INFO: task syz-executor2:31660 blocked for more than 120 seconds.
      Not tainted 4.9.105-gd7e64f8 #43
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor2   D29072 31660   3879 0x20020004
 ffff88019615b000 ffff8801b55939c0 ffff8801be1cea00 ffff8801a5dbc800
 ffff8801db321c18 ffff8801d6167be8 ffffffff839e8c1d ffff88019615b8c8
 ffffed0032c2b718 ffff88019615b000 00fffc0000000000 ffff8801db3224e8
Call Trace:
 [<ffffffff839ea21f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff839eaba3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff839ef026>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff839ef026>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff825cc662>] lo_compat_ioctl+0xe2/0x140 drivers/block/loop.c:1528
 [<ffffffff81ea5955>] compat_blkdev_ioctl+0x3a5/0x3ad0 block/compat_ioctl.c:751
 [<ffffffff8168ee46>] C_SYSC_ioctl fs/compat_ioctl.c:1602 [inline]
 [<ffffffff8168ee46>] compat_SyS_ioctl+0x126/0x1fe0 fs/compat_ioctl.c:1549
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff839fb210>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

Showing all locks held in the system:
2 locks held by khungtaskd/520:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81366b9c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81366b9c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81426180>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/3783:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7cc2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82120062>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor2/31660:
 #0:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<ffffffff825cc662>] lo_compat_ioctl+0xe2/0x140 drivers/block/loop.c:1528
1 lock held by syz-executor2/31661:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825cab6b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by blkid/31653:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825cab6b>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344

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

NMI backtrace for cpu 0
CPU: 0 PID: 520 Comm: khungtaskd Not tainted 4.9.105-gd7e64f8 #43
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d95afd08 ffffffff81eb41a9 0000000000000000 0000000000000000
 0000000000000000 0000000000000001 ffffffff810b96a0 ffff8801d95afd40
 ffffffff81ebf4a7 0000000000000000 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb41a9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb41a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf4a7>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf43a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b97a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81367134>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81367134>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81367134>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81367134>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9cdc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 31652 Comm: syz-executor2 Not tainted 4.9.105-gd7e64f8 #43
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d78be000 task.stack: ffff8801cda60000
RIP: 0010:[<ffffffff8135eeeb>] 
c [<ffffffff8135eeeb>] __read_once_size include/linux/compiler.h:243 [inline]
RIP: 0010:[<ffffffff8135eeeb>] 
c [<ffffffff8135eeeb>] __sanitizer_cov_trace_pc+0x3b/0x50 kernel/kcov.c:105
RSP: 0018:ffff8801cda67c98  EFLAGS: 00000246
RAX: 0000000000040000 RBX: ffff8801cbffc690 RCX: ffffc9000293e000
RDX: 000000000003ffff RSI: ffffffff825cc06b RDI: ffff88018eb933b0
RBP: ffff8801cda67c98 R08: ffff8801d78be910 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff1003af17d1d R12: ffff8801cbffc690
R13: ffff8801d5d92280 R14: ffff8801d3823600 R15: ffff8801d3823758
FS:  0000000000000000(0000) GS:ffff8801db300000(0063) knlGS:00000000f5722b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 0000000001d79000 CR3: 00000001d6db1000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8801cda67d20
c ffffffff825cc06b
c ffff8801cda67ca8
c ffff8801cda67ca8
c
 ffff8801d3823750
c 0000000000006000
c ffff8801d3a301d0
c ffff8801cbffc888
c
 ffff8801cda40e00
c ffff8801d5d92360
c ffff88010002001d
c ffff880100000000
c
Call Trace:
 [<ffffffff825cc06b>] is_loop_device drivers/block/loop.c:704 [inline]
 [<ffffffff825cc06b>] loop_set_fd drivers/block/loop.c:886 [inline]
 [<ffffffff825cc06b>] lo_ioctl+0x158b/0x1aa0 drivers/block/loop.c:1347
 [<ffffffff825cc632>] lo_compat_ioctl+0xb2/0x140 drivers/block/loop.c:1540
 [<ffffffff81ea5955>] compat_blkdev_ioctl+0x3a5/0x3ad0 block/compat_ioctl.c:751
 [<ffffffff8168ee46>] C_SYSC_ioctl fs/compat_ioctl.c:1602 [inline]
 [<ffffffff8168ee46>] compat_SyS_ioctl+0x126/0x1fe0 fs/compat_ioctl.c:1549
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff839fb210>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137
Code: 
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c<48> 
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c48 
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cd1 
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c00 
c