INFO: task syz-executor.2:20594 blocked for more than 140 seconds.
      Not tainted 4.9.203-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2  D27640 20594   7865 0x00000004
 0000000000000087 ffff8801c88017c0 ffff8801d2d57380 ffff8801db61ffc0
 ffff8801d282c740 ffff8801db61ffd8 ffff8801d81dfb68 ffffffff8280a79e
 0000000000000000 0000000000000000 0000000000000066 ffff8801db6208b0
Call Trace:
 [<000000000f9e3e87>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<00000000ce13671b>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<00000000f466cc73>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<00000000f466cc73>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
 [<000000000d3e76cd>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<000000000d3e76cd>] file_ioctl fs/ioctl.c:493 [inline]
 [<000000000d3e76cd>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677
 [<000000000dbe7302>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<000000000dbe7302>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<000000004c07173b>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<00000000d6c83cdb>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<00000000924c5382>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<00000000924c5382>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<0000000022f7e9fc>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339
2 locks held by getty/2030:
 #0:  (&tty->ldisc_sem){++++++}, at: [<000000007dfaf31c>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<00000000f0b6801c>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.2/20594:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
1 lock held by syz-executor.4/20596:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
2 locks held by syz-executor.4/20606:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
 #1:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<00000000e69d2ec6>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988
1 lock held by syz-executor.5/20598:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
2 locks held by syz-executor.0/20599:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<0000000010b154c7>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<000000001bb52bc9>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
1 lock held by syz-executor.0/20607:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
1 lock held by syz-executor.0/20620:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
1 lock held by syz-executor.0/20636:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000792a2f36>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
1 lock held by syz-executor.0/20637:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000286a0d7>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
2 locks held by blkid/20615:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000792a2f36>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<000000001eeb17e2>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622

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

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.203-syzkaller #0
 ffff8801d98d7cc8 ffffffff81b55f6b 0000000000000001 0000000000000000
 0000000000000001 ffffffff8109a001 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b6120c 0000000000000001 0000000000000000 0000000000000001
Call Trace:
 [<0000000096ad74c7>] __dump_stack lib/dump_stack.c:15 [inline]
 [<0000000096ad74c7>] dump_stack+0xcb/0x130 lib/dump_stack.c:56
 [<000000001b98e90b>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<000000006e5e631b>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<00000000b4ddc38f>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<00000000affb5bbc>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<00000000affb5bbc>] check_hung_task kernel/hung_task.c:126 [inline]
 [<00000000affb5bbc>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<00000000affb5bbc>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<00000000d4bf4945>] kthread+0x278/0x310 kernel/kthread.c:211
 [<000000004a21930b>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff828198f1