======================================
| [  469.066038] ------------[ cut here ]------------
| [  469.066312] refcount_t: underflow; use-after-free.
| [  469.066597] WARNING: CPU: 0 PID: 10 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  469.067059] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel dummy ip_gre xfrm_user cls_matchall bridge stp llc act_mirred act_police act_gact cls_flower sch_ingress 8021q ip6_gre ip6_tunnel tunnel6 gre vrf veth
[  469.068481] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  469.069094] Workqueue: netns cleanup_net
[  469.069313] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 469.069594] 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 c8 70 cf a4 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 c8 70 cf a4 	mov    $0xffffffffa4cf70c8,%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
[  469.070600] RSP: 0018:ffffa8fdc005bd78 EFLAGS: 00010286
[  469.070889] RAX: 0000000000000000 RBX: ffff9191c2a90000 RCX: 00000000ffffdfff
[  469.071277] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  469.071661] RBP: ffff9191c2a905f8 R08: ffffffffa5164508 R09: 00000000ffffdfff
[  469.072046] R10: ffffffffa5084520 R11: ffffffffa5134520 R12: ffff9191c2a90000
[  469.072424] R13: ffffa8fdc005be08 R14: ffff9191c2a90b60 R15: ffff9191c5338050
[  469.072812] FS:  0000000000000000(0000) GS:ffff9191fec00000(0000) knlGS:0000000000000000
[  469.073247] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  469.073557] CR2: 00007fed3b3f7270 CR3: 0000000012a4c004 CR4: 00000000001706f0
[  469.073940] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  469.074318] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  469.074698] Call Trace:
[  469.074847]  <TASK>
[  469.074974] ? __warn (kernel/panic.c:677) 
[  469.075160] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  469.075416] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  469.075620] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  469.075823] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  469.076036] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  469.076268] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  469.076519] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  469.076776] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) bridge
[  469.077080] br_dev_delete (net/bridge/br_if.c:396) bridge
[  469.077338] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  469.077630] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  469.077835] ? process_one_work (kernel/workqueue.c:2606) 
[  469.078068] process_one_work (kernel/workqueue.c:2638) 
[  469.078291] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  469.078501] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  469.078735] kthread (kernel/kthread.c:388) 
[  469.078918] ? __pfx_kthread (kernel/kthread.c:341) 
[  469.079125] ret_from_fork (arch/x86/kernel/process.c:153) 
[  469.079324] ? __pfx_kthread (kernel/kthread.c:341) 
[  469.079531] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  469.082172] ------------[ cut here ]------------
| [  469.082424] sysfs group 'bridge' not found for kobject 'br3'
| [  469.082748] WARNING: CPU: 0 PID: 10 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  469.083191] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel dummy ip_gre xfrm_user cls_matchall bridge stp llc act_mirred act_police act_gact cls_flower sch_ingress 8021q ip6_gre ip6_tunnel tunnel6 gre vrf veth
[  469.084665] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  469.085276] Workqueue: netns cleanup_net
[  469.085497] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 469.085760] 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 b0 06 cf a4 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 b0 06 cf a4 	mov    $0xffffffffa4cf06b0,%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)
	...
[  469.086746] RSP: 0018:ffffa8fdc005bd70 EFLAGS: 00010286
[  469.087037] RAX: 0000000000000000 RBX: ffffffffc06cbc60 RCX: 00000000ffffdfff
[  469.087414] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  469.087791] RBP: 0000000000000000 R08: ffffffffa5164508 R09: 00000000ffffdfff
[  469.088176] R10: ffffffffa5084520 R11: ffffffffa5134520 R12: ffff9191c2a905f8
[  469.088556] R13: ffffa8fdc005be08 R14: ffff9191c2a90b60 R15: ffff9191c5338050
[  469.088944] FS:  0000000000000000(0000) GS:ffff9191fec00000(0000) knlGS:0000000000000000
[  469.089380] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  469.089692] CR2: 00007fed3b3f7270 CR3: 0000000012a4c004 CR4: 00000000001706f0
[  469.090094] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  469.090480] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  469.090868] Call Trace:
[  469.091010]  <TASK>
[  469.091133] ? __warn (kernel/panic.c:677) 
[  469.091313] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  469.091540] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  469.091744] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  469.091947] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  469.092164] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  469.092398] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  469.092628] br_dev_delete (net/bridge/br_if.c:396) bridge
[  469.092890] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  469.093181] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  469.093384] ? process_one_work (kernel/workqueue.c:2606) 
[  469.093612] process_one_work (kernel/workqueue.c:2638) 
[  469.093840] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  469.094052] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  469.094288] kthread (kernel/kthread.c:388) 
[  469.094465] ? __pfx_kthread (kernel/kthread.c:341) 
[  469.094685] ret_from_fork (arch/x86/kernel/process.c:153) 
[  469.094901] ? __pfx_kthread (kernel/kthread.c:341) 
[  469.095109] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  469.198061] ------------[ cut here ]------------
| [  469.198390] sysfs group 'bridge' not found for kobject 'br3'
| [  469.198766] WARNING: CPU: 2 PID: 10 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  469.199287] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel dummy ip_gre xfrm_user cls_matchall bridge stp llc act_mirred act_police act_gact cls_flower sch_ingress 8021q ip6_gre ip6_tunnel tunnel6 gre vrf veth
[  469.200870] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  469.201556] Workqueue: netns cleanup_net
[  469.201825] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 469.202126] 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 b0 06 cf a4 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 b0 06 cf a4 	mov    $0xffffffffa4cf06b0,%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)
	...
[  469.203178] RSP: 0018:ffffa8fdc005bd70 EFLAGS: 00010286
[  469.203478] RAX: 0000000000000000 RBX: ffffffffc06cbc60 RCX: 00000000ffffdfff
[  469.203868] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  469.204253] RBP: 0000000000000000 R08: ffffffffa5164508 R09: 00000000ffffdfff
[  469.204640] R10: ffffffffa5084520 R11: ffffffffa5134520 R12: ffff9191c26c05f8
[  469.205026] R13: ffffa8fdc005be08 R14: ffff9191c26c0b60 R15: ffffffffa6613dd0
[  469.205407] FS:  0000000000000000(0000) GS:ffff9191fed00000(0000) knlGS:0000000000000000
[  469.205837] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  469.206148] CR2: 000055fa26bd9dec CR3: 0000000003ab4004 CR4: 00000000001706f0
[  469.206527] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  469.206919] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  469.207328] Call Trace:
[  469.207466]  <TASK>
[  469.207588] ? __warn (kernel/panic.c:677) 
[  469.207770] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  469.208013] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  469.208224] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  469.208418] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  469.208626] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  469.208868] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  469.209099] br_dev_delete (net/bridge/br_if.c:396) bridge
[  469.209356] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  469.209645] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  469.209854] ? process_one_work (kernel/workqueue.c:2606) 
[  469.210126] process_one_work (kernel/workqueue.c:2638) 
[  469.210356] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  469.210567] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  469.210811] kthread (kernel/kthread.c:388) 
[  469.210988] ? __pfx_kthread (kernel/kthread.c:341) 
[  469.211223] ret_from_fork (arch/x86/kernel/process.c:153) 
[  469.211425] ? __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