INFO: task syz-executor7:5687 blocked for more than 120 seconds.
      Not tainted 4.4.107-g610c835 #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D ffff8801d3de7748 28424  5687   3531 0x20020004
 ffff8801d3de7748 dffffc0000000000 ffff8801d21e0870 ffff8801d3de7728
 ffffffff8123364f ffff8801d21e0800 ffff8801db21f878 ffff8801db21f8a0
 ffff8801db21ef98 ffff8800b6ab5f00 ffff8801d21e0000 ffff8801d3de0000
Call Trace:
 [<ffffffff83765d3a>] schedule+0x9a/0x1c0 kernel/sched/core.c:3351
 [<ffffffff8376ffef>] rwsem_down_read_failed+0x1bf/0x300 kernel/locking/rwsem-xadd.c:250
 [<ffffffff81d34e44>] call_rwsem_down_read_failed+0x14/0x30 arch/x86/lib/rwsem.S:90
 [<ffffffff81f58d33>] n_tty_read+0x233/0x1cd0 drivers/tty/n_tty.c:2184
 [<ffffffff81f46b98>] tty_read+0x158/0x240 drivers/tty/tty_io.c:1071
 [<ffffffff8151b341>] do_loop_readv_writev+0x141/0x1e0 fs/read_write.c:680
 [<ffffffff8151dedf>] compat_do_readv_writev+0x5df/0x6e0 fs/read_write.c:984
 [<ffffffff8151e0b9>] compat_readv+0xd9/0x140 fs/read_write.c:1013
 [<ffffffff81520448>] C_SYSC_readv fs/read_write.c:1033 [inline]
 [<ffffffff81520448>] compat_SyS_readv+0xd8/0x1b0 fs/read_write.c:1022
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff837754d7>] sysenter_flags_fixed+0xd/0x17
3 locks held by syz-executor7/5687:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff81f5e9ab>] tty_ldisc_ref_wait+0x2b/0xc0 drivers/tty/tty_ldisc.c:264
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81f58d10>] n_tty_read+0x210/0x1cd0 drivers/tty/n_tty.c:2180
 #2:  (&o_tty->termios_rwsem/1){++++..}, at: [<ffffffff81f58d33>] n_tty_read+0x233/0x1cd0 drivers/tty/n_tty.c:2184
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 486 Comm: khungtaskd Not tainted 4.4.107-g610c835 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bacd5f00 task.stack: ffff8800bac88000
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c32e7>]  [<ffffffff810c32e7>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bac8fcb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000
RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300
RBP: ffff8800bac8fce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426abe0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f40c031e4e8 CR3: 00000000b6fa0000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426abe0 ffffffff847e8600 00000000000194a0 0000000000000040
 dffffc0000000000 ffff8800bac8fd00 ffffffff810b8e1b ffffffff839f53e0
 0000000000000003 ffff8800bac8fd60 ffffffff81d0f4d7 ffffffff81417c73
Call Trace:
 [<ffffffff810b8e1b>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d0f4d7>] nmi_trigger_all_cpu_backtrace+0x4a7/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b8eb4>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff81365a7a>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff81365a7a>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81365a7a>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81365a7a>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff8118dea8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff837740ef>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:468
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 3b 09 17 00 4c 89 e7 57 9d 0f 1f 
NMI backtrace for cpu 1
CPU: 1 PID: 5670 Comm: syz-executor7 Not tainted 4.4.107-g610c835 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800b6ab5f00 task.stack: ffff8801d3de8000
RIP: 0010:[<ffffffff81f51497>]  [<ffffffff81f51497>] inq_canon drivers/tty/n_tty.c:2474 [inline]
RIP: 0010:[<ffffffff81f51497>]  [<ffffffff81f51497>] n_tty_ioctl+0x207/0x2d0 drivers/tty/n_tty.c:2497
RSP: 0018:ffff8801d3def940  EFLAGS: 00000297
RAX: 0000000000010000 RBX: ffffc900050b0060 RCX: ffffffff81f514fa
RDX: 0000000000010000 RSI: ffffc90001da9000 RDI: ffffc900050b1268
RBP: ffff8801d3def980 R08: 0000000000000001 R09: ffffffff850eaab0
R10: 0000000000000001 R11: 1ffff1003a7bdeee R12: ffffc900050af000
R13: 000000071763f397 R14: 0000000020fe9000 R15: ffff8800b6419338
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f6fd4b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007f9b9d7519b8 CR3: 00000001d8656000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffffffffffff 0000000000000396 0000000000000000 ffff8800b6419100
 1ffff1003a7bdf36 000000000000541b ffffffffffffffe7 ffff8801d4db6c00
 ffff8801d3defb78 ffffffff81f487f9 ffffffff00000000 ffffffff81f51290
Call Trace:
 [<ffffffff81f487f9>] tty_ioctl+0x739/0x2100 drivers/tty/tty_io.c:2980
 [<ffffffff815589ba>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815589ba>] do_vfs_ioctl+0x7aa/0xee0 fs/ioctl.c:607
 [<ffffffff8161d98e>] C_SYSC_ioctl fs/compat_ioctl.c:1614 [inline]
 [<ffffffff8161d98e>] compat_SyS_ioctl+0x64e/0x2540 fs/compat_ioctl.c:1544
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff837754d7>] sysenter_flags_fixed+0xd/0x17
Code: 8b ac 24 68 22 00 00 31 db 4c 39 6d d0 0f 84 17 ff ff ff e8 ac c6 40 ff 48 8b 45 d0 49 8d 9c 24 60 10 00 00 4c 29 e8 48 89 45 c0 <e8> 94 c6 40 ff 4c 89 e8 25 ff 0f 00 00 48 0f a3 03 19 d2 85 d2