======================================
| [   19.593527][   T70] ==================================================================
| [   19.593929][   T70] 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)
| [   19.594341][   T70] Write of size 8 at addr 0000000000000000 by task kworker/u16:1/70
| [   19.594742][   T70]
[   19.594899][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.594903][   T70] Workqueue: netns cleanup_net
[   19.594916][   T70] Call Trace:
[   19.594922][   T70]  <TASK>
[   19.594926][   T70]  dump_stack_lvl (lib/dump_stack.c:123)
[   19.594935][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.594940][   T70]  kasan_report (mm/kasan/report.c:597)
[   19.594950][   T70]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.594959][   T70]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   19.594966][   T70]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   19.594970][   T70]  ? irqentry_exit (kernel/entry/common.c:215)
[   19.594977][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.594980][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.594986][   T70]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   19.594990][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.594994][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.594999][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.595002][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   19.595006][   T70]  netif_close_many (net/core/dev.c:1959)
[   19.595009][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   19.595014][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   19.595017][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.595020][   T70]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   19.595024][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.595028][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[   19.595033][   T70]  ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3189 kernel/locking/mutex.h:47 kernel/locking/mutex.c:67)
[   19.595036][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.595039][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.595042][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.595045][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.595048][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.595054][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   19.595058][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   19.595064][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   19.595069][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.595072][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.595078][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   19.595082][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.595087][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.595093][   T70]  process_one_work (kernel/workqueue.c:3268)
[   19.595100][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.595105][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   19.595110][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.595115][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.595119][   T70]  kthread (kernel/kthread.c:463)
[   19.595124][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.595127][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.595131][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.595134][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.595137][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.595141][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.595143][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.595146][   T70]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   19.611128][   T70] #PF: error_code(0x0002) - not-present page
| [   19.611452][   T70] PGD 0 P4D 0
| [   19.611654][   T70] Oops: Oops: 0002 [#1] SMP KASAN
| [   19.612541][   T70] Tainted: [B]=BAD_PAGE
[   19.612746][   T70] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   19.613074][   T70] Workqueue: netns cleanup_net
[   19.613354][   T70] 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)
[   19.613696][   T70] 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
[   19.614621][   T70] RSP: 0018:ffffc900004b7680 EFLAGS: 00010046
[   19.614955][   T70] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8a049b8a
[   19.615353][   T70] RDX: fffffbfff1dacacd RSI: 0000000000000008 RDI: ffffffff8ed65660
[   19.615746][   T70] RBP: ffffc900004b76e8 R08: 0000000000000001 R09: fffffbfff1dacacc
[   19.616131][   T70] R10: ffffffff8ed65667 R11: ffffc900004b7140 R12: 0000000000000000
[   19.616516][   T70] R13: 0000000000000282 R14: ffff88800c5a1000 R15: dffffc0000000000
[   19.616908][   T70] FS:  0000000000000000(0000) GS:ffff8880de387000(0000) knlGS:0000000000000000
[   19.617366][   T70] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   19.617695][   T70] CR2: 0000000000000000 CR3: 0000000015749006 CR4: 0000000000772ef0
[   19.618089][   T70] PKRU: 55555554
[   19.618328][   T70] Call Trace:
[   19.618522][   T70]  <TASK>
[   19.618676][   T70]  ? irqentry_exit (kernel/entry/common.c:215)
[   19.618955][   T70]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   19.619224][   T70]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   19.619489][   T70]  ? queue_delayed_work_on (kernel/workqueue.c:2567)
[   19.619752][   T70]  __cancel_work_sync (kernel/workqueue.c:4383)
[   19.620013][   T70]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   19.620277][   T70]  ? netdev_notify_peers (net/core/dev.c:1891)
[   19.620536][   T70]  ? netif_close_many (net/core/dev.c:1959)
[   19.620800][   T70]  netif_close_many (net/core/dev.c:1959)
[   19.621058][   T70]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   19.621346][   T70]  ? __dev_close_many (net/core/dev.c:1949)
[   19.621603][   T70]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   19.621923][   T70]  ? trace_contention_end (./include/trace/events/lock.h:122 (discriminator 21))
[   19.622360][   T70]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   19.622672][   T70]  ? default_device_exit_batch (net/core/dev.c:13215)
[   19.622939][   T70]  ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3189 kernel/locking/mutex.h:47 kernel/locking/mutex.c:67)
[   19.623196][   T70]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   19.623574][   T70]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   19.623830][   T70]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   19.624147][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.624576][   T70]  ? unregister_netdevice_many (net/core/dev.c:12441)
[   19.624847][   T70]  default_device_exit_batch (net/core/dev.c:13229)
[   19.625111][   T70]  ? unregister_netdev (net/core/dev.c:13204)
[   19.625377][   T70]  ops_undo_list (net/core/net_namespace.c:251)
[   19.625813][   T70]  ? rtnl_net_dumpid_one (net/core/net_namespace.c:223)
[   19.626034][   T70]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   19.626296][   T70]  cleanup_net (net/core/net_namespace.c:698)
[   19.626556][   T70]  ? net_passive_dec (net/core/net_namespace.c:660)
[   19.626951][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.627195][   T70]  process_one_work (kernel/workqueue.c:3268)
[   19.627475][   T70]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   19.627735][   T70]  ? assign_work (kernel/workqueue.c:1206)
[   19.628174][   T70]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   19.628412][   T70]  ? rescuer_thread (kernel/workqueue.c:3373)
[   19.628675][   T70]  kthread (kernel/kthread.c:463)
[   19.628874][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.629134][   T70]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   19.629511][   T70]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   19.629772][   T70]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   19.630031][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   19.630287][   T70]  ret_from_fork (arch/x86/kernel/process.c:164)
[   19.630714][   T70]  ? kthread_is_per_cpu (kernel/kthread.c:412)


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