======================================
| [   63.340448][   T69] ==================================================================
| [   63.340854][   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)
| [   63.341143][   T69] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/69
| [   63.341413][   T69]
[   63.341519][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   63.341522][   T69] Workqueue: netns cleanup_net
[   63.341543][   T69] Call Trace:
[   63.341545][   T69]  <TASK>
[   63.341548][   T69]  dump_stack_lvl (lib/dump_stack.c:123)
[   63.341559][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   63.341562][   T69]  kasan_report (mm/kasan/report.c:597)
[   63.341571][   T69]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   63.341577][   T69]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   63.341581][   T69]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   63.341586][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   63.341589][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   63.341593][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2590)
[   63.341597][   T69]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   63.341612][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   63.341617][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   63.341622][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   63.341626][   T69]  ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:119 kernel/softirq.c:455)
[   63.341633][   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)
[   63.341637][   T69]  ? netif_set_allmulti (net/core/dev.c:9890)
[   63.341642][   T69]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   63.341649][   T69]  netif_change_flags (net/core/dev.c:9989)
[   63.341656][   T69]  dev_change_flags (./include/net/netdev_lock.h:30 ./include/net/netdev_lock.h:47 net/core/dev_api.c:69)
[   63.341662][   T69]  cycle_netdev (drivers/net/vrf.c:1052)
[   63.341673][   T69]  vrf_dellink (drivers/net/vrf.c:1671)
[   63.341676][   T69]  ? vrf_map_unregister_dev (drivers/net/vrf.c:1667)
[   63.341682][   T69]  default_device_exit_batch (net/core/dev.c:13221 (discriminator 2))
[   63.341686][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   63.341692][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   63.341698][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   63.341701][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   63.341707][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   63.341712][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   63.341716][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   63.341724][   T69]  process_one_work (kernel/workqueue.c:3268)
[   63.341730][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   63.341737][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   63.341741][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   63.341748][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   63.341751][   T69]  kthread (kernel/kthread.c:463)
[   63.341757][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   63.341760][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   63.341767][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   63.341771][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   63.341775][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   63.341779][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   63.341781][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   63.341784][   T69]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   63.351377][   T69] #PF: error_code(0x0002) - not-present page
| [   63.351590][   T69] PGD 0 P4D 0
| [   63.351731][   T69] Oops: Oops: 0002 [#1] SMP KASAN
| [   63.352297][   T69] Tainted: [B]=BAD_PAGE
[   63.352429][   T69] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   63.352644][   T69] Workqueue: netns cleanup_net
[   63.352833][   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)
[   63.353060][   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
[   63.353674][   T69] RSP: 0018:ffffc900004a7698 EFLAGS: 00010046
[   63.353890][   T69] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffffade49b8a
[   63.354142][   T69] RDX: fffffbfff656cacd RSI: 0000000000000008 RDI: ffffffffb2b65660
[   63.354399][   T69] RBP: ffffc900004a7700 R08: 0000000000000001 R09: fffffbfff656cacc
[   63.354685][   T69] R10: ffffffffb2b65667 R11: ffffc900004a7180 R12: 0000000000000000
[   63.354954][   T69] R13: 0000000000000282 R14: ffff8880053d1000 R15: dffffc0000000000
[   63.355211][   T69] FS:  0000000000000000(0000) GS:ffff8880b4187000(0000) knlGS:0000000000000000
[   63.355512][   T69] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   63.355736][   T69] CR2: 0000000000000000 CR3: 000000006db49005 CR4: 0000000000772ef0
[   63.355999][   T69] PKRU: 55555554
[   63.356127][   T69] Call Trace:
[   63.356264][   T69]  <TASK>
[   63.356360][   T69]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   63.356542][   T69]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   63.356741][   T69]  ? queue_delayed_work_on (kernel/workqueue.c:2590)
[   63.356911][   T69]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4472)
[   63.357082][   T69]  __cancel_work_sync (kernel/workqueue.c:4383)
[   63.357257][   T69]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   63.357453][   T69]  ? netdev_notify_peers (net/core/dev.c:1891)
[   63.357628][   T69]  ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:119 kernel/softirq.c:455)
[   63.357803][   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)
[   63.357973][   T69]  ? netif_set_allmulti (net/core/dev.c:9890)
[   63.358169][   T69]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   63.358345][   T69]  netif_change_flags (net/core/dev.c:9989)
[   63.358518][   T69]  dev_change_flags (./include/net/netdev_lock.h:30 ./include/net/netdev_lock.h:47 net/core/dev_api.c:69)
[   63.358707][   T69]  cycle_netdev (drivers/net/vrf.c:1052)
[   63.358838][   T69]  vrf_dellink (drivers/net/vrf.c:1671)
[   63.358966][   T69]  ? vrf_map_unregister_dev (drivers/net/vrf.c:1667)
[   63.359137][   T69]  default_device_exit_batch (net/core/dev.c:13221 (discriminator 2))
[   63.359310][   T69]  ? unregister_netdev (net/core/dev.c:13204)
[   63.359483][   T69]  ops_undo_list (net/core/net_namespace.c:251)
[   63.359671][   T69]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   63.359843][   T69]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   63.360024][   T69]  cleanup_net (net/core/net_namespace.c:698)
[   63.360196][   T69]  ? net_passive_dec (net/core/net_namespace.c:660)
[   63.360379][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   63.360558][   T69]  process_one_work (kernel/workqueue.c:3268)
[   63.360740][   T69]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   63.360910][   T69]  ? assign_work (kernel/workqueue.c:1206)
[   63.361078][   T69]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   63.361255][   T69]  ? rescuer_thread (kernel/workqueue.c:3373)
[   63.361434][   T69]  kthread (kernel/kthread.c:463)
[   63.361563][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   63.361740][   T69]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   63.361910][   T69]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   63.362085][   T69]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   63.362260][   T69]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   63.362441][   T69]  ret_from_fork (arch/x86/kernel/process.c:164)
[   63.362611][   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