======================================
| [  150.166646] ------------[ cut here ]------------
| [  150.167059] refcount_t: underflow; use-after-free.
| [  150.167505] WARNING: CPU: 2 PID: 67 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [  150.168141] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel sch_tbf 8021q act_mirred cls_flower bridge stp llc ip6_gre ip6_tunnel tunnel6 act_gact cls_matchall ip_gre gre sch_ingress vrf veth
[  150.169510] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  150.170129] Workqueue: netns cleanup_net
[  150.170370] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 150.170749] 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 6f 98 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 6f 98 	mov    $0xffffffff986f70c8,%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
[  150.171847] RSP: 0018:ffffafcd4025bd78 EFLAGS: 00010286
[  150.172260] RAX: 0000000000000000 RBX: ffff8eeb0209e000 RCX: 00000000ffffdfff
[  150.172870] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  150.173286] RBP: ffff8eeb0209e5f8 R08: ffffffff98b64508 R09: 00000000ffffdfff
[  150.173678] R10: ffffffff98a84520 R11: ffffffff98b34520 R12: ffff8eeb0209e000
[  150.174058] R13: ffffafcd4025be08 R14: ffff8eeb0209eb60 R15: ffff8eeb03860050
[  150.174474] FS:  0000000000000000(0000) GS:ffff8eeb3ed00000(0000) knlGS:0000000000000000
[  150.175046] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  150.175474] CR2: 000055cd4e56ec70 CR3: 000000000271c004 CR4: 00000000001706f0
[  150.175985] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  150.176498] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  150.176935] Call Trace:
[  150.177073]  <TASK>
[  150.177196] ? __warn (kernel/panic.c:677) 
[  150.177394] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  150.177650] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  150.177871] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  150.178084] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  150.178325] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  150.178578] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  150.178850] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[  150.179124] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) bridge
[  150.179467] br_dev_delete (net/bridge/br_if.c:396) bridge
[  150.179761] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  150.180092] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  150.180373] ? process_one_work (kernel/workqueue.c:2606) 
[  150.180700] process_one_work (kernel/workqueue.c:2638) 
[  150.181017] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  150.181328] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  150.181664] kthread (kernel/kthread.c:388) 
[  150.181920] ? __pfx_kthread (kernel/kthread.c:341) 
[  150.182221] ret_from_fork (arch/x86/kernel/process.c:153) 
[  150.182514] ? __pfx_kthread (kernel/kthread.c:341) 
[  150.182795] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  150.186253] ------------[ cut here ]------------
| [  150.186597] sysfs group 'bridge' not found for kobject 'br2'
| [  150.186969] WARNING: CPU: 2 PID: 67 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  150.187420] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel sch_tbf 8021q act_mirred cls_flower bridge stp llc ip6_gre ip6_tunnel tunnel6 act_gact cls_matchall ip_gre gre sch_ingress vrf veth
[  150.188856] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  150.189477] Workqueue: netns cleanup_net
[  150.189699] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 150.189995] 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 6f 98 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 6f 98 	mov    $0xffffffff986f06b0,%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)
	...
[  150.191319] RSP: 0018:ffffafcd4025bd70 EFLAGS: 00010286
[  150.191606] RAX: 0000000000000000 RBX: ffffffffc0424c60 RCX: 00000000ffffdfff
[  150.191986] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  150.192389] RBP: 0000000000000000 R08: ffffffff98b64508 R09: 00000000ffffdfff
[  150.192774] R10: ffffffff98a84520 R11: ffffffff98b34520 R12: ffff8eeb0209e5f8
[  150.193200] R13: ffffafcd4025be08 R14: ffff8eeb0209eb60 R15: ffff8eeb03860050
[  150.193605] FS:  0000000000000000(0000) GS:ffff8eeb3ed00000(0000) knlGS:0000000000000000
[  150.194034] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  150.194362] CR2: 000055cd4e56ec70 CR3: 000000000271c004 CR4: 00000000001706f0
[  150.194748] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  150.195137] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  150.195532] Call Trace:
[  150.195671]  <TASK>
[  150.195798] ? __warn (kernel/panic.c:677) 
[  150.195985] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  150.196221] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  150.196440] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  150.196638] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  150.196861] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  150.197158] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  150.197503] br_dev_delete (net/bridge/br_if.c:396) bridge
[  150.197793] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  150.198171] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  150.198445] ? process_one_work (kernel/workqueue.c:2606) 
[  150.198745] process_one_work (kernel/workqueue.c:2638) 
[  150.199060] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  150.199369] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  150.199708] kthread (kernel/kthread.c:388) 
[  150.199962] ? __pfx_kthread (kernel/kthread.c:341) 
[  150.200260] ret_from_fork (arch/x86/kernel/process.c:153) 
[  150.200559] ? __pfx_kthread (kernel/kthread.c:341) 
[  150.200841] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [  150.304496] ------------[ cut here ]------------
| [  150.304775] sysfs group 'bridge' not found for kobject 'br2'
| [  150.305103] WARNING: CPU: 3 PID: 67 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [  150.305598] Modules linked in: vxlan ip6_udp_tunnel udp_tunnel sch_tbf 8021q act_mirred cls_flower bridge stp llc ip6_gre ip6_tunnel tunnel6 act_gact cls_matchall ip_gre gre sch_ingress vrf veth
[  150.307017] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[  150.307640] Workqueue: netns cleanup_net
[  150.307862] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 150.308131] 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 6f 98 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 6f 98 	mov    $0xffffffff986f06b0,%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)
	...
[  150.309124] RSP: 0018:ffffafcd4025bd70 EFLAGS: 00010286
[  150.309450] RAX: 0000000000000000 RBX: ffffffffc0424c60 RCX: 00000000ffffdfff
[  150.309842] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[  150.310234] RBP: 0000000000000000 R08: ffffffff98b64508 R09: 00000000ffffdfff
[  150.310631] R10: ffffffff98a84520 R11: ffffffff98b34520 R12: ffff8eeb05c7c5f8
[  150.311025] R13: ffffafcd4025be08 R14: ffff8eeb05c7cb60 R15: ffffffff9a013dd0
[  150.311419] FS:  0000000000000000(0000) GS:ffff8eeb3ed80000(0000) knlGS:0000000000000000
[  150.311853] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  150.312169] CR2: 0000557df44a8dec CR3: 00000000018b8001 CR4: 00000000001706f0
[  150.312593] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  150.313023] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  150.313454] Call Trace:
[  150.313605]  <TASK>
[  150.313734] ? __warn (kernel/panic.c:677) 
[  150.313943] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  150.314198] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[  150.314430] ? handle_bug (arch/x86/kernel/traps.c:238) 
[  150.314653] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[  150.314896] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[  150.315156] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[  150.315412] br_dev_delete (net/bridge/br_if.c:396) bridge
[  150.315696] br_net_exit_batch_rtnl (net/bridge/br.c:369) bridge
[  150.316010] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[  150.316235] ? process_one_work (kernel/workqueue.c:2606) 
[  150.316498] process_one_work (kernel/workqueue.c:2638) 
[  150.316742] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[  150.316970] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[  150.317245] kthread (kernel/kthread.c:388) 
[  150.317462] ? __pfx_kthread (kernel/kthread.c:341) 
[  150.317701] ret_from_fork (arch/x86/kernel/process.c:153) 
[  150.317921] ? __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