffffac1e8024b880 R08: ffffffff86d56a28 R09: 00000000ffffdfff
[    1.860484] R10: ffffffff86c76a40 R11: ffffffff86d26a40 R12: dead000000000122
[    1.860559] R13: 00000000fffb72d6 R14: 0000000000000001 R15: ffff957642fdc000
[    1.860625] FS:  0000000000000000(0000) GS:ffff9576f7862000(0000) knlGS:0000000000000000
[    1.860691] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.860747] CR2: 00007f2fddf86f20 CR3: 0000000013441001 CR4: 0000000000772ef0
[    1.860815] PKRU: 55555554
[    1.860840] Call Trace:
[    1.860860]  <TASK>
[    1.860884]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[    1.860931]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[    1.860972]  cleanup_net (net/core/net_namespace.c:698)
[    1.861007]  process_one_work (kernel/workqueue.c:3268)
[    1.861053]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[    1.861091]  ? rescuer_thread (kernel/workqueue.c:3373)
[    1.861136]  kthread (kernel/kthread.c:463)
[    1.861178]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    1.861232]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    1.861285]  ret_from_fork (arch/x86/kernel/process.c:164)
[    1.861324]  ? kthreads_online_cpu (kernel/kthread.c:412)


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