INFO: task syz-executor6:15616 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-executor6   D29184 15616   3575 0x00000004
 ffff8801d0c39800 0000000000000000 ffff8801d8f4b9c0 ffff8801da2cb000
 ffff8801db321458 ffff8801d5517740 ffffffff8389e00b ffff8801d5517718
 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
 [<ffffffff8200f6b5>] set_termios+0xf5/0x670 drivers/tty/tty_ioctl.c:592
 [<ffffffff82010561>] tty_mode_ioctl+0x931/0x9c0 drivers/tty/tty_ioctl.c:970
 [<ffffffff82010690>] n_tty_ioctl_helper+0x40/0x360 drivers/tty/tty_ioctl.c:1161
 [<ffffffff82004258>] n_tty_ioctl+0x148/0x2d0 drivers/tty/n_tty.c:2437
 [<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

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #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/3304:
 #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 locks held by syz-executor6/15616:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838ad1a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff8200f6b5>] set_termios+0xf5/0x670 drivers/tty/tty_ioctl.c:592
2 locks held by syz-executor6/15620:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838ad1a2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&o_tty->termios_rwsem/1){++++.+}, at: [<ffffffff8200f6b5>] set_termios+0xf5/0x670 drivers/tty/tty_ioctl.c:592

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

NMI backtrace for cpu 0
CPU: 0 PID: 514 Comm: khungtaskd Not tainted 4.9.71-g2506378 #113
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8977d00 ffffffff81d922b9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810ba190 ffff8801d8977d38
 ffffffff81d9d3dd 0000000000000000 0000000000000000 ffff8801d59f3418
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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 15606 Comm: syz-executor6 Not tainted 4.9.71-g2506378 #113
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d193c800 task.stack: ffff8801d1a90000
RIP: 0010:[<ffffffff8136945b>] 
c [<ffffffff8136945b>] __read_once_size include/linux/compiler.h:243 [inline]
RIP: 0010:[<ffffffff8136945b>] 
c [<ffffffff8136945b>] __sanitizer_cov_trace_pc+0x3b/0x50 kernel/kcov.c:105
RSP: 0018:ffff8801d1a97b28  EFLAGS: 00000246
RAX: 0000000000010000 RBX: ffffc9000008a060 RCX: ffffffff82004376
RDX: 000000000000ffff RSI: ffffc90003c63000 RDI: ffffc9000008b260
RBP: ffff8801d1a97b28 R08: 1ffff1003a327a1a R09: 0000000000000000
R10: 0000000000000003 R11: ffff8801d193c800 R12: ffffc90000089000
R13: 00000005f130a0c0 R14: 0000000020a72000 R15: ffff8801c321dfb8
FS:  00007fe17ccda700(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8509ee2000 CR3: 00000001b057e000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801d1a97b78
c ffffffff82004376
c ffffffffffffffff
c 00000000000000c0
c
 0000000000000000
c ffff8801c321dd80
c 1ffff1003a352f75
c 000000000000541b
c
 ffffffffffffffe7
c ffff8801d4ddcc00
c ffff8801d1a97d70
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: 
c9c 
cc0 
cca 
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c81 
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c00 
c01 
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c00 
c48 
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c12 
c00 
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c75 
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c48 
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c12 
c00 
c00 
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c12 
c00 
c00 
c48 
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c16 
c<48> 
c83 
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c01 
c48 
c39 
cd0 
c76 
c07 
c48 
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c0c 
cd6 
c48 
c89 
c16 
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cc3 
c0f 
c1f 
c00 
c