======================================
| xx__-> [   18.916188][   T69] ==================================================================
| [   18.916500][   T69] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   18.916766][   T69] Read of size 1 at addr ffff8880082796c4 by task kworker/u16:1/69
| [   18.917028][   T69]
[   18.917127][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   18.917130][   T69] Workqueue: netns cleanup_net
[   18.917141][   T69] Call Trace:
[   18.917143][   T69]  <TASK>
[   18.917146][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   18.917153][   T69]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   18.917165][   T69]  ? kobject_put (lib/kobject.c:733)
[   18.917170][   T69]  print_report (mm/kasan/report.c:483)
[   18.917175][   T69]  ? kobject_put (lib/kobject.c:733)
[   18.917179][   T69]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   18.917183][   T69]  ? kobject_put (lib/kobject.c:733)
[   18.917186][   T69]  kasan_report (mm/kasan/report.c:597)
[   18.917190][   T69]  ? kobject_put (lib/kobject.c:733)
[   18.917195][   T69]  kobject_put (lib/kobject.c:733)
[   18.917199][   T69]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   18.917207][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   18.917211][   T69]  ? generic_xdp_install (net/core/dev.c:11630)
[   18.917214][   T69]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   18.917224][   T69]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   18.917230][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   18.917233][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   18.917239][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   18.917243][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   18.917248][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.917256][   T69]  process_one_work (kernel/workqueue.c:3268)
[   18.917267][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   18.917273][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   18.917277][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   18.917283][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   18.917287][   T69]  kthread (kernel/kthread.c:463)
[   18.917291][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.917293][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   18.917299][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   18.917304][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.917308][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.917311][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   18.917314][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.917317][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   18.936535][   T69] refcount_t: underflow; use-after-free.
| [   18.936862][   T69] WARNING: CPU: 1 PID: 69 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   18.937238][   T69] Modules linked in: sch_fq
| [   18.937916][   T69] Tainted: [B]=BAD_PAGE
[   18.938058][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   18.938295][   T69] Workqueue: netns cleanup_net
[   18.938477][   T69] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   18.938718][   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 85 aa 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 85 aa 	mov    $0xffffffffaa85ba40,%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
[   18.939353][   T69] RSP: 0018:ffffc900004a7a08 EFLAGS: 00010282
[   18.939569][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   18.939862][   T69] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   18.940159][   T69] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff5700934
[   18.940442][   T69] R10: 0000000000000003 R11: ffffc900004a7580 R12: 0000000000000001
[   18.940729][   T69] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   18.941034][   T69] FS:  0000000000000000(0000) GS:ffff8880c0388000(0000) knlGS:0000000000000000
[   18.941357][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   18.941601][   T69] CR2: 00005611f8340880 CR3: 0000000004c87003 CR4: 0000000000772ef0
[   18.941908][   T69] PKRU: 55555554
[   18.942054][   T69] Call Trace:
[   18.942195][   T69]  <TASK>
[   18.942293][   T69]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   18.942492][   T69]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   18.942679][   T69]  ? generic_xdp_install (net/core/dev.c:11630)
[   18.942876][   T69]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   18.943094][   T69]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   18.943283][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   18.943466][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   18.943652][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   18.943859][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   18.944064][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.944255][   T69]  process_one_work (kernel/workqueue.c:3268)
[   18.944444][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   18.944633][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   18.944825][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   18.945037][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   18.945223][   T69]  kthread (kernel/kthread.c:463)
[   18.945349][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.945512][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   18.945780][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   18.945976][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   18.946152][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   18.946330][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   18.946583][   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