======================================
| [ 2285.937622][   T11] ==================================================================
| [ 2285.938066][ T11] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:729) 
| [ 2285.938515][   T11] Read of size 1 at addr ffff8880051a6bbc by task kworker/u8:0/11
| [ 2285.938923][   T11]
[ 2285.939476][   T11] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 2285.940114][   T11] Workqueue: netns cleanup_net
[ 2285.940374][   T11] Call Trace:
[ 2285.940554][   T11]  <TASK>
[ 2285.940712][ T11] dump_stack_lvl (lib/dump_stack.c:107) 
[ 2285.940963][ T11] print_address_description.constprop.0 (mm/kasan/report.c:378) 
[ 2285.941319][ T11] ? kobject_put (lib/kobject.c:729) 
[ 2285.941557][ T11] print_report (mm/kasan/report.c:489) 
[ 2285.941791][ T11] ? kasan_addr_to_slab (./arch/x86/include/asm/bitops.h:206 ./arch/x86/include/asm/bitops.h:238 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 ./include/linux/page-flags.h:481 mm/kasan/../slab.h:206 mm/kasan/common.c:38) 
[ 2285.942063][ T11] kasan_report (mm/kasan/report.c:603) 
[ 2285.942294][ T11] ? kobject_put (lib/kobject.c:729) 
[ 2285.942535][ T11] kobject_put (lib/kobject.c:729) 
[ 2285.942781][ T11] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) 
[ 2285.943027][ T11] br_dev_delete (net/bridge/br_if.c:396) 
[ 2285.943346][ T11] br_net_exit_batch_rtnl (net/bridge/br.c:369) 
[ 2285.943674][ T11] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[ 2285.943915][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 2285.944243][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:581) 
[ 2285.944536][ T11] ? lock_acquire (./include/trace/events/lock.h:24 kernel/locking/lockdep.c:5725) 
[ 2285.944802][ T11] ? process_one_work (kernel/workqueue.c:2609) 
[ 2285.945081][ T11] process_one_work (kernel/workqueue.c:2638) 
[ 2285.945371][ T11] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:228) 
[ 2285.945638][ T11] ? __pfx_process_one_work (kernel/workqueue.c:2542) 
[ 2285.945955][ T11] ? assign_work (kernel/workqueue.c:1101) 
[ 2285.946224][ T11] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[ 2285.946500][ T11] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[ 2285.946793][ T11] kthread (kernel/kthread.c:388) 
[ 2285.947036][ T11] ? __pfx_kthread (kernel/kthread.c:341) 
[ 2285.947304][ T11] ret_from_fork (arch/x86/kernel/process.c:153) 
[ 2285.947580][ T11] ? __pfx_kthread (kernel/kthread.c:341) 
[ 2285.947850][ T11] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [ 2285.968170][   T11] ------------[ cut here ]------------
| [ 2285.968480][   T11] refcount_t: underflow; use-after-free.
| [ 2285.968834][ T11] WARNING: CPU: 1 PID: 11 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
| [ 2285.969943][   T11] Modules linked in: xfrm_user psample macsec fou ip6_gre ip_gre gre cls_u32 sch_htb xt_mark sch_ingress act_mirred cls_basic sch_fq_codel nft_compat nf_tables libcrc32c vxlan ip6_udp_tunnel udp_tunnel mpls_iptunnel mpls_router [last unloaded: netdevsim]
[ 2285.972198][   T11] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 2285.973096][   T11] Workqueue: netns cleanup_net
[ 2285.973374][ T11] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 2285.973751][ T11] Code: f9 82 03 80 fb 01 0f 87 ee 02 b1 01 83 e3 01 0f 85 4d ff ff ff c6 05 9a f9 82 03 01 90 48 c7 c7 20 7a 62 b7 e8 3e 05 2a ff 90 <0f> 0b 90 90 e9 2f ff ff ff 48 89 df e8 8c 68 a6 ff e9 b6 fe ff ff
All code
========
   0:	f9                   	stc
   1:	82                   	(bad)
   2:	03 80 fb 01 0f 87    	add    -0x78f0fe05(%rax),%eax
   8:	ee                   	out    %al,(%dx)
   9:	02 b1 01 83 e3 01    	add    0x1e38301(%rcx),%dh
   f:	0f 85 4d ff ff ff    	jne    0xffffffffffffff62
  15:	c6 05 9a f9 82 03 01 	movb   $0x1,0x382f99a(%rip)        # 0x382f9b6
  1c:	90                   	nop
  1d:	48 c7 c7 20 7a 62 b7 	mov    $0xffffffffb7627a20,%rdi
  24:	e8 3e 05 2a ff       	call   0xffffffffff2a0567
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	e9 2f ff ff ff       	jmp    0xffffffffffffff62
  33:	48 89 df             	mov    %rbx,%rdi
  36:	e8 8c 68 a6 ff       	call   0xffffffffffa668c7
  3b:	e9 b6 fe ff ff       	jmp    0xfffffffffffffef6

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	e9 2f ff ff ff       	jmp    0xffffffffffffff38
   9:	48 89 df             	mov    %rbx,%rdi
   c:	e8 8c 68 a6 ff       	call   0xffffffffffa6689d
  11:	e9 b6 fe ff ff       	jmp    0xfffffffffffffecc
[ 2285.974876][   T11] RSP: 0018:ffffc900000bfb98 EFLAGS: 00010282
[ 2285.975278][   T11] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffb491056f
[ 2285.975756][   T11] RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000001
[ 2285.976268][   T11] RBP: 0000000000000003 R08: 0000000000000000 R09: fffff52000017f18
[ 2285.976686][   T11] R10: ffffc900000bf8c7 R11: 205d313154202020 R12: ffff8880059fa000
[ 2285.977149][   T11] R13: ffff8880059fadf8 R14: ffffc900000bfc98 R15: ffff8880059fabc0
[ 2285.977570][   T11] FS:  0000000000000000(0000) GS:ffff888035600000(0000) knlGS:0000000000000000
[ 2285.978133][   T11] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2285.978533][   T11] CR2: 00007fff0141cff8 CR3: 0000000006d4a001 CR4: 00000000001706f0
[ 2285.979001][   T11] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2285.979424][   T11] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2285.979843][   T11] Call Trace:
[ 2285.980115][   T11]  <TASK>
[ 2285.980273][ T11] ? __warn (kernel/panic.c:677) 
[ 2285.980545][ T11] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 2285.980873][ T11] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[ 2285.981197][ T11] ? vprintk_emit (kernel/printk/printk.c:2313) 
[ 2285.981474][ T11] ? handle_bug (arch/x86/kernel/traps.c:238) 
[ 2285.981722][ T11] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[ 2285.982051][ T11] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[ 2285.982323][ T11] ? desc_read (./arch/x86/include/asm/atomic64_64.h:20 ./include/linux/atomic/atomic-arch-fallback.h:2615 ./include/linux/atomic/atomic-long.h:79 ./include/linux/atomic/atomic-instrumented.h:3196 kernel/printk/printk_ringbuffer.c:534) 
[ 2285.982562][ T11] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 2285.982852][ T11] ? refcount_warn_saturate (lib/refcount.c:28 (discriminator 3)) 
[ 2285.983197][ T11] br_sysfs_delbr (net/bridge/br_sysfs_br.c:1086) 
[ 2285.983438][ T11] br_dev_delete (net/bridge/br_if.c:396) 
[ 2285.983683][ T11] br_net_exit_batch_rtnl (net/bridge/br.c:369) 
[ 2285.984054][ T11] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[ 2285.984293][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 2285.984588][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:581) 
[ 2285.984854][ T11] ? lock_acquire (./include/trace/events/lock.h:24 kernel/locking/lockdep.c:5725) 
[ 2285.985151][ T11] ? process_one_work (kernel/workqueue.c:2609) 
[ 2285.985424][ T11] process_one_work (kernel/workqueue.c:2638) 
[ 2285.985690][ T11] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:228) 
[ 2285.985979][ T11] ? __pfx_process_one_work (kernel/workqueue.c:2542) 
[ 2285.986264][ T11] ? assign_work (kernel/workqueue.c:1101) 
[ 2285.986507][ T11] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[ 2285.986760][ T11] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[ 2285.987077][ T11] kthread (kernel/kthread.c:388) 
[ 2285.987296][ T11] ? __pfx_kthread (kernel/kthread.c:341) 
[ 2285.987543][ T11] ret_from_fork (arch/x86/kernel/process.c:153) 
[ 2285.987777][ T11] ? __pfx_kthread (kernel/kthread.c:341) 
[ 2285.988074][ T11] ret_from_fork_asm (arch/x86/entry/entry_64.S:250) 
| [ 2285.991310][   T11] ------------[ cut here ]------------
| [ 2285.991652][   T11] sysfs group 'bridge' not found for kobject 'test-br0'
| [ 2285.992121][ T11] WARNING: CPU: 0 PID: 11 at fs/sysfs/group.c:282 sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
| [ 2285.992610][   T11] Modules linked in: xfrm_user psample macsec fou ip6_gre ip_gre gre cls_u32 sch_htb xt_mark sch_ingress act_mirred cls_basic sch_fq_codel nft_compat nf_tables libcrc32c vxlan ip6_udp_tunnel udp_tunnel mpls_iptunnel mpls_router [last unloaded: netdevsim]
[ 2285.994474][   T11] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 2285.995183][   T11] Workqueue: netns cleanup_net
[ 2285.995475][ T11] RIP: 0010:sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 2285.995807][ T11] Code: 89 d9 49 8b 14 24 48 b8 00 00 00 00 00 fc ff df 48 c1 e9 03 80 3c 01 00 75 45 48 8b 33 48 c7 c7 a0 a7 5c b7 e8 60 65 5e ff 90 <0f> 0b 90 90 48 83 c4 08 5b 5d 41 5c c3 cc cc cc cc e8 e9 c7 da ff
All code
========
   0:	89 d9                	mov    %ebx,%ecx
   2:	49 8b 14 24          	mov    (%r12),%rdx
   6:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
   d:	fc ff df 
  10:	48 c1 e9 03          	shr    $0x3,%rcx
  14:	80 3c 01 00          	cmpb   $0x0,(%rcx,%rax,1)
  18:	75 45                	jne    0x5f
  1a:	48 8b 33             	mov    (%rbx),%rsi
  1d:	48 c7 c7 a0 a7 5c b7 	mov    $0xffffffffb75ca7a0,%rdi
  24:	e8 60 65 5e ff       	call   0xffffffffff5e6589
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	48 83 c4 08          	add    $0x8,%rsp
  32:	5b                   	pop    %rbx
  33:	5d                   	pop    %rbp
  34:	41 5c                	pop    %r12
  36:	c3                   	ret
  37:	cc                   	int3
  38:	cc                   	int3
  39:	cc                   	int3
  3a:	cc                   	int3
  3b:	e8 e9 c7 da ff       	call   0xffffffffffdac829

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	48 83 c4 08          	add    $0x8,%rsp
   8:	5b                   	pop    %rbx
   9:	5d                   	pop    %rbp
   a:	41 5c                	pop    %r12
   c:	c3                   	ret
   d:	cc                   	int3
   e:	cc                   	int3
   f:	cc                   	int3
  10:	cc                   	int3
  11:	e8 e9 c7 da ff       	call   0xffffffffffdac7ff
[ 2285.996860][   T11] RSP: 0018:ffffc900000bfba0 EFLAGS: 00010282
[ 2285.997244][   T11] RAX: 0000000000000000 RBX: ffffffffb79be220 RCX: ffffffffb491056f
[ 2285.997695][   T11] RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000001
[ 2285.998143][   T11] RBP: 0000000000000000 R08: 0000000000000000 R09: fffff52000017f19
[ 2285.998557][   T11] R10: ffffc900000bf8cf R11: 205d313154202020 R12: ffff8880059fa628
[ 2285.998976][   T11] R13: ffff8880059fadf8 R14: ffffc900000bfc98 R15: ffff8880059fabc0
[ 2285.999392][   T11] FS:  0000000000000000(0000) GS:ffff888035200000(0000) knlGS:0000000000000000
[ 2285.999860][   T11] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2286.000212][   T11] CR2: 0000561aaba2ddec CR3: 0000000016764006 CR4: 00000000001706f0
[ 2286.000691][   T11] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 2286.001169][   T11] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 2286.001622][   T11] Call Trace:
[ 2286.001806][   T11]  <TASK>
[ 2286.002010][ T11] ? __warn (kernel/panic.c:677) 
[ 2286.002247][ T11] ? console_trylock (kernel/printk/printk.c:2659 kernel/printk/printk.c:2654) 
[ 2286.002503][ T11] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 2286.002811][ T11] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[ 2286.003100][ T11] ? handle_bug (arch/x86/kernel/traps.c:238) 
[ 2286.003357][ T11] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[ 2286.003628][ T11] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[ 2286.003940][ T11] ? desc_read (./arch/x86/include/asm/atomic64_64.h:20 ./include/linux/atomic/atomic-arch-fallback.h:2615 ./include/linux/atomic/atomic-long.h:79 ./include/linux/atomic/atomic-instrumented.h:3196 kernel/printk/printk_ringbuffer.c:534) 
[ 2286.004216][ T11] ? sysfs_remove_group (fs/sysfs/group.c:282 (discriminator 1)) 
[ 2286.004528][ T11] br_dev_delete (net/bridge/br_if.c:396) 
[ 2286.004791][ T11] br_net_exit_batch_rtnl (net/bridge/br.c:369) 
[ 2286.005109][ T11] cleanup_net (net/core/net_namespace.c:628 (discriminator 2)) 
[ 2286.005382][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 2286.005713][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:581) 
[ 2286.006002][ T11] ? lock_acquire (./include/trace/events/lock.h:24 kernel/locking/lockdep.c:5725) 
[ 2286.006285][ T11] ? process_one_work (kernel/workqueue.c:2609) 
[ 2286.006599][ T11] process_one_work (kernel/workqueue.c:2638) 
[ 2286.006897][ T11] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:228) 
[ 2286.007164][ T11] ? __pfx_process_one_work (kernel/workqueue.c:2542) 
[ 2286.007451][ T11] ? assign_work (kernel/workqueue.c:1101) 
[ 2286.007696][ T11] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[ 2286.007954][ T11] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[ 2286.008228][ T11] kthread (kernel/kthread.c:388) 
[ 2286.008443][ T11] ? __pfx_kthread (kernel/kthread.c:341) 
[ 2286.008689][ T11] ret_from_fork (arch/x86/kernel/process.c:153) 
[ 2286.008932][ T11] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
dump_stack_lvl:print_report:kasan_report:kobject_put
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