======================================
| [    2.690808] ------------[ cut here ]------------
| [    2.690900] refcount_t: underflow; use-after-free.
| [    2.690970] WARNING: CPU: 2 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [    2.691047] Modules linked in:
[    2.691195] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    2.691261] Workqueue: netns cleanup_net
[    2.691334] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[    2.691391] Code: 88 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 12 88 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:	88 e8                	mov    %ch,%al
   2:	48 df ba ff 90 0f 0b 	rex.W fistpll 0xb0f90ff(%rdx)
   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 12 88 	mov    $0xffffffff88124ac8,%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
[    2.691541] RSP: 0018:ffffa79ac0067d50 EFLAGS: 00010286
[    2.691596] RAX: 0000000000000000 RBX: ffffa79ac0067d60 RCX: 00000000ffffdfff
[    2.691685] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[    2.691759] RBP: ffffa79ac0067878 R08: ffffffff8855ca28 R09: 00000000ffffdfff
[    2.691848] R10: ffffffff8847ca40 R11: ffffffff8852ca40 R12: dead000000000122
[    2.691937] R13: 00000000fffb762b R14: 0000000000000001 R15: ffff98df8112e000
[    2.692010] FS:  0000000000000000(0000) GS:ffff98e0360c0000(0000) knlGS:0000000000000000
[    2.692086] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.692152] CR2: 00007ff44f400000 CR3: 000000001e047002 CR4: 0000000000772ef0
[    2.692226] PKRU: 55555554
[    2.692283] Call Trace:
[    2.692338]  <TASK>
[    2.692400]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[    2.692453]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[    2.692502]  cleanup_net (net/core/net_namespace.c:698)
[    2.692550]  process_one_work (kernel/workqueue.c:3268)
[    2.692604]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[    2.692654]  ? rescuer_thread (kernel/workqueue.c:3373)
[    2.692702]  kthread (kernel/kthread.c:463)
[    2.692771]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    2.692851]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    2.692908]  ret_from_fork (arch/x86/kernel/process.c:164)
[    2.692977]  ? kthreads_online_cpu (kernel/kthread.c:412)


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