======================================
| xx__-> [   12.730044] ------------[ cut here ]------------
| [   12.730116] refcount_t: underflow; use-after-free.
| [   12.730180] WARNING: CPU: 0 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   12.730254] Modules linked in: tcp_diag mptcp_diag inet_diag
[   12.730390] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   12.730446] Workqueue: netns cleanup_net
[   12.730486] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   12.730532] Code: a1 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 b2 a1 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:	a1 e8 48 df ba ff 90 	movabs 0xb0f90ffbadf48e8,%eax
   7:	0f 0b 
   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 b2 a1 	mov    $0xffffffffa1b24ac8,%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
[   12.730687] RSP: 0018:ffffa0bf80067d50 EFLAGS: 00010286
[   12.730731] RAX: 0000000000000000 RBX: ffffa0bf80067d60 RCX: 00000000ffffdfff
[   12.730802] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[   12.730866] RBP: ffffa0bf80067878 R08: ffffffffa1f5ca28 R09: 00000000ffffdfff
[   12.730934] R10: ffffffffa1e7ca40 R11: ffffffffa1f2ca40 R12: dead000000000122
[   12.730993] R13: 00000000fffb9d53 R14: 0000000000000001 R15: ffff958201c9c000
[   12.731076] FS:  0000000000000000(0000) GS:ffff95829c5c0000(0000) knlGS:0000000000000000
[   12.731148] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   12.731202] CR2: 0000563d5146a3b8 CR3: 0000000004b4b001 CR4: 0000000000772ef0
[   12.731266] PKRU: 55555554
[   12.731290] Call Trace:
[   12.731327]  <TASK>
[   12.731352]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   12.731399]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   12.731440]  cleanup_net (net/core/net_namespace.c:698)
[   12.731476]  process_one_work (kernel/workqueue.c:3268)
[   12.731514]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   12.731550]  ? rescuer_thread (kernel/workqueue.c:3373)
[   12.731586]  kthread (kernel/kthread.c:463)
[   12.731628]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   12.731672]  ? kthreads_online_cpu (kernel/kthread.c:412)
[   12.731717]  ret_from_fork (arch/x86/kernel/process.c:164)
[   12.731759]  ? kthreads_online_cpu (kernel/kthread.c:412)


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