======================================
| [   51.167658] ------------[ cut here ]------------
| [   51.167729] refcount_t: underflow; use-after-free.
| [   51.167780] WARNING: CPU: 0 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   51.167866] Modules linked in: nft_flow_offload nf_flow_table_inet nf_flow_table nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables veth
[   51.168050] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   51.168102] Workqueue: netns cleanup_net
[   51.168140] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   51.168179] Code: ba e8 18 ed b9 ff 90 0f 0b 90 90 c3 80 3d d9 ea ea 00 00 75 89 c6 05 d0 ea ea 00 01 90 48 c7 c7 78 de 51 ba e8 f5 ec b9 ff 90 <0f> 0b 90 90 c3 80 3d b4 ea ea 00 00 0f 85 62 ff ff ff c6 05 a7 ea
All code
========
   0:	ba e8 18 ed b9       	mov    $0xb9ed18e8,%edx
   5:	ff 90 0f 0b 90 90    	call   *-0x6f6ff4f1(%rax)
   b:	c3                   	ret
   c:	80 3d d9 ea ea 00 00 	cmpb   $0x0,0xeaead9(%rip)        # 0xeaeaec
  13:	75 89                	jne    0xffffffffffffff9e
  15:	c6 05 d0 ea ea 00 01 	movb   $0x1,0xeaead0(%rip)        # 0xeaeaec
  1c:	90                   	nop
  1d:	48 c7 c7 78 de 51 ba 	mov    $0xffffffffba51de78,%rdi
  24:	e8 f5 ec b9 ff       	call   0xffffffffffb9ed1e
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	80 3d b4 ea ea 00 00 	cmpb   $0x0,0xeaeab4(%rip)        # 0xeaeaea
  36:	0f 85 62 ff ff ff    	jne    0xffffffffffffff9e
  3c:	c6                   	.byte 0xc6
  3d:	05                   	.byte 0x5
  3e:	a7                   	cmpsl  %es:(%rdi),%ds:(%rsi)
  3f:	ea                   	(bad)

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	80 3d b4 ea ea 00 00 	cmpb   $0x0,0xeaeab4(%rip)        # 0xeaeac0
   c:	0f 85 62 ff ff ff    	jne    0xffffffffffffff74
  12:	c6                   	.byte 0xc6
  13:	05                   	.byte 0x5
  14:	a7                   	cmpsl  %es:(%rdi),%ds:(%rsi)
  15:	ea                   	(bad)
[   51.168301] RSP: 0018:ffffc1f8c0067d50 EFLAGS: 00010286
[   51.168341] RAX: 0000000000000000 RBX: ffffc1f8c0067d60 RCX: 00000000ffffdfff
[   51.168408] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[   51.168462] RBP: ffffc1f8c0067868 R08: ffffffffba956d28 R09: 00000000ffffdfff
[   51.168511] R10: ffffffffba876d40 R11: ffffffffba926d40 R12: dead000000000122
[   51.168570] R13: 00000000fffc3372 R14: 0000000000000001 R15: ffff9e8fc4f59000
[   51.168637] FS:  0000000000000000(0000) GS:ffff9e9043bd8000(0000) knlGS:0000000000000000
[   51.168694] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   51.168740] CR2: 00007f42351d7a20 CR3: 0000000004ceb001 CR4: 0000000000772ef0
[   51.168799] PKRU: 55555554
[   51.168820] Call Trace:
[   51.168843]  <TASK>
[   51.168867]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   51.168922]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   51.168959]  cleanup_net (net/core/net_namespace.c:698)
[   51.168990]  process_one_work (kernel/workqueue.c:3268)
[   51.169035]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   51.169066]  ? rescuer_thread (kernel/workqueue.c:3373)
[   51.169095]  kthread (kernel/kthread.c:463)
[   51.169129]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   51.169165]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   51.169198]  ret_from_fork (arch/x86/kernel/process.c:164)
[   51.169280]  ? kthreads_online_cpu (kernel/kthread.c:412)


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