keychord: Insufficient bytes present for keycount 0
keychord: Insufficient bytes present for keycount 2
INFO: task kworker/u4:1:22 blocked for more than 120 seconds.
      Not tainted 4.9.109-g7cecc75 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:1    D25352    22      2 0x00000000
Workqueue: events_unbound flush_to_ldisc
 ffff8801d9bd0000 0000000000000000 ffff8801ccabc540 ffff8801d6ef3000
 ffff8801db321c18 ffff8801d9be78c8 ffffffff839e8a3d ffff8801d9bd08c8
 ffffed003b37a118 ffff8801d9bd0000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea03f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839ea9c3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839eee46>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839eee46>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff8211d4b0>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764
 [<ffffffff82126108>] n_tty_receive_char_fast drivers/tty/n_tty.c:1418 [inline]
 [<ffffffff82126108>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1578 [inline]
 [<ffffffff82126108>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff82126108>] n_tty_receive_buf_common+0x1878/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82126bc3>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8212c6bf>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212d6c3>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212d6c3>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118d121>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df16>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9adc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
6 locks held by kworker/u4:1/22:
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8118d02e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((&buf->work)){+.+...}, at: [<ffffffff8118d068>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8212ae90>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:296
 #3:  (&port->buf.lock/1){+.+...}, at: [<ffffffff8212d4f6>] flush_to_ldisc+0x86/0x370 drivers/tty/tty_buffer.c:505
 #4:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8212491b>] n_tty_receive_buf_common+0x8b/0x2300 drivers/tty/n_tty.c:1674
 #5:  (&ldata->output_lock){+.+...}, at: [<ffffffff8211d4b0>] commit_echoes+0x120/0x1b0 drivers/tty/n_tty.c:764
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425cb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3768:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7ae2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211fce2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
3 locks held by syz-executor6/10142:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7ae2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8212ae90>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:296
 #2:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8211da31>] n_tty_flush_buffer+0x21/0x310 drivers/tty/n_tty.c:359

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

NMI backtrace for cpu 0
CPU: 0 PID: 519 Comm: khungtaskd Not tainted 4.9.109-g7cecc75 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d960fd08 ffffffff81eb3e29 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b9580 ffff8801d960fd40
 ffffffff81ebf127 0000000000000000 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf127>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf0ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9684>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366bc4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366bc4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366bc4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366bc4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9adc>] 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: 10105 Comm: syz-executor6 Not tainted 4.9.109-g7cecc75 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d628b000 task.stack: ffff8801d5270000
RIP: 0010:[<ffffffff8135e96b>] 
c [<ffffffff8135e96b>] __sanitizer_cov_trace_pc+0x2b/0x50 kernel/kcov.c:100
RSP: 0018:ffff8801d5277898  EFLAGS: 00000246
RAX: ffff8801d628b000 RBX: ffffc900007f6000 RCX: ffffc900114b8000
RDX: 0000000000000002 RSI: ffffffff8211bb8f RDI: ffffc900007f7451
RBP: ffff8801d5277898 R08: ffff8801d628b938 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000006ad0141f2
R13: 000000000000428f R14: dffffc0000000000 R15: 00000006ad0141f2
FS:  00007f897e8e7700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f079e3939b8 CR3: 00000001bb563000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d5277910
c ffffffff8211bb8f
c 0000000000000000
c ffffc900007f6000
c
 ffffc900007f8278
c ffffed00398baa05
c ffff8801cc5d502c
c ffffc900007f6020
c
 0000000000000400
c ffff8801cc5d4c80
c ffffc900007f6000
c ffff8801cc5d4c80
c
Call Trace:
 [<ffffffff8211bb8f>] echo_buf drivers/tty/n_tty.c:146 [inline]
 [<ffffffff8211bb8f>] __process_echoes+0x5cf/0x780 drivers/tty/n_tty.c:734
 [<ffffffff8211d4d7>] commit_echoes+0x147/0x1b0 drivers/tty/n_tty.c:766
 [<ffffffff82122734>] n_tty_receive_char_special+0xd64/0x2860 drivers/tty/n_tty.c:1286
 [<ffffffff8212617a>] n_tty_receive_buf_fast drivers/tty/n_tty.c:1579 [inline]
 [<ffffffff8212617a>] __receive_buf drivers/tty/n_tty.c:1613 [inline]
 [<ffffffff8212617a>] n_tty_receive_buf_common+0x18ea/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82126c00>] n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1740
 [<ffffffff8211701f>] tiocsti drivers/tty/tty_io.c:2314 [inline]
 [<ffffffff8211701f>] tty_ioctl+0xc8f/0x2270 drivers/tty/tty_io.c:2905
 [<ffffffff815b2b9c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b2b9c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b2b9c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b3c1f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b3c1f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9913>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
c55 
c48 
c89 
ce5 
c65 
c48 
c8b 
c04 
c25 
cc0 
c7d 
c01 
c00 
c65 
c8b 
c15 
cfc 
c93 
ccb 
c7e 
c81 
ce2 
c00 
c01 
c1f 
c00 
c48 
c8b 
c75 
c08 
c75 
c2b 
c8b 
c90 
c80 
c12 
c00 
c00 
c83 
cfa 
c02 
c75 
c20 
c<48> 
c8b 
c88 
c88 
c12 
c00 
c00 
c8b 
c80 
c84 
c12 
c00 
c00 
c48 
c8b 
c11 
c48 
c83 
cc2 
c01 
c48 
c