INFO: task syz-executor.1:5341 blocked for more than 140 seconds.
      Not tainted 4.9.184+ #5
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1  D25544  5341      1 0x00000004
 0000000000000087 ffff8801c9dbaf80 ffff8801cfd9e300 ffff8801db721000
 ffff8801cfdc97c0 ffff8801db721018 ffff8801ccab7598 ffffffff8280a5ce
 ffffffff82e2e020 ffffffff8120b8c0 00ffffff83c82a40 ffff8801db7218f0
Call Trace:
 [<00000000cea06abd>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<0000000035e4d706>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579
 [<00000000a3301c17>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<00000000a3301c17>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621
 [<00000000f3d664c6>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364
 [<00000000ffc05149>] fuse_lookup+0x89/0x3b0 fs/fuse/dir.c:406
 [<0000000055b59ebb>] lookup_slow+0x24b/0x480 fs/namei.c:1709
 [<000000002afdf2b6>] walk_component+0x71e/0xce0 fs/namei.c:1825
 [<0000000033735ecc>] link_path_walk+0x897/0x1200 fs/namei.c:2161
 [<00000000b7bd0081>] path_mountpoint+0x67/0x6d0 fs/namei.c:2737
 [<0000000098d3308a>] filename_mountpoint+0x17f/0x350 fs/namei.c:2758
 [<00000000bf72fa76>] user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2788
 [<000000009df852a8>] SYSC_umount fs/namespace.c:1722 [inline]
 [<000000009df852a8>] SyS_umount+0x136/0xd30 fs/namespace.c:1706
 [<000000006c209850>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<00000000bca3704f>] 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: [<00000000cfdfe9fd>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<00000000cfdfe9fd>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<00000000f701a97f>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
2 locks held by rs:main Q:Reg/1892:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<00000000ea8d3750>] __fdget_pos+0xa8/0xd0 fs/file.c:782
 #1:  (sb_writers#4){.+.+.+}, at: [<00000000c1db723f>] file_start_write include/linux/fs.h:2646 [inline]
 #1:  (sb_writers#4){.+.+.+}, at: [<00000000c1db723f>] vfs_write+0x3e9/0x520 fs/read_write.c:558
2 locks held by getty/2022:
 #0:  (&tty->ldisc_sem){++++++}, at: [<00000000813c196a>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<000000004b780521>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.1/5341:
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<0000000095bb605d>] inode_lock_shared include/linux/fs.h:781 [inline]
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<0000000095bb605d>] lookup_slow+0x160/0x480 fs/namei.c:1686
 #1:  (&fi->mutex){+.+.+.}, at: [<00000000f3d664c6>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364
2 locks held by syz-executor.1/12055:
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<0000000095bb605d>] inode_lock_shared include/linux/fs.h:781 [inline]
 #0:  (&type->i_mutex_dir_key#7){++++++}, at: [<0000000095bb605d>] lookup_slow+0x160/0x480 fs/namei.c:1686
 #1:  (&fi->mutex){+.+.+.}, at: [<00000000f3d664c6>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.184+ #5
 ffff8801d98d7cc8 ffffffff81b580a1 0000000000000000 0000000000000000
 0000000000000000 ffffffff81099a01 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b6333c 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<00000000314be661>] __dump_stack lib/dump_stack.c:15 [inline]
 [<00000000314be661>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<00000000c72d8eec>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<00000000389ca78a>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<00000000807e2c25>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<000000005bcb35d7>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<000000005bcb35d7>] check_hung_task kernel/hung_task.c:126 [inline]
 [<000000005bcb35d7>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<000000005bcb35d7>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<00000000776f42f5>] kthread+0x278/0x310 kernel/kthread.c:211
 [<0000000098f1facb>] 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 0xffffffff82819721