======================================
| xx__-> [   19.502864][   T12] ==================================================================
| [   19.503181][   T12] BUG: KASAN: slab-use-after-free in kobject_put (lib/kobject.c:733)
| [   19.503438][   T12] Read of size 1 at addr ffff8880050a46c4 by task kworker/u16:0/12
| [   19.503689][   T12]
[   19.503781][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.503784][   T12] Workqueue: netns cleanup_net
[   19.503794][   T12] Call Trace:
[   19.503796][   T12]  <TASK>
[   19.503800][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[   19.503806][   T12]  print_address_description.constprop.0 (mm/kasan/report.c:379)
[   19.503815][   T12]  ? kobject_put (lib/kobject.c:733)
[   19.503819][   T12]  print_report (mm/kasan/report.c:483)
[   19.503822][   T12]  ? kobject_put (lib/kobject.c:733)
[   19.503825][   T12]  ? kasan_addr_to_slab (./include/linux/mm.h:1245 mm/kasan/../slab.h:191 mm/kasan/common.c:47)
[   19.503829][   T12]  ? kobject_put (lib/kobject.c:733)
[   19.503832][   T12]  kasan_report (mm/kasan/report.c:597)
[   19.503836][   T12]  ? kobject_put (lib/kobject.c:733)
[   19.503841][   T12]  kobject_put (lib/kobject.c:733)
[   19.503845][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   19.503852][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   19.503855][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[   19.503858][   T12]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   19.503873][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   19.503878][   T12]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.503882][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.503888][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   19.503892][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.503897][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.503905][   T12]  process_one_work (kernel/workqueue.c:3268)
[   19.503915][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.503921][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   19.503926][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.503931][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.503935][   T12]  kthread (kernel/kthread.c:463)
[   19.503940][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.503942][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.503948][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.503953][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.503956][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.503960][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.503962][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.503966][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   19.524129][   T12] refcount_t: underflow; use-after-free.
| [   19.524322][   T12] WARNING: CPU: 1 PID: 12 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
| [   19.524640][   T12] Modules linked in:
| [   19.525288][   T12] Tainted: [B]=BAD_PAGE
[   19.525431][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.525643][   T12] Workqueue: netns cleanup_net
[   19.525819][   T12] RIP: 0010:refcount_warn_saturate (lib/refcount.c:28 (discriminator 3))
[   19.526161][   T12] 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 e5 8b 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 e5 8b 	mov    $0xffffffff8be5ba40,%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
[   19.526771][   T12] RSP: 0018:ffffc900000c7a08 EFLAGS: 00010282
[   19.527090][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[   19.527333][   T12] RDX: 0000000000000002 RSI: 0000000000000004 RDI: 0000000000000001
[   19.527588][   T12] RBP: 0000000000000003 R08: 0000000000000000 R09: fffffbfff19c0934
[   19.527959][   T12] R10: 0000000000000003 R11: ffffc900000c7580 R12: 0000000000000001
[   19.528232][   T12] R13: dffffc0000000000 R14: dead000000000122 R15: dead000000000100
[   19.528582][   T12] FS:  0000000000000000(0000) GS:ffff8880ded88000(0000) knlGS:0000000000000000
[   19.528877][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   19.529117][   T12] CR2: 00007ffdf5220fd8 CR3: 0000000017149003 CR4: 0000000000772ef0
[   19.529463][   T12] PKRU: 55555554
[   19.529591][   T12] Call Trace:
[   19.529714][   T12]  <TASK>
[   19.529807][   T12]  netdev_run_todo (./include/linux/list.h:381 net/core/dev.c:11670)
[   19.530092][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12299)
[   19.530256][   T12]  ? generic_xdp_install (net/core/dev.c:11630)
[   19.530422][   T12]  ? net_generic (./include/linux/rcupdate.h:341 ./include/linux/rcupdate.h:897 ./include/net/netns/generic.h:48)
[   19.530598][   T12]  ops_undo_list (net/core/net_namespace.c:190 net/core/net_namespace.c:248)
[   19.530776][   T12]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.531058][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.531251][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   19.531430][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.531638][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.531945][   T12]  process_one_work (kernel/workqueue.c:3268)
[   19.532118][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.532285][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   19.532466][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.532722][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.532884][   T12]  kthread (kernel/kthread.c:463)
[   19.533035][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.533210][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.533476][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.533648][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.533811][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.533994][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.534264][   T12]  ? 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