======================================
| [   38.823088][   T12] ==================================================================
| [   38.823414][   T12] 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)
| [   38.823724][   T12] Write of size 8 at addr 0000000000000000 by task kworker/u16:0/12
| [   38.823994][   T12]
[   38.824113][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   38.824120][   T12] Workqueue: netns cleanup_net
[   38.824128][   T12] Call Trace:
[   38.824131][   T12]  <TASK>
[   38.824134][   T12]  dump_stack_lvl (lib/dump_stack.c:123)
[   38.824142][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   38.824147][   T12]  kasan_report (mm/kasan/report.c:597)
[   38.824154][   T12]  ? try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   38.824160][   T12]  kasan_check_range (mm/kasan/generic.c:194 mm/kasan/generic.c:200)
[   38.824163][   T12]  try_to_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072)
[   38.824169][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   38.824172][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   38.824176][   T12]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   38.824184][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[   38.824188][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   38.824194][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[   38.824197][   T12]  ? netif_close_many (net/core/dev.c:1959)
[   38.824202][   T12]  netif_close_many (net/core/dev.c:1959)
[   38.824205][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   38.824211][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[   38.824214][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   38.824219][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   38.824223][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   38.824228][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   38.824233][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   38.824237][   T12]  ? lockdep_rtnl_is_held (net/core/rtnetlink.c:182)
[   38.824240][   T12]  ? sit_exit_rtnl_net (net/ipv6/sit.c:1814 (discriminator 1))
[   38.824255][   T12]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[   38.824270][   T12]  ? netns_get (net/core/net_namespace.c:223)
[   38.824274][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   38.824278][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   38.824282][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   38.824285][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.824292][   T12]  process_one_work (kernel/workqueue.c:3268)
[   38.824298][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   38.824304][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   38.824308][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   38.824314][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   38.824317][   T12]  kthread (kernel/kthread.c:463)
[   38.824322][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.824325][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   38.824332][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   38.824338][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.824341][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.824344][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   38.824347][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.824350][   T12]  ret_from_fork_asm (arch/x86/entry/entry_64.S:255)
| [   38.834251][   T12] #PF: error_code(0x0002) - not-present page
| [   38.834488][   T12] PGD 0 P4D 0
| [   38.834632][   T12] Oops: Oops: 0002 [#1] SMP KASAN
| [   38.835191][   T12] Tainted: [B]=BAD_PAGE
[   38.835323][   T12] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   38.835533][   T12] Workqueue: netns cleanup_net
[   38.835715][   T12] 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)
[   38.835940][   T12] 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 df 81 84 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 df 81 84 00       	call   0x848209
  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
[   38.836545][   T12] RSP: 0018:ffffc900000c7730 EFLAGS: 00010046
[   38.836783][   T12] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff8fc40aaa
[   38.837036][   T12] RDX: fffffbfff27cfecd RSI: 0000000000000008 RDI: ffffffff93e7f660
[   38.837281][   T12] RBP: ffffc900000c7798 R08: 0000000000000001 R09: fffffbfff27cfecc
[   38.837531][   T12] R10: ffffffff93e7f667 R11: ffffc900000c7200 R12: 0000000000000000
[   38.837796][   T12] R13: 0000000000000286 R14: ffff88800bca9000 R15: dffffc0000000000
[   38.838063][   T12] FS:  0000000000000000(0000) GS:ffff8880a23ec000(0000) knlGS:0000000000000000
[   38.838368][   T12] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   38.838577][   T12] CR2: 0000000000000000 CR3: 0000000014b35002 CR4: 0000000000772ef0
[   38.838849][   T12] PKRU: 55555554
[   38.838999][   T12] Call Trace:
[   38.839121][   T12]  <TASK>
[   38.839209][   T12]  __cancel_work (kernel/workqueue.c:2161 kernel/workqueue.c:4364)
[   38.839393][   T12]  ? enable_delayed_work (kernel/workqueue.c:4359)
[   38.839562][   T12]  ? qdisc_destroy (net/sched/sch_generic.c:1355)
[   38.839739][   T12]  __cancel_work_sync (kernel/workqueue.c:4383)
[   38.839903][   T12]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[   38.840068][   T12]  ? netdev_notify_peers (net/core/dev.c:1891)
[   38.840238][   T12]  ? netif_close_many (net/core/dev.c:1959)
[   38.840428][   T12]  netif_close_many (net/core/dev.c:1959)
[   38.840595][   T12]  ? __mutex_handoff (kernel/locking/mutex.c:88)
[   38.840771][   T12]  ? __dev_close_many (net/core/dev.c:1949)
[   38.840953][   T12]  ? netif_close_many_and_unlock (net/core/dev.c:12476)
[   38.841155][   T12]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[   38.841363][   T12]  ? rtnl_is_locked (net/core/rtnetlink.c:169)
[   38.841530][   T12]  ? unregister_netdevice_queue (net/core/dev.c:12442)
[   38.841741][   T12]  ? dev_ingress_queue_create (net/core/dev.c:12499)
[   38.841912][   T12]  ? lockdep_rtnl_is_held (net/core/rtnetlink.c:182)
[   38.842084][   T12]  ? sit_exit_rtnl_net (net/ipv6/sit.c:1814 (discriminator 1))
[   38.842266][   T12]  ops_undo_list (net/core/net_namespace.c:189 net/core/net_namespace.c:248)
[   38.842449][   T12]  ? netns_get (net/core/net_namespace.c:223)
[   38.842617][   T12]  ? cleanup_net (./include/linux/list.h:191 net/core/net_namespace.c:693)
[   38.842789][   T12]  cleanup_net (net/core/net_namespace.c:698)
[   38.842956][   T12]  ? net_passive_dec (net/core/net_namespace.c:660)
[   38.843129][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.843318][   T12]  process_one_work (kernel/workqueue.c:3268)
[   38.843490][   T12]  ? pwq_dec_nr_in_flight (kernel/workqueue.c:3165)
[   38.843657][   T12]  ? assign_work (kernel/workqueue.c:1206)
[   38.843840][   T12]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[   38.844007][   T12]  ? rescuer_thread (kernel/workqueue.c:3373)
[   38.844170][   T12]  kthread (kernel/kthread.c:463)
[   38.844307][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.844484][   T12]  ? ret_from_fork (arch/x86/kernel/process.c:157)
[   38.844655][   T12]  ? __lock_release (kernel/locking/lockdep.c:5536)
[   38.844825][   T12]  ? rcu_is_watching (./include/linux/context_tracking.h:128 kernel/rcu/tree.c:751)
[   38.844984][   T12]  ? kthread_is_per_cpu (kernel/kthread.c:412)
[   38.845142][   T12]  ret_from_fork (arch/x86/kernel/process.c:164)
[   38.845310][   T12]  ? 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