INFO: task syz-executor4:4492 blocked for more than 120 seconds.
      Not tainted 4.9.69-g3f1d77c #108
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D27984  4492   3562 0x00000004
 ffff8801c9620000 ffff8801d4f4ef40 ffff8801d4f4ef40 ffff8801c2833000
 ffff8801db321418 ffff8801cc65f7d0 ffffffff8389932b ffff8801cc65f7a8
 ffffffff8123886f 00ffffff838a4c9a ffff8801db321ce8 ffff8801db321d10
Call Trace:
 [<ffffffff8389a8cf>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff838a4db0>] rwsem_down_read_failed+0x1e0/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81dc3bb8>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff838a3b32>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff838a3b32>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff820020a7>] n_tty_read+0x217/0x16c0 drivers/tty/n_tty.c:2137
 [<ffffffff81ff08f9>] tty_read+0x169/0x250 drivers/tty/tty_io.c:1079
 [<ffffffff81568ef1>] do_loop_readv_writev.part.17+0x141/0x1e0 fs/read_write.c:714
 [<ffffffff8156cd60>] do_loop_readv_writev fs/read_write.c:880 [inline]
 [<ffffffff8156cd60>] do_readv_writev+0x520/0x750 fs/read_write.c:874
 [<ffffffff8156d014>] vfs_readv+0x84/0xc0 fs/read_write.c:898
 [<ffffffff8156d136>] do_readv+0xe6/0x250 fs/read_write.c:924
 [<ffffffff81570627>] SYSC_readv fs/read_write.c:1011 [inline]
 [<ffffffff81570627>] SyS_readv+0x27/0x30 fs/read_write.c:1008
 [<ffffffff838aab05>] entry_SYSCALL_64_fastpath+0x23/0xc6

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe15>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136fe15>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff812355e0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3302:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8cf2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82002084>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
3 locks held by syz-executor4/4492:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838a8cf2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82002084>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
 #2:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff820020a7>] n_tty_read+0x217/0x16c0 drivers/tty/n_tty.c:2137

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.69-g3f1d77c #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d893fd00 ffffffff81d90a29 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810ba1a0 ffff8801d893fd38
 ffffffff81d9bb4d 0000000000000000 0000000000000000 ffff8801d6e41c18
Call Trace:
 [<ffffffff81d90a29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d90a29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9bb4d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9bc87>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba294>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff813703e0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff813703e0>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff813703e0>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff813703e0>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811985ed>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838aadaa>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4508 Comm: syz-executor4 Not tainted 4.9.69-g3f1d77c #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c356b000 task.stack: ffff8801c33b8000
RIP: 0010:[<ffffffff813681e9>] 
c [<ffffffff813681e9>] preempt_count arch/x86/include/asm/preempt.h:22 [inline]
RIP: 0010:[<ffffffff813681e9>] 
c [<ffffffff813681e9>] __sanitizer_cov_trace_pc+0x19/0x60 kernel/kcov.c:64
RSP: 0018:ffff8801c33bfb28  EFLAGS: 00000286
RAX: ffff8801c356b000 RBX: ffffc90004c1d060 RCX: ffffc900022f9000
RDX: 0000000080000000 RSI: 00000000d3dbb25b RDI: ffffc90004c1e260
RBP: ffff8801c33bfb28 R08: 1ffff100386ad71a R09: 0000000000000000
R10: 0000000000000003 R11: ffff8801c356b000 R12: ffffc90004c1c000
R13: 00000005ad7002f6 R14: 0000000020fe6000 R15: ffff8801c9633db8
FS:  00007faae8d61700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8dcc39a000 CR3: 00000001cd764000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801c33bfb78
c ffffffff81fff4d6
c ffffffffffffeff9
c 00000000000002f6
c
 0000000000000000
c ffff8801c9633b80
c 1ffff10038677f75
c 000000000000541b
c
 ffffffffffffffe7
c ffff8801a6e72e00
c ffff8801c33bfd70
c ffffffff81ff81f3
c
Call Trace:
 [<ffffffff81fff4d6>] inq_canon drivers/tty/n_tty.c:2414 [inline]
 [<ffffffff81fff4d6>] n_tty_ioctl+0x266/0x2d0 drivers/tty/n_tty.c:2431
 [<ffffffff81ff81f3>] tty_ioctl+0x733/0x2170 drivers/tty/tty_io.c:2992
 [<ffffffff815aa7da>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815aa7da>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815ab7ff>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815ab7ff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838aab05>] entry_SYSCALL_64_fastpath+0x23/0xc6
Code: 
ce9 
c29 
cff 
cff 
cff 
c66 
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c84 
c00 
c00 
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c00 
c55 
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c48 
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c04 
c25 
c40 
c55 
c01 
c00 
c48 
c85 
cc0 
c48 
c89 
ce5 
c74 
c1a 
c65 
c8b 
c15 
ce7 
cd2 
cca 
c7e 
c<81> 
ce2 
c00 
c01 
c1f 
c00 
c75 
c0b 
c8b 
c90 
c68 
c12 
c00 
c00 
c83 
cfa 
c01 
c74 
c02 
c5d 
cc3 
c