======================================
| [   12.070899] ------------[ cut here ]------------
| [   12.071032] refcount_t: underflow; use-after-free.
| [   12.071099] WARNING: CPU: 3 PID: 64 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   12.071174] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel bridge stp llc sch_ingress vrf veth
[   12.071356] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   12.071408] Workqueue: netns cleanup_net
[   12.071448] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   12.071501] Code: 9f e8 18 df ba ff 90 0f 0b 90 90 c3 80 3d f9 da eb 00 00 75 89 c6 05 f0 da eb 00 01 90 48 c7 c7 28 e0 b1 9f e8 f5 de ba ff 90 <0f> 0b 90 90 c3 80 3d d4 da eb 00 00 0f 85 62 ff ff ff c6 05 c7 da
All code
========
   0:	9f                   	lahf
   1:	e8 18 df ba ff       	call   0xffffffffffbadf1e
   6:	90                   	nop
   7:	0f 0b                	ud2
   9:	90                   	nop
   a:	90                   	nop
   b:	c3                   	ret
   c:	80 3d f9 da eb 00 00 	cmpb   $0x0,0xebdaf9(%rip)        # 0xebdb0c
  13:	75 89                	jne    0xffffffffffffff9e
  15:	c6 05 f0 da eb 00 01 	movb   $0x1,0xebdaf0(%rip)        # 0xebdb0c
  1c:	90                   	nop
  1d:	48 c7 c7 28 e0 b1 9f 	mov    $0xffffffff9fb1e028,%rdi
  24:	e8 f5 de ba ff       	call   0xffffffffffbadf1e
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	80 3d d4 da eb 00 00 	cmpb   $0x0,0xebdad4(%rip)        # 0xebdb0a
  36:	0f 85 62 ff ff ff    	jne    0xffffffffffffff9e
  3c:	c6                   	.byte 0xc6
  3d:	05                   	.byte 0x5
  3e:	c7                   	(bad)
  3f:	da                   	.byte 0xda

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	80 3d d4 da eb 00 00 	cmpb   $0x0,0xebdad4(%rip)        # 0xebdae0
   c:	0f 85 62 ff ff ff    	jne    0xffffffffffffff74
  12:	c6                   	.byte 0xc6
  13:	05                   	.byte 0x5
  14:	c7                   	(bad)
  15:	da                   	.byte 0xda
[   12.071652] RSP: 0018:ffffb81ec0237d50 EFLAGS: 00010286
[   12.071711] RAX: 0000000000000000 RBX: ffffb81ec0237d60 RCX: 00000000ffffdfff
[   12.071804] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[   12.071891] RBP: ffffb81ec0237868 R08: ffffffff9ff56a28 R09: 00000000ffffdfff
[   12.071978] R10: ffffffff9fe76a40 R11: ffffffff9ff26a40 R12: dead000000000122
[   12.072054] R13: 00000000fffb9ac1 R14: 0000000000000001 R15: ffff891c893ed000
[   12.072141] FS:  0000000000000000(0000) GS:ffff891d1e759000(0000) knlGS:0000000000000000
[   12.072231] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   12.072303] CR2: 00007fef5e466e80 CR3: 0000000030841001 CR4: 0000000000772ef0
[   12.072385] PKRU: 55555554
[   12.072412] Call Trace:
[   12.072437]  <TASK>
[   12.072468]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   12.072513]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   12.072551]  cleanup_net (net/core/net_namespace.c:698)
[   12.072721]  process_one_work (kernel/workqueue.c:3268)
[   12.072769]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   12.072812]  ? rescuer_thread (kernel/workqueue.c:3373)
[   12.072857]  kthread (kernel/kthread.c:463)
[   12.072909]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   12.072951]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   12.072997]  ret_from_fork (arch/x86/kernel/process.c:164)
[   12.073044]  ? kthreads_online_cpu (kernel/kthread.c:412)


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