======================================
| xx__-> [    1.799269] ------------[ cut here ]------------
| [    1.799343] refcount_t: underflow; use-after-free.
| [    1.799408] WARNING: CPU: 0 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [    1.799505] Modules linked in: veth
[    1.799661] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    1.799731] Workqueue: netns cleanup_net
[    1.799782] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[    1.799838] Code: 98 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 98 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:	98                   	cwtl
   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 91 98 	mov    $0xffffffff9891a030,%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
[    1.800042] RSP: 0018:ffffbc3040067d50 EFLAGS: 00010286
[    1.800099] RAX: 0000000000000000 RBX: ffffbc3040067d60 RCX: 00000000ffffdfff
[    1.800183] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[    1.800269] RBP: ffffbc3040067880 R08: ffffffff98d56a28 R09: 00000000ffffdfff
[    1.800358] R10: ffffffff98c76a40 R11: ffffffff98d26a40 R12: dead000000000122
[    1.800442] R13: 00000000fffb72a9 R14: 0000000000000001 R15: ffff9cc144ae4000
[    1.800530] FS:  0000000000000000(0000) GS:ffff9cc1e57e2000(0000) knlGS:0000000000000000
[    1.800622] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.800693] CR2: 00007f324116c000 CR3: 0000000004913001 CR4: 0000000000772ef0
[    1.800779] PKRU: 55555554
[    1.800809] Call Trace:
[    1.800826]  <TASK>
[    1.800851]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[    1.800897]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[    1.800944]  cleanup_net (net/core/net_namespace.c:698)
[    1.800986]  process_one_work (kernel/workqueue.c:3268)
[    1.801042]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[    1.801101]  ? rescuer_thread (kernel/workqueue.c:3373)
[    1.801151]  kthread (kernel/kthread.c:463)
[    1.801202]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    1.801261]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    1.801321]  ret_from_fork (arch/x86/kernel/process.c:164)
[    1.801374]  ? kthreads_online_cpu (kernel/kthread.c:412)


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