INFO: task kworker/0:1H:52 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:1H    state:D stack:26328 pid:52    tgid:52    ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: kblockd blk_mq_requeue_work
Call Trace:
 <TASK>
 __schedule+0x17b4/0x5680
 schedule+0x164/0x360
 schedule_timeout+0x158/0x2c0
 nbd_queue_rq+0x857/0x1100
 blk_mq_dispatch_rq_list+0xa70/0x1910
 __blk_mq_sched_dispatch_requests+0xdcc/0x1600
 blk_mq_sched_dispatch_requests+0xd7/0x190
 blk_mq_run_hw_queue+0x348/0x4f0
 blk_mq_run_hw_queues+0x26c/0x3f0
 blk_mq_requeue_work+0x71c/0x780
 process_scheduled_works+0xb5d/0x1860
 worker_thread+0xa53/0xfc0
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/35:
 #0: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
4 locks held by kworker/0:1H/52:
 #0: ffff88810368b940 ((wq_completion)kblockd){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860
 #1: ffffc90000bc7c40 ((work_completion)(&(&q->requeue_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860
 #2: ffff88819ba9fb18 (set->srcu){.+.+}-{0:0}, at: blk_mq_run_hw_queue+0x31f/0x4f0
 #3: ffff888024a10778 (&cmd->lock){+.+.}-{4:4}, at: nbd_queue_rq+0xc6/0x1100
2 locks held by getty/5443:
 #0: ffff8881739d90a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900034732e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45c/0x13a0
1 lock held by udevd/19166:
 #0: ffff88811c81c350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30
1 lock held by udevd/26657:
 #0: ffff88811f2b6350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30
2 locks held by syz.1.14910/28543:
 #0: ffff8881b9253e40 (&sb->s_type->i_mutex_key#13){+.+.}-{4:4}, at: sock_close+0x9b/0x240
 #1: ffffffff8e963068 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770

=============================================

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 35 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 nmi_cpu_backtrace+0x274/0x2d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 sys_info+0x135/0x170
 watchdog+0xfd3/0x1030
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 28543 Comm: syz.1.14910 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:unwind_next_frame+0x1b76/0x2550
Code: 4c 8b 6c 24 20 41 0f b6 44 2d 00 84 c0 0f 85 81 02 00 00 41 c7 06 00 00 00 00 31 db e8 73 ad 31 0a 85 c0 74 3a e8 1a ca 33 00 <84> c0 75 31 e8 61 ad 31 0a 85 c0 74 28 80 3d 24 7a a3 0e 00 75 1f
RSP: 0018:ffffc9002d3df038 EFLAGS: 00000202
RAX: 0000000000000001 RBX: 00007f2169217d01 RCX: 0000000080000001
RDX: ffffffff90bbff00 RSI: ffffffff8c28adc0 RDI: ffffffff8c28ad80
RBP: dffffc0000000000 R08: 0000000000000022 R09: ffffffff8e95cd60
R10: ffffc9002d3df158 R11: ffffffff81b0e910 R12: 00007ffd1cda7418
R13: ffffc9002d3d8000 R14: ffffc9002d3df108 R15: ffffffff8176f256
FS:  0000555564b65500(0000) GS:ffff88818dc8d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1ce79ea2f8 CR3: 000000016fa66000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 arch_stack_walk+0x11b/0x150
 stack_trace_save+0xa9/0x100
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x93/0xb0
 __kmalloc_cache_noprof+0x31c/0x660
 nf_nat_masq_schedule+0x31f/0x6e0
 masq_inet6_event+0x153/0x1c0
 notifier_call_chain+0x1ad/0x3d0
 atomic_notifier_call_chain+0xda/0x180
 addrconf_ifdown+0xeb3/0x1a40
 addrconf_notify+0x1bc/0x1050
 notifier_call_chain+0x1ad/0x3d0
 netif_close_many+0x2ae/0x420
 unregister_netdevice_many_notify+0xb50/0x22c0
 unregister_netdevice_queue+0x31f/0x360
 __tun_detach+0x6d9/0x15d0
 tun_chr_close+0x10a/0x1c0
 __fput+0x44f/0xa60
 task_work_run+0x1d9/0x270
 exit_to_user_mode_loop+0xed/0x480
 do_syscall_64+0x33e/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2168f9cdd9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd1cda7418 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f2169217da0 RCX: 00007f2168f9cdd9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f2169217da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007f2169217cb0 R11: 0000000000000246 R12: 000000000011c030
R13: 00007f216921618c R14: 000000000011be1d R15: 00007f2169216180
 </TASK>
