======================================
| xx__-> [   13.206800] ------------[ cut here ]------------
| [   13.206878] refcount_t: underflow; use-after-free.
| [   13.206937] WARNING: CPU: 0 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   13.207015] Modules linked in: tcp_diag mptcp_diag inet_diag
[   13.207161] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   13.207215] Workqueue: netns cleanup_net
[   13.207258] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   13.207310] Code: 9f e8 48 df ba ff 90 0f 0b 90 90 c3 80 3d c9 50 ec 00 00 75 89 c6 05 c0 50 ec 00 01 90 48 c7 c7 c8 4a 92 9f e8 25 df ba ff 90 <0f> 0b 90 90 c3 80 3d a4 50 ec 00 00 0f 85 62 ff ff ff c6 05 97 50
All code
========
   0:	9f                   	lahf
   1:	e8 48 df ba ff       	call   0xffffffffffbadf4e
   6:	90                   	nop
   7:	0f 0b                	ud2
   9:	90                   	nop
   a:	90                   	nop
   b:	c3                   	ret
   c:	80 3d c9 50 ec 00 00 	cmpb   $0x0,0xec50c9(%rip)        # 0xec50dc
  13:	75 89                	jne    0xffffffffffffff9e
  15:	c6 05 c0 50 ec 00 01 	movb   $0x1,0xec50c0(%rip)        # 0xec50dc
  1c:	90                   	nop
  1d:	48 c7 c7 c8 4a 92 9f 	mov    $0xffffffff9f924ac8,%rdi
  24:	e8 25 df ba ff       	call   0xffffffffffbadf4e
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	80 3d a4 50 ec 00 00 	cmpb   $0x0,0xec50a4(%rip)        # 0xec50da
  36:	0f 85 62 ff ff ff    	jne    0xffffffffffffff9e
  3c:	c6                   	.byte 0xc6
  3d:	05                   	.byte 0x5
  3e:	97                   	xchg   %eax,%edi
  3f:	50                   	push   %rax

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	80 3d a4 50 ec 00 00 	cmpb   $0x0,0xec50a4(%rip)        # 0xec50b0
   c:	0f 85 62 ff ff ff    	jne    0xffffffffffffff74
  12:	c6                   	.byte 0xc6
  13:	05                   	.byte 0x5
  14:	97                   	xchg   %eax,%edi
  15:	50                   	push   %rax
[   13.207465] RSP: 0018:ffffb79240067d50 EFLAGS: 00010286
[   13.207514] RAX: 0000000000000000 RBX: ffffb79240067d60 RCX: 00000000ffffdfff
[   13.207585] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[   13.207657] RBP: ffffb79240067878 R08: ffffffff9fd5ca28 R09: 00000000ffffdfff
[   13.207726] R10: ffffffff9fc7ca40 R11: ffffffff9fd2ca40 R12: dead000000000122
[   13.207795] R13: 00000000fffb9f33 R14: 0000000000000001 R15: ffff9e28453d2000
[   13.207870] FS:  0000000000000000(0000) GS:ffff9e28de7c0000(0000) knlGS:0000000000000000
[   13.207938] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   13.207996] CR2: 000055d2af99d3a8 CR3: 00000000082a7004 CR4: 0000000000772ef0
[   13.208064] PKRU: 55555554
[   13.208091] Call Trace:
[   13.208122]  <TASK>
[   13.208153]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   13.208201]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   13.208241]  cleanup_net (net/core/net_namespace.c:698)
[   13.208279]  process_one_work (kernel/workqueue.c:3268)
[   13.208322]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   13.208361]  ? rescuer_thread (kernel/workqueue.c:3373)
[   13.208400]  kthread (kernel/kthread.c:463)
[   13.208441]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   13.208491]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   13.208540]  ret_from_fork (arch/x86/kernel/process.c:164)
[   13.208582]  ? kthreads_online_cpu (kernel/kthread.c:412)


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