loop0: rw=0, want=18442984958116442982, limit=116
attempt to access beyond end of device
loop0: rw=0, want=18442984958116442984, limit=116
attempt to access beyond end of device
loop0: rw=0, want=18442984958116442986, limit=116
INFO: task kworker/u4:0:6 blocked for more than 140 seconds.
      Not tainted 4.9.111-g03c70fe #6
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:0    D24424     6      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801d9a38000 ffff8801bc3fcfc0 ffff8801bb5d24c0 ffff8801cd8bc800
 ffff8801db321c18 ffff8801d9a47908 ffffffff839e7ded ffff8801d9a388c8
 ffffed003b347118 ffff8801d9a38000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839e93ef>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839e9d73>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839ee1f6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839ee1f6>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff82123ead>] flush_echoes drivers/tty/n_tty.c:799 [inline]
 [<ffffffff82123ead>] __receive_buf drivers/tty/n_tty.c:1617 [inline]
 [<ffffffff82123ead>] n_tty_receive_buf_common+0xcfd/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff821254e3>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8212afdf>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212bfe3>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212bfe3>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118d131>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df26>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d05d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f8e9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
6 locks held by kworker/u4:0/6:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d03e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d03e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d03e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d03e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118d078>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff821297b0>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:296
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8212be16>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8212323b>] n_tty_receive_buf_common+0x8b/0x2300 drivers/tty/n_tty.c:1674
 #5:  (&ldata->output_lock){+.+...}, at: [<ffffffff82123ead>] flush_echoes drivers/tty/n_tty.c:799 [inline]
 #5:  (&ldata->output_lock){+.+...}, at: [<ffffffff82123ead>] __receive_buf drivers/tty/n_tty.c:1617 [inline]
 #5:  (&ldata->output_lock){+.+...}, at: [<ffffffff82123ead>] n_tty_receive_buf_common+0xcfd/0x2300 drivers/tty/n_tty.c:1711
2 locks held by khungtaskd/520:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813666fc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813666fc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425d87>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3758:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f6e92>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211e602>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
4 locks held by syz-executor3/24855:
 #0:  (&tty->legacy_mutex){+.+.+.}, at: [<ffffffff8212ef5a>] tty_lock+0x6a/0xd0 drivers/tty/tty_mutex.c:18
 #1:  (&tty->legacy_mutex/1){+.+.+.}, at: [<ffffffff8212ef5a>] tty_lock+0x6a/0xd0 drivers/tty/tty_mutex.c:18
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff821297b0>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:296
 #3:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8211c351>] n_tty_flush_buffer+0x21/0x310 drivers/tty/n_tty.c:359

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

NMI backtrace for cpu 0
CPU: 0 PID: 520 Comm: khungtaskd Not tainted 4.9.111-g03c70fe #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8647d08 ffffffff81eb2729 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9af0 ffff8801d8647d40
 ffffffff81ebda27 0000000000000000 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb2729>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb2729>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebda27>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebd9ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9bf4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366c94>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366c94>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366c94>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366c94>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d05d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f8e9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 24856 Comm: syz-executor3 Not tainted 4.9.111-g03c70fe #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801cd8bc800 task.stack: ffff88018fc98000
RIP: 0010:[<ffffffff8211a490>] 
c [<ffffffff8211a490>] echo_buf drivers/tty/n_tty.c:146 [inline]
RIP: 0010:[<ffffffff8211a490>] 
c [<ffffffff8211a490>] __process_echoes+0x5b0/0x780 drivers/tty/n_tty.c:734
RSP: 0018:ffff88018fc9f8a8  EFLAGS: 00000246
RAX: 0000000000040000 RBX: ffffc90006a99000 RCX: ffffc90007cf7000
RDX: 0000000000040000 RSI: ffffffff8211a52e RDI: ffffc90006a9b0b4
RBP: ffff88018fc9f910 R08: ffff8801cd8bd138 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 000000078b1bae53
R13: 000000000000f51d R14: dffffc0000000000 R15: 000000078b1bae55
FS:  00007f4e3f745700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc043aff000 CR3: 00000001a17bb000 CR4: 00000000001606f0
DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff88018fc9f9e8
c ffffffff839f9669
c ffffc90006a9b278
c ffffed003a8f0d35
c
 ffff8801d47869ac
c ffffc90006a99020
c 0000000000000000
c ffff8801d4786600
c
 ffffc90006a99000
c ffff8801d4786600
c 000000000000f51d
c ffffc90006a9b300
c
Call Trace:
 [<ffffffff8211bdf7>] commit_echoes+0x147/0x1b0 drivers/tty/n_tty.c:766
 [<ffffffff82121054>] n_tty_receive_char_special+0xd64/0x2860 drivers/tty/n_tty.c:1286
 [<ffffffff82124a9a>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1579 [inline]
 [<ffffffff82124a9a>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82124a9a>] n_tty_receive_buf_common+0x18ea/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82125520>] n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1740
 [<ffffffff8211593f>] tiocsti drivers/tty/tty_io.c:2314 [inline]
 [<ffffffff8211593f>] tty_ioctl+0xc8f/0x2270 drivers/tty/tty_io.c:2905
 [<ffffffff815b2c6c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b2c6c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b2c6c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b3cef>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b3cef>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f8cd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
c48 
cc1 
cea 
c03 
c80 
c3c 
c02 
c00 
c0f 
c85 
c47 
c01 
c00 
c00 
c8b 
c4d 
ccc 
c4c 
c8b 
c6b 
c20 
c29 
c4d 
cc8 
c49 
cbe 
c00 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
ceb 
c03 
c<4d> 
c89 
cfc 
ce8 
c78 
c45 
c24 
cff 
c4c 
c89 
ce8 
c4c 
c29 
ce0 
c48 
c3d 
cdf 
c0e 
c00 
c00 
c0f 
c