======================================
| [   15.146989] ------------[ cut here ]------------
| [   15.147070] refcount_t: underflow; use-after-free.
| [   15.147134] WARNING: CPU: 1 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   15.147224] Modules linked in: macvlan 8021q vxlan ip6_udp_tunnel udp_tunnel bridge stp llc vrf veth
[   15.147416] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   15.147483] Workqueue: netns cleanup_net
[   15.147529] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   15.147581] Code: 85 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 d1 85 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:	85 e8                	test   %ebp,%eax
   2:	18 df                	sbb    %bl,%bh
   4:	ba ff 90 0f 0b       	mov    $0xb0f90ff,%edx
   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 d1 85 	mov    $0xffffffff85d1e028,%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
[   15.147766] RSP: 0018:ffffb50640067d50 EFLAGS: 00010286
[   15.147818] RAX: 0000000000000000 RBX: ffffb50640067d60 RCX: 00000000ffffdfff
[   15.147899] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[   15.147982] RBP: ffffb50640067868 R08: ffffffff86156a28 R09: 00000000ffffdfff
[   15.148063] R10: ffffffff86076a40 R11: ffffffff86126a40 R12: dead000000000122
[   15.148142] R13: 00000000fffba6c7 R14: 0000000000000001 R15: ffff91f7c862c000
[   15.148223] FS:  0000000000000000(0000) GS:ffff91f878459000(0000) knlGS:0000000000000000
[   15.148311] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   15.148377] CR2: 00007f3d68f401c0 CR3: 00000000098e2006 CR4: 0000000000772ef0
[   15.148460] PKRU: 55555554
[   15.148485] Call Trace:
[   15.148514]  <TASK>
[   15.148539]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   15.148588]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   15.148633]  cleanup_net (net/core/net_namespace.c:698)
[   15.148672]  process_one_work (kernel/workqueue.c:3268)
[   15.148720]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   15.148767]  ? rescuer_thread (kernel/workqueue.c:3373)
[   15.148813]  kthread (kernel/kthread.c:463)
[   15.148854]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   15.148907]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   15.148960]  ret_from_fork (arch/x86/kernel/process.c:164)
[   15.149037]  ? kthreads_online_cpu (kernel/kthread.c:412)


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