======================================
| xx__-> [   15.522132][   T71] ==================================================================
| [   15.522440][   T71] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   15.522702][   T71] Read of size 1 at addr ffff888007d696c4 by task kworker/u16:1/71
| [   15.522959][   T71]
[   15.523056][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   15.523058][   T71] Workqueue: netns cleanup_net
[   15.523071][   T71] Call Trace:
[   15.523073][   T71]  <TASK>
[   15.523075][   T71]  dump_stack_lvl (lib/dump_stack.c:123)
[   15.523080][   T71]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   15.523089][   T71]  ? kobject_put (lib/kobject.c:733)
[   15.523093][   T71]  print_report (mm/kasan/report.c:483)
[   15.523097][   T71]  ? kobject_put (lib/kobject.c:733)
[   15.523102][   T71]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   15.523106][   T71]  ? kobject_put (lib/kobject.c:733)
[   15.523108][   T71]  kasan_report (mm/kasan/report.c:597)
[   15.523112][   T71]  ? kobject_put (lib/kobject.c:733)
[   15.523118][   T71]  kobject_put (lib/kobject.c:733)
[   15.523121][   T71]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   15.523126][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   15.523130][   T71]  ? generic_xdp_install (net/core/dev.c:11630)
[   15.523132][   T71]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   15.523143][   T71]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   15.523148][   T71]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   15.523151][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   15.523157][   T71]  cleanup_net (net/core/net_namespace.c:698)
[   15.523161][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[   15.523166][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.523173][   T71]  process_one_work (kernel/workqueue.c:3268)
[   15.523184][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   15.523189][   T71]  ? assign_work (kernel/workqueue.c:1206)
[   15.523194][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   15.523199][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[   15.523203][   T71]  kthread (kernel/kthread.c:463)
[   15.523207][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.523210][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   15.523216][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   15.523220][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.523223][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.523227][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[   15.523230][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.523233][   T71]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   15.543724][   T71] refcount_t: underflow; use-after-free.
| [   15.543937][   T71] WARNING: CPU: 2 PID: 71 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   15.544250][   T71] Modules linked in:
| [   15.544812][   T71] Tainted: [B]=BAD_PAGE
[   15.544961][   T71] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   15.545184][   T71] Workqueue: netns cleanup_net
[   15.545379][   T71] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   15.545639][   T71] Code: cc 38 03 80 fb 01 0f 87 29 33 d7 fe 83 e3 01 0f 85 51 ff ff ff c6 05 17 cc 38 03 01 90 48 c7 c7 40 ba a5 88 e8 62 d6 16 ff 90 <0f> 0b 90 90 e9 33 ff ff ff 48 89 df e8 c0 9d a0 ff e9 ba fe ff ff
All code
========
   0:	cc                   	int3
   1:	38 03                	cmp    %al,(%rbx)
   3:	80 fb 01             	cmp    $0x1,%bl
   6:	0f 87 29 33 d7 fe    	ja     0xfffffffffed73335
   c:	83 e3 01             	and    $0x1,%ebx
   f:	0f 85 51 ff ff ff    	jne    0xffffffffffffff66
  15:	c6 05 17 cc 38 03 01 	movb   $0x1,0x338cc17(%rip)        # 0x338cc33
  1c:	90                   	nop
  1d:	48 c7 c7 40 ba a5 88 	mov    $0xffffffff88a5ba40,%rdi
  24:	e8 62 d6 16 ff       	call   0xffffffffff16d68b
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	e9 33 ff ff ff       	jmp    0xffffffffffffff66
  33:	48 89 df             	mov    %rbx,%rdi
  36:	e8 c0 9d a0 ff       	call   0xffffffffffa09dfb
  3b:	e9 ba fe ff ff       	jmp    0xfffffffffffffefa

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	e9 33 ff ff ff       	jmp    0xffffffffffffff3c
   9:	48 89 df             	mov    %rbx,%rdi
   c:	e8 c0 9d a0 ff       	call   0xffffffffffa09dd1
  11:	e9 ba fe ff ff       	jmp    0xfffffffffffffed0
[   15.546235][   T71] RSP: 0018:ffffc900004c7a08 EFLAGS: 00010282
[   15.546483][   T71] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   15.546754][   T71] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   15.547017][   T71] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff1340934
[   15.547287][   T71] R10: 0000000000000003 R11: ffffc900004c7580 R12: 0000000000000001
[   15.547571][   T71] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   15.547842][   T71] FS:  0000000000000000(0000) GS:ffff8880e2208000(0000) knlGS:0000000000000000
[   15.548150][   T71] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   15.548383][   T71] CR2: 00007f4ccbaf1920 CR3: 000000000b302004 CR4: 0000000000772ef0
[   15.548667][   T71] PKRU: 55555554
[   15.548823][   T71] Call Trace:
[   15.548969][   T71]  <TASK>
[   15.549081][   T71]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   15.549271][   T71]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   15.549479][   T71]  ? generic_xdp_install (net/core/dev.c:11630)
[   15.549663][   T71]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   15.549849][   T71]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   15.550036][   T71]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   15.550222][   T71]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   15.550418][   T71]  cleanup_net (net/core/net_namespace.c:698)
[   15.550615][   T71]  ? net_passive_dec (net/core/net_namespace.c:660)
[   15.550803][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.550989][   T71]  process_one_work (kernel/workqueue.c:3268)
[   15.551177][   T71]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   15.551364][   T71]  ? assign_work (kernel/workqueue.c:1206)
[   15.551569][   T71]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   15.551759][   T71]  ? rescuer_thread (kernel/workqueue.c:3373)
[   15.551948][   T71]  kthread (kernel/kthread.c:463)
[   15.552096][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.552283][   T71]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   15.552486][   T71]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   15.552672][   T71]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   15.552869][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   15.553055][   T71]  ret_from_fork (arch/x86/kernel/process.c:164)
[   15.553243][   T71]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
print_report:kasan_report:kobject_put:netdev_run_todo:ops_undo_list
refcount_warn_saturate:netdev_run_todo:ops_undo_list:cleanup_net:process_one_work