======================================
| [  829.165353] ------------[ cut here ]------------
| [  829.165653] refcount_t: underflow; use-after-free.
| [  829.165959] WARNING: CPU: 2 PID: 67 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  829.166459] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel bridge stp llc act_gact cls_flower sch_ingress 8021q ip_gre gre vrf veth
[  829.167595] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  829.168206] Workqueue: netns cleanup_net
[  829.168429] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 829.168718] 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 8f 88 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 8f 88 	mov    $0xffffffff888f70a0,%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
[  829.169696] RSP: 0018:ffffb6d74025bd78 EFLAGS: 00010286
[  829.169981] RAX: 0000000000000000 RBX: ffff8edc026d8000 RCX: 00000000ffffdfff
[  829.170374] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  829.170754] RBP: ffff8edc026d85f8 R08: ffffffff88d64508 R09: 00000000ffffdfff
[  829.171140] R10: ffffffff88c84520 R11: ffffffff88d34520 R12: ffff8edc026d8000
[  829.171517] R13: ffffb6d74025be08 R14: ffff8edc026d8b60 R15: ffff8edc018a8050
[  829.171892] FS:  0000000000000000(0000) GS:ffff8edc3ed00000(0000) knlGS:0000000000000000
[  829.172321] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  829.172636] CR2: 0000557cc0806eb8 CR3: 0000000030c4c005 CR4: 00000000001706f0
[  829.173024] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  829.173410] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  829.173788] Call Trace:
[  829.173926]  <TASK>
[  829.174048] ? __warn (kernel/panic.c:677) 
[  829.174239] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  829.174492] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  829.174703] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  829.174901] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  829.175119] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  829.175357] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  829.175610] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  829.175859] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) bridge
[  829.176162] br_dev_delete (net/bridge/br_if.c:396) bridge
[  829.176413] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  829.176700] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  829.176904] ? process_one_work (kernel/workqueue.c:2606) 
[  829.177147] process_one_work (kernel/workqueue.c:2638) 
[  829.177375] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  829.177587] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  829.177822] kthread (kernel/kthread.c:388) 
[  829.178005] ? __pfx_kthread (kernel/kthread.c:341) 
[  829.178221] ret_from_fork (arch/x86/kernel/process.c:153) 
[  829.178435] ? __pfx_kthread (kernel/kthread.c:341) 
[  829.178656] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  829.181419] ------------[ cut here ]------------
| [  829.181692] sysfs group 'bridge' not found for kobject 'br2'
| [  829.182040] WARNING: CPU: 2 PID: 67 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  829.182509] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel bridge stp llc act_gact cls_flower sch_ingress 8021q ip_gre gre vrf veth
[  829.183705] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  829.184359] Workqueue: netns cleanup_net
[  829.184594] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 829.184872] 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 8f 88 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 8f 88 	mov    $0xffffffff888f0688,%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)
	...
[  829.185847] RSP: 0018:ffffb6d74025bd70 EFLAGS: 00010286
[  829.186136] RAX: 0000000000000000 RBX: ffffffffc042ac60 RCX: 00000000ffffdfff
[  829.186521] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  829.186893] RBP: 0000000000000000 R08: ffffffff88d64508 R09: 00000000ffffdfff
[  829.187284] R10: ffffffff88c84520 R11: ffffffff88d34520 R12: ffff8edc026d85f8
[  829.187700] R13: ffffb6d74025be08 R14: ffff8edc026d8b60 R15: ffff8edc018a8050
[  829.188102] FS:  0000000000000000(0000) GS:ffff8edc3ed00000(0000) knlGS:0000000000000000
[  829.188568] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  829.188902] CR2: 0000557cc0806eb8 CR3: 0000000030c4c005 CR4: 00000000001706f0
[  829.189320] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  829.189726] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  829.190141] Call Trace:
[  829.190292]  <TASK>
[  829.190420] ? __warn (kernel/panic.c:677) 
[  829.190612] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  829.190867] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  829.191089] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  829.191313] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  829.191540] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  829.191793] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  829.192040] br_dev_delete (net/bridge/br_if.c:396) bridge
[  829.192329] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  829.192647] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  829.192862] ? process_one_work (kernel/workqueue.c:2606) 
[  829.193105] process_one_work (kernel/workqueue.c:2638) 
[  829.193356] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  829.193581] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  829.193827] kthread (kernel/kthread.c:388) 
[  829.194020] ? __pfx_kthread (kernel/kthread.c:341) 
[  829.194242] ret_from_fork (arch/x86/kernel/process.c:153) 
[  829.194461] ? __pfx_kthread (kernel/kthread.c:341) 
[  829.194693] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  829.310400] ------------[ cut here ]------------
| [  829.310792] sysfs group 'bridge' not found for kobject 'br2'
| [  829.311297] WARNING: CPU: 2 PID: 67 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  829.311949] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel bridge stp llc act_gact cls_flower sch_ingress 8021q ip_gre gre vrf veth
[  829.313639] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  829.314558] Workqueue: netns cleanup_net
[  829.314889] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 829.315281] 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 8f 88 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 8f 88 	mov    $0xffffffff888f0688,%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)
	...
[  829.316474] RSP: 0018:ffffb6d74025bd70 EFLAGS: 00010286
[  829.316756] RAX: 0000000000000000 RBX: ffffffffc042ac60 RCX: 00000000ffffdfff
[  829.317166] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  829.317546] RBP: 0000000000000000 R08: ffffffff88d64508 R09: 00000000ffffdfff
[  829.317927] R10: ffffffff88c84520 R11: ffffffff88d34520 R12: ffff8edc026625f8
[  829.318305] R13: ffffb6d74025be08 R14: ffff8edc02662b60 R15: ffffffff8a213dd0
[  829.318683] FS:  0000000000000000(0000) GS:ffff8edc3ed00000(0000) knlGS:0000000000000000
[  829.319119] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  829.319423] CR2: 0000557cc0806eb8 CR3: 0000000030c4c005 CR4: 00000000001706f0
[  829.319814] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  829.320200] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  829.320580] Call Trace:
[  829.320724]  <TASK>
[  829.320854] ? __warn (kernel/panic.c:677) 
[  829.321038] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  829.321274] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  829.321482] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  829.321676] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  829.321890] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  829.322130] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  829.322360] br_dev_delete (net/bridge/br_if.c:396) bridge
[  829.322624] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  829.322916] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  829.323127] ? process_one_work (kernel/workqueue.c:2606) 
[  829.323358] process_one_work (kernel/workqueue.c:2638) 
[  829.323577] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  829.323798] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  829.324099] kthread (kernel/kthread.c:388) 
[  829.324347] ? __pfx_kthread (kernel/kthread.c:341) 
[  829.324648] ret_from_fork (arch/x86/kernel/process.c:153) 
[  829.324895] ? __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