INFO: task syz-executor:9340 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:18312 pid:9340  tgid:9340  ppid:1      task_flags:0x400140 flags:0x00004004
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 wb_wait_for_completion+0x15f/0x260
 __writeback_inodes_sb_nr+0x1f6/0x250
 sync_filesystem+0xa3/0x230
 generic_shutdown_super+0x6f/0x2c0
 bch2_kill_sb+0x41/0x50
 deactivate_locked_super+0xbc/0x130
 cleanup_mnt+0x425/0x4c0
 task_work_run+0x1d4/0x260
 exit_to_user_mode_loop+0xec/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1572f8ff17
RSP: 002b:00007ffcd827c798 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f1573011c05 RCX: 00007f1572f8ff17
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffcd827c850
RBP: 00007ffcd827c850 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffcd827d8e0
R13: 00007f1573011c05 R14: 000000000003fc87 R15: 00007ffcd827d920
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u8:0/12:
1 lock held by khungtaskd/34:
 #0: ffffffff8e139ee0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by kworker/u9:6/1090:
 #0: ffff88801aff7148 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90006d57bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
2 locks held by getty/5680:
 #0: ffff8880235590a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900029062f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
1 lock held by syz-executor/9340:
 #0: ffff88803f1740e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super+0xa9/0xe0
6 locks held by kworker/1:7/10873:
 #0: ffff88801b75c148 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc900046afbc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff888024018198 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a20
 #3: ffff88811bf85198 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400
 #4: ffff88811f2ed160 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400
 #5: ffff888116ba5a20 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400
1 lock held by syz.2.1097/13382:
 #0: ffffffff8e13f978 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3b9/0x730
1 lock held by dhcpcd/13400:
 #0: ffff88804062c408 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: sock_close+0x9b/0x240

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 34 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+0x189/0x250
 nmi_cpu_backtrace+0x39e/0x3d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 watchdog+0xf93/0xfe0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 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: 13382 Comm: syz.2.1097 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+0x117c/0x2390
Code: 0f b6 04 2f 84 c0 0f 85 f9 0f 00 00 c6 03 00 4c 8b 64 24 10 4c 8b 7c 24 28 48 8b 44 24 40 0f b6 04 28 84 c0 0f 85 8a 0d 00 00 <41> 0f b6 04 2f 84 c0 0f 85 a1 0d 00 00 0f b7 32 c1 ee 04 83 e6 0f
RSP: 0018:ffffc90003537538 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffc90003537640 RCX: 0000000000000000
RDX: ffffffff9037887a RSI: 0000000000000000 RDI: ffffc90003537668
RBP: dffffc0000000000 R08: ffffc90003537667 R09: 0000000000000000
R10: ffffc90003537658 R11: fffff520006a6ecd R12: ffffc90003537ef0
R13: ffffc90003537658 R14: ffffc90003537608 R15: 1ffffffff206f10f
FS:  0000555568459500(0000) GS:ffff8880b861b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005606e982c680 CR3: 000000000df36000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 arch_stack_walk+0x11c/0x150
 stack_trace_save+0x9c/0xe0
 save_stack+0xf5/0x1f0
 __reset_page_owner+0x71/0x1f0
 __free_frozen_pages+0xbc4/0xd30
 vfree+0x25a/0x400
 kcov_close+0x28/0x50
 __fput+0x44c/0xa70
 task_work_run+0x1d4/0x260
 do_exit+0x6b5/0x2300
 do_group_exit+0x21c/0x2d0
 get_signal+0x1286/0x1340
 arch_do_signal_or_restart+0x9a/0x750
 exit_to_user_mode_loop+0x75/0x110
 do_syscall_64+0x2bd/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f687098ebe9
Code: Unable to access opcode bytes at 0x7f687098ebbf.
RSP: 002b:00007ffe6f278018 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffdfc RBX: 0000000000067b9d RCX: 00007f687098ebe9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f6870bc5fac
RBP: 000000000000015e R08: 7fffffffffffffff R09: 000000086f27830f
R10: 00007ffe6f278110 R11: 0000000000000246 R12: 00007f6870bc5fac
R13: 00007ffe6f278110 R14: 0000000000067cfb R15: 00007ffe6f278130
 </TASK>
