======================================
| xx__-> [   19.367312][   T69] ==================================================================
| [   19.367749][   T69] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   19.368041][   T69] Read of size 1 at addr ffff888008b8c6c4 by task kworker/u16:1/69
| [   19.368292][   T69]
[   19.368404][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.368409][   T69] Workqueue: netns cleanup_net
[   19.368421][   T69] Call Trace:
[   19.368425][   T69]  <TASK>
[   19.368428][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   19.368434][   T69]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   19.368447][   T69]  ? kobject_put (lib/kobject.c:733)
[   19.368451][   T69]  print_report (mm/kasan/report.c:483)
[   19.368455][   T69]  ? kobject_put (lib/kobject.c:733)
[   19.368458][   T69]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   19.368462][   T69]  ? kobject_put (lib/kobject.c:733)
[   19.368465][   T69]  kasan_report (mm/kasan/report.c:597)
[   19.368469][   T69]  ? kobject_put (lib/kobject.c:733)
[   19.368474][   T69]  kobject_put (lib/kobject.c:733)
[   19.368478][   T69]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   19.368484][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   19.368488][   T69]  ? generic_xdp_install (net/core/dev.c:11630)
[   19.368491][   T69]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   19.368502][   T69]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   19.368507][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.368511][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.368517][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   19.368521][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.368526][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.368539][   T69]  process_one_work (kernel/workqueue.c:3268)
[   19.368550][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.368556][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   19.368560][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.368566][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.368570][   T69]  kthread (kernel/kthread.c:463)
[   19.368574][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.368576][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.368584][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.368589][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.368593][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.368596][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.368599][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.368602][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   19.388121][   T69] refcount_t: underflow; use-after-free.
| [   19.388321][   T69] WARNING: CPU: 1 PID: 69 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   19.388602][   T69] Modules linked in: nft_compat nf_tables
| [   19.389530][   T69] Tainted: [B]=BAD_PAGE
[   19.389657][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.389849][   T69] Workqueue: netns cleanup_net
[   19.390015][   T69] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   19.390211][   T69] 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 ba 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 ba 	mov    $0xffffffffbaa5ba40,%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
[   19.390825][   T69] RSP: 0018:ffffc900004a7a08 EFLAGS: 00010282
[   19.391021][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   19.391247][   T69] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   19.391477][   T69] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff7740934
[   19.391788][   T69] R10: 0000000000000003 R11: ffffc900004a7580 R12: 0000000000000001
[   19.392010][   T69] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   19.392235][   T69] FS:  0000000000000000(0000) GS:ffff8880a9b88000(0000) knlGS:0000000000000000
[   19.392511][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   19.392767][   T69] CR2: 00007f21edd2e000 CR3: 0000000070349002 CR4: 0000000000772ef0
[   19.392991][   T69] PKRU: 55555554
[   19.393111][   T69] Call Trace:
[   19.393232][   T69]  <TASK>
[   19.393314][   T69]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   19.393482][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   19.393697][   T69]  ? generic_xdp_install (net/core/dev.c:11630)
[   19.393850][   T69]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   19.394006][   T69]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   19.394157][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.394304][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.394478][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   19.394685][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.394837][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.394992][   T69]  process_one_work (kernel/workqueue.c:3268)
[   19.395149][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.395299][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   19.395459][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.395611][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.395768][   T69]  kthread (kernel/kthread.c:463)
[   19.395885][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.396032][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.396186][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.396341][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.396500][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.396658][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.396806][   T69]  ? 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