INFO: task syz-executor4:7536 blocked for more than 120 seconds.
      Not tainted 4.9.71-g2506378 #113
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D29168  7536   3553 0x00000004
 ffff8801d8583000 ffff8801c2d25f80 ffff8801d8e30fc0 ffff8801c32e6000
 ffff8801db321458 ffff8801d8cf77d0 ffffffff8389e00b ffff8801d8cf77a8
 ffffffff8123940f 00ffffff838a997a ffff8801db321d28 ffff8801db321d50
Call Trace:
 [<ffffffff8389f5af>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff838a9a90>] rwsem_down_read_failed+0x1e0/0x320 kernel/locking/rwsem-xadd.c:260
 [<ffffffff81dc5448>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<ffffffff838a8812>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<ffffffff838a8812>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<ffffffff82006f47>] n_tty_read+0x217/0x16c0 drivers/tty/n_tty.c:2137
 [<ffffffff81ff5769>] tty_read+0x169/0x250 drivers/tty/tty_io.c:1079
 [<ffffffff8156a4e1>] do_loop_readv_writev.part.17+0x141/0x1e0 fs/read_write.c:714
 [<ffffffff8156e350>] do_loop_readv_writev fs/read_write.c:880 [inline]
 [<ffffffff8156e350>] do_readv_writev+0x520/0x750 fs/read_write.c:874
 [<ffffffff8156e604>] vfs_readv+0x84/0xc0 fs/read_write.c:898
 [<ffffffff8156e726>] do_readv+0xe6/0x250 fs/read_write.c:924
 [<ffffffff81571c17>] SYSC_readv fs/read_write.c:1011 [inline]
 [<ffffffff81571c17>] SyS_readv+0x27/0x30 fs/read_write.c:1008
 [<ffffffff838aef85>] entry_SYSCALL_64_fastpath+0x23/0xc6

Showing all locks held in the system:
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81371095>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81371095>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81236180>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3302:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838ad1a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82006f24>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
3 locks held by syz-executor4/7536:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838ad1a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82006f24>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
 #2:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff82006f47>] n_tty_read+0x217/0x16c0 drivers/tty/n_tty.c:2137
3 locks held by syz-executor4/7552:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838ad1a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82006f24>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133
 #2:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff82006f47>] n_tty_read+0x217/0x16c0 drivers/tty/n_tty.c:2137

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

NMI backtrace for cpu 1
CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.71-g2506378 #113
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d89c7d00 ffffffff81d922b9 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810ba190 ffff8801d89c7d38
 ffffffff81d9d3dd 0000000000000001 0000000000000000 ffff8801c396cc18
Call Trace:
 [<ffffffff81d922b9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d922b9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9d3dd>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9d517>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba284>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81371660>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81371660>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81371660>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81371660>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff8119898d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838af22a>] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 7519 Comm: syz-executor4 Not tainted 4.9.71-g2506378 #113
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d92a0000 task.stack: ffff8801d8498000
RIP: 0010:[<ffffffff8136944b>] 
c [<ffffffff8136944b>] __sanitizer_cov_trace_pc+0x2b/0x50 kernel/kcov.c:100
RSP: 0018:ffff8801d849fb28  EFLAGS: 00000246
RAX: ffff8801d92a0000 RBX: ffffc90005764060 RCX: ffffffff82004376
RDX: 0000000000000002 RSI: ffffc90002fe5000 RDI: ffffc90005765260
RBP: ffff8801d849fb28 R08: 1ffff1003b25411a R09: 0000000000000000
R10: 0000000000000003 R11: ffff8801d92a0000 R12: ffffc90005763000
R13: 00000004230e75a5 R14: 00000000203eeffc R15: ffff8801d9a85fb8
FS:  00007fa59d388700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f92803dc000 CR3: 00000001c2ef6000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d849fb78
c ffffffff82004376
c ffffffffffffffff
c 00000000000005a5
c
 0000000000000000
c ffff8801d9a85d80
c 1ffff1003b093f75
c 000000000000541b
c
 ffffffffffffffe7
c ffff8801d967b000
c ffff8801d849fd70
c ffffffff81ffd063
c
Call Trace:
 [<ffffffff82004376>] inq_canon drivers/tty/n_tty.c:2414 [inline]
 [<ffffffff82004376>] n_tty_ioctl+0x266/0x2d0 drivers/tty/n_tty.c:2431
 [<ffffffff81ffd063>] tty_ioctl+0x733/0x2170 drivers/tty/tty_io.c:2992
 [<ffffffff815abdda>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815abdda>] do_vfs_ioctl+0x1aa/0x1140 fs/ioctl.c:679
 [<ffffffff815acdff>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815acdff>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff838aef85>] entry_SYSCALL_64_fastpath+0x23/0xc6
Code: 
c55 
c48 
c89 
ce5 
c65 
c48 
c8b 
c04 
c25 
c40 
c55 
c01 
c00 
c65 
c8b 
c15 
c9c 
cc0 
cca 
c7e 
c81 
ce2 
c00 
c01 
c1f 
c00 
c48 
c8b 
c4d 
c08 
c75 
c2b 
c8b 
c90 
c68 
c12 
c00 
c00 
c83 
cfa 
c02 
c75 
c20 
c<48> 
c8b 
cb0 
c70 
c12 
c00 
c00 
c8b 
c80 
c6c 
c12 
c00 
c00 
c48 
c8b 
c16 
c48 
c83 
cc2 
c01 
c48 
c