======================================
| [  390.331149] ------------[ cut here ]------------
| [  390.331419] refcount_t: underflow; use-after-free.
| [  390.331715] WARNING: CPU: 0 PID: 11 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  390.332169] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel sch_tbf sch_prio bridge stp llc act_gact cls_flower sch_ingress 8021q ip_gre gre vrf veth
[  390.333311] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  390.333928] Workqueue: netns cleanup_net
[  390.334158] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 390.334450] Code: 0b 90 90 c3 cc cc cc cc 80 3d a1 b9 66 01 00 0f 85 75 ff ff ff c6 05 94 b9 66 01 01 90 48 c7 c7 a0 70 2f ab e8 71 92 b4 ff 90 <0f> 0b 90 90 c3 cc cc cc cc 80 3d 74 b9 66 01 00 0f 85 4a ff ff ff
All code
========
   0:	0b 90 90 c3 cc cc    	or     -0x33333c70(%rax),%edx
   6:	cc                   	int3
   7:	cc                   	int3
   8:	80 3d a1 b9 66 01 00 	cmpb   $0x0,0x166b9a1(%rip)        # 0x166b9b0
   f:	0f 85 75 ff ff ff    	jne    0xffffffffffffff8a
  15:	c6 05 94 b9 66 01 01 	movb   $0x1,0x166b994(%rip)        # 0x166b9b0
  1c:	90                   	nop
  1d:	48 c7 c7 a0 70 2f ab 	mov    $0xffffffffab2f70a0,%rdi
  24:	e8 71 92 b4 ff       	call   0xffffffffffb4929a
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	c3                   	ret
  2f:	cc                   	int3
  30:	cc                   	int3
  31:	cc                   	int3
  32:	cc                   	int3
  33:	80 3d 74 b9 66 01 00 	cmpb   $0x0,0x166b974(%rip)        # 0x166b9ae
  3a:	0f 85 4a ff ff ff    	jne    0xffffffffffffff8a

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	c3                   	ret
   5:	cc                   	int3
   6:	cc                   	int3
   7:	cc                   	int3
   8:	cc                   	int3
   9:	80 3d 74 b9 66 01 00 	cmpb   $0x0,0x166b974(%rip)        # 0x166b984
  10:	0f 85 4a ff ff ff    	jne    0xffffffffffffff60
[  390.335435] RSP: 0018:ffffbb66c0063d78 EFLAGS: 00010286
[  390.335724] RAX: 0000000000000000 RBX: ffff902ac190a000 RCX: 00000000ffffdfff
[  390.336115] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  390.336504] RBP: ffff902ac190a5f8 R08: ffffffffab764508 R09: 00000000ffffdfff
[  390.336883] R10: ffffffffab684520 R11: ffffffffab734520 R12: ffff902ac190a000
[  390.337274] R13: ffffbb66c0063e08 R14: ffff902ac190ab60 R15: ffff902ac1bd8050
[  390.337658] FS:  0000000000000000(0000) GS:ffff902afec00000(0000) knlGS:0000000000000000
[  390.338091] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  390.338407] CR2: 00007f6e72398270 CR3: 0000000001c08003 CR4: 00000000001706f0
[  390.338799] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  390.339187] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  390.339574] Call Trace:
[  390.339713]  <TASK>
[  390.339840] ? __warn (kernel/panic.c:677) 
[  390.340030] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  390.340283] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  390.340498] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  390.340710] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  390.340917] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  390.341155] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  390.341406] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  390.341675] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) bridge
[  390.341985] br_dev_delete (net/bridge/br_if.c:396) bridge
[  390.342238] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  390.342535] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  390.342739] ? process_one_work (kernel/workqueue.c:2606) 
[  390.342976] process_one_work (kernel/workqueue.c:2638) 
[  390.343199] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  390.343411] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  390.343653] kthread (kernel/kthread.c:388) 
[  390.343833] ? __pfx_kthread (kernel/kthread.c:341) 
[  390.344050] ret_from_fork (arch/x86/kernel/process.c:153) 
[  390.344248] ? __pfx_kthread (kernel/kthread.c:341) 
[  390.344468] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  390.347071] ------------[ cut here ]------------
| [  390.347323] sysfs group 'bridge' not found for kobject 'br2'
| [  390.347658] WARNING: CPU: 0 PID: 11 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  390.348300] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel sch_tbf sch_prio bridge stp llc act_gact cls_flower sch_ingress 8021q ip_gre gre vrf veth
[  390.349526] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  390.350133] Workqueue: netns cleanup_net
[  390.350351] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 390.350624] Code: 48 89 ef 5d 41 5c e9 0a ae ff ff 48 89 ef e8 a2 9b ff ff eb d1 90 49 8b 14 24 48 8b 33 48 c7 c7 88 06 2f ab e8 fc b0 c5 ff 90 <0f> 0b 90 90 5b 5d 41 5c c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00
All code
========
   0:	48 89 ef             	mov    %rbp,%rdi
   3:	5d                   	pop    %rbp
   4:	41 5c                	pop    %r12
   6:	e9 0a ae ff ff       	jmp    0xffffffffffffae15
   b:	48 89 ef             	mov    %rbp,%rdi
   e:	e8 a2 9b ff ff       	call   0xffffffffffff9bb5
  13:	eb d1                	jmp    0xffffffffffffffe6
  15:	90                   	nop
  16:	49 8b 14 24          	mov    (%r12),%rdx
  1a:	48 8b 33             	mov    (%rbx),%rsi
  1d:	48 c7 c7 88 06 2f ab 	mov    $0xffffffffab2f0688,%rdi
  24:	e8 fc b0 c5 ff       	call   0xffffffffffc5b125
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	5b                   	pop    %rbx
  2f:	5d                   	pop    %rbp
  30:	41 5c                	pop    %r12
  32:	c3                   	ret
  33:	cc                   	int3
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	66                   	data16
  38:	66                   	data16
  39:	2e                   	cs
  3a:	0f                   	.byte 0xf
  3b:	1f                   	(bad)
  3c:	84 00                	test   %al,(%rax)
	...

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	5b                   	pop    %rbx
   5:	5d                   	pop    %rbp
   6:	41 5c                	pop    %r12
   8:	c3                   	ret
   9:	cc                   	int3
   a:	cc                   	int3
   b:	cc                   	int3
   c:	cc                   	int3
   d:	66                   	data16
   e:	66                   	data16
   f:	2e                   	cs
  10:	0f                   	.byte 0xf
  11:	1f                   	(bad)
  12:	84 00                	test   %al,(%rax)
	...
[  390.351608] RSP: 0018:ffffbb66c0063d70 EFLAGS: 00010286
[  390.351900] RAX: 0000000000000000 RBX: ffffffffc050bc60 RCX: 00000000ffffdfff
[  390.352281] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  390.352670] RBP: 0000000000000000 R08: ffffffffab764508 R09: 00000000ffffdfff
[  390.353056] R10: ffffffffab684520 R11: ffffffffab734520 R12: ffff902ac190a5f8
[  390.353442] R13: ffffbb66c0063e08 R14: ffff902ac190ab60 R15: ffff902ac1bd8050
[  390.353825] FS:  0000000000000000(0000) GS:ffff902afec00000(0000) knlGS:0000000000000000
[  390.354261] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  390.354576] CR2: 00007f6e72398270 CR3: 0000000001c08003 CR4: 00000000001706f0
[  390.354960] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  390.355340] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  390.355732] Call Trace:
[  390.355878]  <TASK>
[  390.356008] ? __warn (kernel/panic.c:677) 
[  390.356190] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  390.356423] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  390.356634] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  390.356829] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  390.357051] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  390.357289] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  390.357526] br_dev_delete (net/bridge/br_if.c:396) bridge
[  390.357792] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  390.358089] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  390.358289] ? process_one_work (kernel/workqueue.c:2606) 
[  390.358531] process_one_work (kernel/workqueue.c:2638) 
[  390.358754] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  390.358972] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  390.359205] kthread (kernel/kthread.c:388) 
[  390.359383] ? __pfx_kthread (kernel/kthread.c:341) 
[  390.359599] ret_from_fork (arch/x86/kernel/process.c:153) 
[  390.359796] ? __pfx_kthread (kernel/kthread.c:341) 
[  390.360016] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  390.496134] ------------[ cut here ]------------
| [  390.496397] sysfs group 'bridge' not found for kobject 'br2'
| [  390.496736] WARNING: CPU: 2 PID: 11 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  390.497192] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel sch_tbf sch_prio bridge stp llc act_gact cls_flower sch_ingress 8021q ip_gre gre vrf veth
[  390.498447] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  390.499074] Workqueue: netns cleanup_net
[  390.499300] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 390.499563] Code: 48 89 ef 5d 41 5c e9 0a ae ff ff 48 89 ef e8 a2 9b ff ff eb d1 90 49 8b 14 24 48 8b 33 48 c7 c7 88 06 2f ab e8 fc b0 c5 ff 90 <0f> 0b 90 90 5b 5d 41 5c c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00
All code
========
   0:	48 89 ef             	mov    %rbp,%rdi
   3:	5d                   	pop    %rbp
   4:	41 5c                	pop    %r12
   6:	e9 0a ae ff ff       	jmp    0xffffffffffffae15
   b:	48 89 ef             	mov    %rbp,%rdi
   e:	e8 a2 9b ff ff       	call   0xffffffffffff9bb5
  13:	eb d1                	jmp    0xffffffffffffffe6
  15:	90                   	nop
  16:	49 8b 14 24          	mov    (%r12),%rdx
  1a:	48 8b 33             	mov    (%rbx),%rsi
  1d:	48 c7 c7 88 06 2f ab 	mov    $0xffffffffab2f0688,%rdi
  24:	e8 fc b0 c5 ff       	call   0xffffffffffc5b125
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	5b                   	pop    %rbx
  2f:	5d                   	pop    %rbp
  30:	41 5c                	pop    %r12
  32:	c3                   	ret
  33:	cc                   	int3
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	66                   	data16
  38:	66                   	data16
  39:	2e                   	cs
  3a:	0f                   	.byte 0xf
  3b:	1f                   	(bad)
  3c:	84 00                	test   %al,(%rax)
	...

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	5b                   	pop    %rbx
   5:	5d                   	pop    %rbp
   6:	41 5c                	pop    %r12
   8:	c3                   	ret
   9:	cc                   	int3
   a:	cc                   	int3
   b:	cc                   	int3
   c:	cc                   	int3
   d:	66                   	data16
   e:	66                   	data16
   f:	2e                   	cs
  10:	0f                   	.byte 0xf
  11:	1f                   	(bad)
  12:	84 00                	test   %al,(%rax)
	...
[  390.500567] RSP: 0018:ffffbb66c0063d70 EFLAGS: 00010286
[  390.500849] RAX: 0000000000000000 RBX: ffffffffc050bc60 RCX: 00000000ffffdfff
[  390.501241] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  390.501619] RBP: 0000000000000000 R08: ffffffffab764508 R09: 00000000ffffdfff
[  390.502053] R10: ffffffffab684520 R11: ffffffffab734520 R12: ffff902ac24d65f8
[  390.502445] R13: ffffbb66c0063e08 R14: ffff902ac24d6b60 R15: ffffffffacc13dd0
[  390.502854] FS:  0000000000000000(0000) GS:ffff902afed00000(0000) knlGS:0000000000000000
[  390.503301] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  390.503610] CR2: 00007f3bcaa351b4 CR3: 000000000f44c005 CR4: 00000000001706f0
[  390.504001] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  390.504420] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  390.504804] Call Trace:
[  390.504957]  <TASK>
[  390.505079] ? __warn (kernel/panic.c:677) 
[  390.505263] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  390.505502] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  390.505714] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  390.505916] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  390.506143] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  390.506379] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  390.506616] br_dev_delete (net/bridge/br_if.c:396) bridge
[  390.506889] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  390.507202] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  390.507413] ? process_one_work (kernel/workqueue.c:2606) 
[  390.507644] process_one_work (kernel/workqueue.c:2638) 
[  390.507881] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  390.508104] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  390.508368] kthread (kernel/kthread.c:388) 
[  390.508551] ? __pfx_kthread (kernel/kthread.c:341) 
[  390.508760] ret_from_fork (arch/x86/kernel/process.c:153) 
[  390.508969] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
refcount_warn_saturate:br_sysfs_delbr:br_dev_delete:br_net_exit_batch_rtnl
sysfs_remove_group:br_dev_delete:br_net_exit_batch_rtnl:cleanup_net
sysfs_remove_group:br_dev_delete:br_net_exit_batch_rtnl:cleanup_net