INFO: task syz-executor5:9411 blocked for more than 140 seconds.
      Not tainted 4.9.127+ #91
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D29608  9411   2117 0x00000000
 ffff88006a438000 0000000000000000 ffff8801d3db9080 ffff8801da6b2f80
 ffff8801db721018 ffff88006b2cf850 ffffffff8277dc12 0000000000000000
 ffffffff83ac66e0 0000000000000000 0000000000002dd7 ffff8801db7218f0
Call Trace:
 [<ffffffff8277f13f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff82789765>] schedule_timeout+0x735/0xe20 kernel/time/timer.c:1768
 [<ffffffff81ce9a24>] down_read_failed drivers/tty/tty_ldsem.c:241 [inline]
 [<ffffffff81ce9a24>] __ldsem_down_read_nested+0x2c4/0x4f0 drivers/tty/tty_ldsem.c:332
 [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 [<ffffffff81ce34e5>] tty_ldisc_ref_wait+0x25/0x80 drivers/tty/tty_ldisc.c:275
 [<ffffffff81cceeb6>] tty_ioctl+0x3b6/0x2190 drivers/tty/tty_io.c:3004
 [<ffffffff815276bc>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815276bc>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815276bc>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff8152873f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff8152873f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff8100554f>] do_syscall_64+0x19f/0x480 arch/x86/entry/common.c:282
 [<ffffffff8278cd13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81309d9c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81309d9c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff813e6edc>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/2031:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cddbf2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor4/6113:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cddbf2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor5/9119:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cddbf2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor5/9400:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cddbf2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor5/9411:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor2/10223:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cddbf2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor5/10271:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278ade2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cddbf2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.127+ #91
 ffff8801d9907d08 ffffffff81af11e9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810967d0 ffff8801d9907d40
 ffffffff81afbf49 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81af11e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81af11e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81afbf49>] nmi_cpu_backtrace.cold.0+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81afbedc>] nmi_trigger_cpumask_backtrace+0x12c/0x151 lib/nmi_backtrace.c:60
 [<ffffffff810968d4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8130a32d>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8130a32d>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8130a32d>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8130a32d>] watchdog+0x6ad/0xa20 kernel/hung_task.c:239
 [<ffffffff8113dd2d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff8278cedc>] 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: 2059 Comm: syz-fuzzer Not tainted 4.9.127+ #91
task: ffff8801cffd2f80 task.stack: ffff8801ce000000
RIP: 0033:[<000000000041debf>] 
c [<000000000041debf>] 0x41debf
RSP: 002b:000000c420069e80  EFLAGS: 00000293
RAX: 000000c420000000 RBX: 000000c41b9f5e50 RCX: 0000000000000002
RDX: 000000c51ae20000 RSI: 000000c4ac1435f0 RDI: 0000000000000000
RBP: 000000c420069f18 R08: 0000000000000002 R09: 0000000000b71540
R10: 0000000000000030 R11: 000000c4ac39c8a0 R12: 0000000000000001
R13: 000000c514e14360 R14: 0000000000000001 R15: 0000000000000000
FS:  000000c420058068(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c4ffd1d010 CR3: 00000001ce993000 CR4: 00000000001606b0