INFO: task syz-executor.2:29230 blocked for more than 140 seconds.
      Not tainted 4.9.141+ #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D29592 29230   2118 0x00000000
 ffff8801c6420000 ffff8801cc522100 ffff8801d3bfa680 ffff8801cf1e8000
 ffff8801db721018 ffff8801d78b7840 ffffffff828075c2 ffff8801d3bfa680
 ffffffff83cd9180 ffff8801d78b7860 000000000000342d ffff8801db7218f0
Call Trace:
 [<ffffffff82808aef>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff828142d5>] schedule_timeout+0x735/0xe20 kernel/time/timer.c:1771
 [<ffffffff81d4312c>] down_read_failed drivers/tty/tty_ldsem.c:241 [inline]
 [<ffffffff81d4312c>] __ldsem_down_read_nested+0x33c/0x610 drivers/tty/tty_ldsem.c:332
 [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 [<ffffffff81d3ca85>] tty_ldisc_ref_wait+0x25/0x80 drivers/tty/tty_ldisc.c:275
 [<ffffffff81d28626>] tty_ioctl+0x3b6/0x2190 drivers/tty/tty_io.c:3009
 [<ffffffff81546dec>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff81546dec>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff81546dec>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff81547e6f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff81547e6f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff810056ef>] do_syscall_64+0x19f/0x550 arch/x86/entry/common.c:285
 [<ffffffff82817893>] 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: [<ffffffff8131c0cc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8131c0cc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff813fe63f>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/2026:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d37362>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor.2/29103:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d37362>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor.2/29230:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
2 locks held by syz-executor.2/29231:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff82815952>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81d37362>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.141+ #1
 ffff8801d9907d08 ffffffff81b42e79 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810983b0 ffff8801d9907d40
 ffffffff81b4df89 0000000000000000 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81b42e79>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b42e79>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81b4df89>] nmi_cpu_backtrace.cold.0+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81b4df1c>] nmi_trigger_cpumask_backtrace+0x12c/0x151 lib/nmi_backtrace.c:60
 [<ffffffff810984b4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8131c65d>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8131c65d>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8131c65d>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8131c65d>] watchdog+0x6ad/0xa20 kernel/hung_task.c:239
 [<ffffffff81142c3d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff82817a5c>] 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: 4410 Comm: syz-executor.0 Not tainted 4.9.141+ #1
task: ffff8801d5c0af80 task.stack: ffff8801c67c0000
RIP: 0010:[<ffffffff81243c4b>] 
c [<ffffffff81243c4b>] debug_lockdep_rcu_enabled+0x3b/0x90 kernel/rcu/update.c:264
RSP: 0000:ffff8801c67c7b70  EFLAGS: 00000002
RAX: 0000000000000007 RBX: ffff8801d5c0af80 RCX: ffffc9000092f000
RDX: 0000000000000002 RSI: ffffffff81108a99 RDI: ffffffff833e7adc
RBP: ffff8801c67c7b70 R08: ffff8801d5c0b830 R09: 021ea93223d1fec7
R10: ffff8801d5c0af80 R11: 0000000000000001 R12: ffff8801d5c0b6e0
R13: ffff8801c5b22000 R14: ffff8801c5b22000 R15: ffff8801d1bdcee0
FS:  00007f1c13b32700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffeeffffff36 CR3: 00000001c7a4d000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Stack:
 ffff8801c67c7be8
c ffffffff81108ac7
c ffffffff811089f8
c 0000000000000046
c
 ffff8801d5c0b670
c 0000000a8110b164
c ffff8801d5c0b6f0
c ffff8801d5c0b6c0
c
 ffff8801c67c7cd0
c 0000000b00000000
c ffff8801c67c7cd0
c ffff8801d5c0af80
c
Call Trace:
 [<ffffffff81108ac7>] rcu_read_unlock include/linux/rcupdate.h:927 [inline]
 [<ffffffff81108ac7>] userns_fixup_signal_uid kernel/signal.c:964 [inline]
 [<ffffffff81108ac7>] __send_signal+0x8e7/0x1200 kernel/signal.c:1056
 [<ffffffff8110942a>] send_signal+0x4a/0xc0 kernel/signal.c:1096
 [<ffffffff8110b31a>] specific_send_sig_info kernel/signal.c:1141 [inline]
 [<ffffffff8110b31a>] force_sig_info+0x20a/0x310 kernel/signal.c:1189
 [<ffffffff810b1477>] force_sig_info_fault.constprop.7+0x177/0x290 arch/x86/mm/fault.c:244
 [<ffffffff810b1f0b>] __bad_area_nosemaphore+0x19b/0x290 arch/x86/mm/fault.c:899
 [<ffffffff810b2033>] bad_area_nosemaphore+0x33/0x40 arch/x86/mm/fault.c:914
 [<ffffffff810b2c7a>] __do_page_fault+0x54a/0xa60 arch/x86/mm/fault.c:1338
 [<ffffffff810b31e7>] do_page_fault+0x27/0x30 arch/x86/mm/fault.c:1469
 [<ffffffff828188b5>] page_fault+0x25/0x30 arch/x86/entry/entry_64.S:951
Code: 
cff 
cdf 
c48 
c89 
cfa 
c48 
c89 
ce5 
c48 
cc1 
cea 
c03 
c0f 
cb6 
c14 
c02 
c48 
c89 
cf8 
c83 
ce0 
c07 
c83 
cc0 
c03 
c38 
cd0 
c7c 
c04 
c84 
cd2 
c75 
c4c 
c8b 
c15 
c95 
c3e 
c1a 
c02 
c85 
cd2 
c74 
c3e 
c<48> 
cc7 
cc7 
c00 
c25 
c1f 
c83 
c48 
cb8 
c00 
c00 
c00 
c00 
c00 
cfc 
cff 
cdf 
c48 
c89 
cfa 
c48 
c