INFO: task syz-executor.5:12730 blocked for more than 140 seconds.
      Not tainted 4.9.205-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D25544 12730      1 0x00000004
 0000000000000083 ffff8801d3904740 0000000000000000 ffff8801db71ffc0
 ffff8801da6b2f80 ffff8801db71ffd8 ffff88019c99f688 ffffffff8280a6ae
 0000000041b58ab3 ffffffff82e2ad80 00ffffff81205320 ffff8801db7208b0
Call Trace:
 [<000000009e3e4a64>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<00000000b40bbb82>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<00000000197c4e24>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<00000000197c4e24>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<00000000a2ea717f>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
 [<000000003ac19189>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287
 [<00000000f0e1d042>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424
 [<000000005525a235>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579
 [<000000003f2a819d>] do_dentry_open+0x422/0xd20 fs/open.c:791
 [<0000000036cb81db>] vfs_open+0x105/0x230 fs/open.c:904
 [<0000000067b48bf8>] do_last fs/namei.c:3457 [inline]
 [<0000000067b48bf8>] path_openat+0xbf5/0x2f60 fs/namei.c:3581
 [<00000000104afd38>] do_filp_open+0x1a1/0x280 fs/namei.c:3615
 [<000000005354e597>] do_sys_open+0x2f0/0x610 fs/open.c:1097
 [<00000000abf3b8b6>] SYSC_open fs/open.c:1115 [inline]
 [<00000000abf3b8b6>] SyS_open+0x2d/0x40 fs/open.c:1110
 [<00000000e527572b>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<0000000018c155cb>] 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: [<000000009a9fa4d0>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<000000009a9fa4d0>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<00000000e5b37eb3>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339
1 lock held by rsyslogd/1902:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<000000000856857b>] __fdget_pos+0xa8/0xd0 fs/file.c:782
2 locks held by getty/2029:
 #0:  (&tty->ldisc_sem){++++++}, at: [<000000000623b965>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<00000000167822dc>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.5/12730:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000aad4e712>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000a2ea717f>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
2 locks held by syz-executor.4/26931:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000aad4e712>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000a2ea717f>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
2 locks held by syz-executor.1/27694:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000aad4e712>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000a2ea717f>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622
2 locks held by syz-executor.3/28124:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000000b3f7a4b>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974
 #1:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<000000009bfc8d74>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988
2 locks held by syz-executor.0/28134:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<00000000661e9c97>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<000000007a2ff82a>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189
2 locks held by blkid/28136:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000aad4e712>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<00000000a2ea717f>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.205-syzkaller #0
 ffff8801d98d7cc8 ffffffff81b55e6b 0000000000000000 0000000000000000
 0000000000000000 ffffffff8109a001 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b6110c 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<000000006acd23af>] __dump_stack lib/dump_stack.c:15 [inline]
 [<000000006acd23af>] dump_stack+0xcb/0x130 lib/dump_stack.c:56
 [<000000009f45cdac>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<000000000b308e45>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<00000000843b199a>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<00000000995a2e79>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<00000000995a2e79>] check_hung_task kernel/hung_task.c:126 [inline]
 [<00000000995a2e79>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<00000000995a2e79>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<00000000682c4cda>] kthread+0x278/0x310 kernel/kthread.c:211
 [<00000000c87b1cd6>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff82819801