random: crng init done
INFO: task syz-executor468:4187 blocked for more than 120 seconds.
      Not tainted 4.9.96-g71fce1e #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor468 D28920  4187   3860 0x00000002
 ffff8801b5b26000 ffff8801b5611a40 ffff8801da0f2f40 ffff8801b8344800
 ffff8801db321b98 ffff8801d7787568 ffffffff839e240d ffffffff81233817
 0000000000000000 ffff8801b5b268c0 0000000600000007 ffff8801db322468
Call Trace:
 [<ffffffff839e3a0f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839ef048>] __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:526 [inline]
 [<ffffffff839ef048>] rwsem_down_write_failed+0x598/0x990 kernel/locking/rwsem-xadd.c:555
 [<ffffffff81ee4e77>] call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:105
 [<ffffffff839ece1c>] __down_write arch/x86/include/asm/rwsem.h:125 [inline]
 [<ffffffff839ece1c>] down_write+0x5c/0xa0 kernel/locking/rwsem.c:54
 [<ffffffff8211a4e1>] n_tty_flush_buffer+0x21/0x310 drivers/tty/n_tty.c:359
 [<ffffffff821286b9>] tty_ldisc_hangup+0x89/0x5b0 drivers/tty/tty_ldisc.c:659
 [<ffffffff8210fb37>] __tty_hangup.part.22+0x5f7/0xb00 drivers/tty/tty_io.c:744
 [<ffffffff82110061>] __tty_hangup drivers/tty/tty_io.c:694 [inline]
 [<ffffffff82110061>] tty_vhangup+0x21/0x30 drivers/tty/tty_io.c:817
 [<ffffffff8212ff34>] pty_close+0x374/0x4d0 drivers/tty/pty.c:74
 [<ffffffff82111c70>] tty_release+0x370/0xd00 drivers/tty/tty_io.c:1813
 [<ffffffff81575b13>] __fput+0x263/0x700 fs/file_table.c:208
 [<ffffffff81576035>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8119603c>] task_work_run+0x10c/0x180 kernel/task_work.c:116
 [<ffffffff8113ec91>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff8113ec91>] do_exit+0x9e1/0x27c0 kernel/exit.c:837
 [<ffffffff81144d91>] do_group_exit+0x111/0x340 kernel/exit.c:941
 [<ffffffff81167b8f>] get_signal+0x4cf/0x1450 kernel/signal.c:2317
 [<ffffffff810524d7>] do_signal+0x87/0x19f0 arch/x86/kernel/signal.c:807
 [<ffffffff81005581>] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:157
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff839f3313>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/518:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646ec>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646ec>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423ce0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3778:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f14b2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211c792>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
4 locks held by syz-executor468/4187:
 #0:  (&tty->legacy_mutex){+.+.+.}, at: [<ffffffff8212d0fa>] tty_lock+0x6a/0xd0 drivers/tty/tty_mutex.c:18
 #1:  (&tty->legacy_mutex/1){+.+...}, at: [<ffffffff8212d0fa>] tty_lock+0x6a/0xd0 drivers/tty/tty_mutex.c:18
 #2:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82127940>] tty_ldisc_ref+0x20/0x80 drivers/tty/tty_ldisc.c:297
 #3:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff8211a4e1>] n_tty_flush_buffer+0x21/0x310 drivers/tty/n_tty.c:359

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

NMI backtrace for cpu 0
CPU: 0 PID: 518 Comm: khungtaskd Not tainted 4.9.96-g71fce1e #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85f7d08 ffffffff81eb0b69 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b7d60 ffff8801d85f7d40
 ffffffff81ebbe97 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb0b69>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb0b69>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebbe97>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebbe2a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7e64>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364c84>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364c84>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364c84>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364c84>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f34dc>] 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: 45 Comm: kworker/u4:2 Not tainted 4.9.96-g71fce1e #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
c
task: ffff8801d9580000 task.stack: ffff8801d9588000
RIP: 0010:[<ffffffff8135ca1e>] 
c [<ffffffff8135ca1e>] __sanitizer_cov_trace_pc+0x1e/0x50 kernel/kcov.c:96
RSP: 0018:ffff8801d958f9c8  EFLAGS: 00000246
RAX: ffff8801d9580000 RBX: ffffc900016b4000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff821186be RDI: ffffc900016b5b31
RBP: ffff8801d958f9c8 R08: ffff8801d95809b0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000009cb6888d0
R13: 0000000000003b54 R14: dffffc0000000000 R15: 00000000000008d1
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f908de7c000 CR3: 00000001cdf01000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d958fa40
c ffffffff821186be
c 0000000000000206
c ffff8801d958f9f8
c
 ffffc900016b6278
c ffffed003af56e45
c ffff8801d7ab722c
c ffffc900016b4020
c
 00000001000008ff
c ffff8801d7ab6e80
c ffffc900016b6300
c ffffc900016b4000
c
Call Trace:
 [<ffffffff821186be>] __process_echoes+0x64e/0x780 drivers/tty/n_tty.c:738
 [<ffffffff82122074>] flush_echoes drivers/tty/n_tty.c:801 [inline]
 [<ffffffff82122074>] __receive_buf drivers/tty/n_tty.c:1617 [inline]
 [<ffffffff82122074>] n_tty_receive_buf_common+0xd34/0x2300 drivers/tty/n_tty.c:1711
 [<ffffffff82123673>] n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1746
 [<ffffffff8212917f>] tty_ldisc_receive_buf+0xaf/0x190 drivers/tty/tty_buffer.c:455
 [<ffffffff8212a183>] receive_buf drivers/tty/tty_buffer.c:474 [inline]
 [<ffffffff8212a183>] flush_to_ldisc+0x253/0x370 drivers/tty/tty_buffer.c:533
 [<ffffffff8118ae31>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118bc26>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ad5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f34dc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Code: 
c66 
c2e 
c0f 
c1f 
c84 
c00 
c00 
c00 
c00 
c00 
c0f 
c1f 
c00 
c55 
c48 
c89 
ce5 
c65 
c48 
c8b 
c04 
c25 
c40 
c7d 
c01 
c00 
c65 
c8b 
c15 
cbc 
cb2 
ccb 
c7e 
c81 
ce2 
c00 
c01 
c1f 
c00 
c48 
c8b 
c75 
c08 
c<75> 
c2b 
c8b 
c90 
c80 
c12 
c00 
c00 
c83 
cfa 
c02 
c75 
c20 
c48 
c8b 
c88 
c88 
c12 
c00 
c00 
c8b 
c