INFO: task syz-executor084:3865 blocked for more than 120 seconds.
      Not tainted 4.9.109-g7cecc75 #2
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor084 D28504  3865   3862 0x00000000
 ffff8801d8051800 ffff8801b57d7480 ffff8801b57d7480 ffff8801d8054800
 ffff8801db321c18 ffff8801d7e879c8 ffffffff839e8a3d ffff8801d80520c8
 ffffed003b00a418 ffff8801d8051800 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea03f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839ea9c3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839eee46>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839eee46>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
 [<ffffffff81e57a26>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81e57a26>] blkdev_ioctl+0x7b6/0x1a70 block/ioctl.c:590
 [<ffffffff81632b8e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815b2b9c>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b2b9c>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b2b9c>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b3c1f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b3c1f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9913>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/518:
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8136662c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81425cb7>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3776:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7ae2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff8211fce2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor084/3865:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3867:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3869:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3870:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3871:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3872:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3873:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3874:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3875:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3876:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3877:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3878:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3879:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3880:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3881:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by syz-executor084/3882:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825ca87b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344

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

NMI backtrace for cpu 1
CPU: 1 PID: 518 Comm: khungtaskd Not tainted 4.9.109-g7cecc75 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d90cfd08 ffffffff81eb3e29 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b9580 ffff8801d90cfd40
 ffffffff81ebf127 0000000000000001 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf127>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf0ba>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b9684>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81366bc4>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81366bc4>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81366bc4>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81366bc4>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9adc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3864 Comm: syz-executor084 Not tainted 4.9.109-g7cecc75 #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d8b2e000 task.stack: ffff8801d7d08000
RIP: 0010:[<ffffffff815b1019>] 
c [<ffffffff815b1019>] kill_fasync+0x2d9/0x410 fs/fcntl.c:738
RSP: 0018:ffff8801d7d0fbd0  EFLAGS: 00000282
RAX: ffff8801d8b2e000 RBX: ffff8801bea64280 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815b1014 RDI: ffff8801bea64378
RBP: ffff8801d7d0fbf0 R08: ffff8801d8b2e910 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000012
R13: 0000000000000000 R14: 0000000000020001 R15: ffff8801da1e6160
FS:  00000000015f9880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1f5509f000 CR3: 00000001da210000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000012
c 0000000000000000
c 0000000000000012
c ffff8801da1e6160
c
 ffff8801d7d0fc78
c ffffffff8158d7cd
c eb1c9147dd4084c2
c ffff8801d7d0fd80
c
 0000000000000012
c ffff8801bea64354
c 0000000000000001
c ffff8801d7d0fd70
c
Call Trace:
 [<ffffffff8158d7cd>] pipe_write+0x97d/0xd60 fs/pipe.c:482
 [<ffffffff8156eb60>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff8156eb60>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
 [<ffffffff81572957>] vfs_write+0x187/0x530 fs/read_write.c:557
 [<ffffffff81576789>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff81576789>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9913>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c