======================================
| [   62.813061][   T69] ==================================================================
| [   62.813505][   T69] BUG: KASAN: null-ptr-deref in try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
| [   62.813912][   T69] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/69
| [   62.814287][   T69]
[   62.814443][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   62.814446][   T69] Workqueue: netns cleanup_net
[   62.814461][   T69] Call Trace:
[   62.814463][   T69]  <TASK>
[   62.814467][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   62.814480][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   62.814485][   T69]  kasan_report (mm/kasan/report.c:597)
[   62.814493][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   62.814502][   T69]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   62.814508][   T69]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   62.814515][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   62.814520][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   62.814526][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2590)
[   62.814531][   T69]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   62.814544][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   62.814550][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   62.814557][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   62.814563][   T69]  ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:119 kernel/softirq.c:455)
[   62.814571][   T69]  __dev_change_flags (./include/linux/list.h:119 ./include/linux/list.h:223 ./include/linux/list.h:237 net/core/dev.c:1945 net/core/dev.c:9924)
[   62.814577][   T69]  ? netif_set_allmulti (net/core/dev.c:9890)
[   62.814584][   T69]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   62.814592][   T69]  netif_change_flags (net/core/dev.c:9989)
[   62.814599][   T69]  dev_change_flags (./include/net/netdev_lock.h:30 ./include/net/netdev_lock.h:47 net/core/dev_api.c:69)
[   62.814606][   T69]  cycle_netdev (drivers/net/vrf.c:1052)
[   62.814613][   T69]  vrf_dellink (drivers/net/vrf.c:1671)
[   62.814618][   T69]  ? vrf_map_unregister_dev (drivers/net/vrf.c:1667)
[   62.814627][   T69]  default_device_exit_batch (net/core/dev.c:13221 (discriminator 2))
[   62.814633][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   62.814643][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   62.814651][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   62.814656][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   62.814665][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   62.814672][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   62.814679][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   62.814687][   T69]  process_one_work (kernel/workqueue.c:3268)
[   62.814698][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   62.814707][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   62.814714][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   62.814724][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   62.814729][   T69]  kthread (kernel/kthread.c:463)
[   62.814736][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   62.814740][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   62.814744][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   62.814750][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   62.814754][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   62.814760][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   62.814763][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   62.814768][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   62.828402][   T69] #PF: error_code(0x0002) - not-present page
| [   62.828702][   T69] PGD 0 P4D 0
| [   62.828894][   T69] Oops: Oops: 0002 [#1] SMP KASAN
| [   62.829704][   T69] Tainted: [B]=BAD_PAGE
[   62.829893][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   62.830199][   T69] Workqueue: netns cleanup_net
[   62.830464][   T69] RIP: 0010:try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   62.830784][   T69] Code: 00 41 89 c0 b8 01 00 00 00 45 85 c0 74 0f 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 be 08 00 00 00 48 89 df e8 1f 93 82 00 <f0> 48 0f ba 2b 00 72 11 48 83 c4 10 31 c0 5b 5d 41 5c 41 5d 41 5e
All code
========
   0:	00 41 89             	add    %al,-0x77(%rcx)
   3:	c0 b8 01 00 00 00 45 	sarb   $0x45,0x1(%rax)
   a:	85 c0                	test   %eax,%eax
   c:	74 0f                	je     0x1d
   e:	48 83 c4 10          	add    $0x10,%rsp
  12:	5b                   	pop    %rbx
  13:	5d                   	pop    %rbp
  14:	41 5c                	pop    %r12
  16:	41 5d                	pop    %r13
  18:	41 5e                	pop    %r14
  1a:	41 5f                	pop    %r15
  1c:	c3                   	ret
  1d:	be 08 00 00 00       	mov    $0x8,%esi
  22:	48 89 df             	mov    %rbx,%rdi
  25:	e8 1f 93 82 00       	call   0x829349
  2a:*	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)		<-- trapping instruction
  30:	72 11                	jb     0x43
  32:	48 83 c4 10          	add    $0x10,%rsp
  36:	31 c0                	xor    %eax,%eax
  38:	5b                   	pop    %rbx
  39:	5d                   	pop    %rbp
  3a:	41 5c                	pop    %r12
  3c:	41 5d                	pop    %r13
  3e:	41 5e                	pop    %r14

Code starting with the faulting instruction
===========================================
   0:	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)
   6:	72 11                	jb     0x19
   8:	48 83 c4 10          	add    $0x10,%rsp
   c:	31 c0                	xor    %eax,%eax
   e:	5b                   	pop    %rbx
   f:	5d                   	pop    %rbp
  10:	41 5c                	pop    %r12
  12:	41 5d                	pop    %r13
  14:	41 5e                	pop    %r14
[   62.831663][   T69] RSP: 0018:ffffc900004a7698 EFLAGS: 00010046
[   62.831976][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff88c49b8a
[   62.832348][   T69] RDX: fffffbfff1b2cacd RSI: 0000000000000008 RDI: ffffffff8d965660
[   62.832722][   T69] RBP: ffffc900004a7700 R08: 0000000000000001 R09: fffffbfff1b2cacc
[   62.833084][   T69] R10: ffffffff8d965667 R11: ffffc900004a7180 R12: 0000000000000000
[   62.833455][   T69] R13: 0000000000000282 R14: ffff888005344000 R15: dffffc0000000000
[   62.833825][   T69] FS:  0000000000000000(0000) GS:ffff8880d9387000(0000) knlGS:0000000000000000
[   62.834275][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   62.834590][   T69] CR2: 0000000000000000 CR3: 000000000f939001 CR4: 0000000000772ef0
[   62.834955][   T69] PKRU: 55555554
[   62.835136][   T69] Call Trace:
[   62.835319][   T69]  <TASK>
[   62.835452][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   62.835694][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   62.835945][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2590)
[   62.836190][   T69]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   62.836441][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   62.836682][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   62.836924][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   62.837166][   T69]  ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:119 kernel/softirq.c:455)
[   62.837411][   T69]  __dev_change_flags (./include/linux/list.h:119 ./include/linux/list.h:223 ./include/linux/list.h:237 net/core/dev.c:1945 net/core/dev.c:9924)
[   62.837662][   T69]  ? netif_set_allmulti (net/core/dev.c:9890)
[   62.837903][   T69]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   62.838146][   T69]  netif_change_flags (net/core/dev.c:9989)
[   62.838392][   T69]  dev_change_flags (./include/net/netdev_lock.h:30 ./include/net/netdev_lock.h:47 net/core/dev_api.c:69)
[   62.838636][   T69]  cycle_netdev (drivers/net/vrf.c:1052)
[   62.838819][   T69]  vrf_dellink (drivers/net/vrf.c:1671)
[   62.838999][   T69]  ? vrf_map_unregister_dev (drivers/net/vrf.c:1667)
[   62.839247][   T69]  default_device_exit_batch (net/core/dev.c:13221 (discriminator 2))
[   62.839495][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   62.839742][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   62.839985][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   62.840228][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   62.840473][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   62.840742][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   62.840999][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   62.841248][   T69]  process_one_work (kernel/workqueue.c:3268)
[   62.841492][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   62.841736][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   62.841976][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   62.842224][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   62.842463][   T69]  kthread (kernel/kthread.c:463)
[   62.842647][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   62.842890][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   62.843137][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   62.843382][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   62.843623][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   62.844031][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   62.844277][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)


Finger prints:
try_to_grab_pending:__cancel_work:__cancel_work_sync:__dev_close_many:__dev_change_flags
kasan_report:kasan_check_range:try_to_grab_pending:__cancel_work:__cancel_work_sync