INFO: task syz-executor.0:2114 blocked for more than 140 seconds. Not tainted 4.9.188+ #19 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D25016 2114 1 0x00000004 0000000000000087 ffff8801cf6897c0 ffff8801cf4ef900 ffff8801db721000 ffff8801ce8fc740 ffff8801db721018 ffff8801aa427598 ffffffff8281749e ffffffff81bcb25c ffff8801aa4275c8 00ffffff8120416e ffff8801db7218f0 Call Trace: [<000000006c858ace>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000d6ea96bc>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000cce34dbf>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000cce34dbf>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<0000000094f6ba40>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 [<0000000041ed6206>] fuse_lookup+0x89/0x3b0 fs/fuse/dir.c:406 [<0000000026fc00ee>] lookup_slow+0x24b/0x480 fs/namei.c:1709 [<0000000077030e6e>] walk_component+0x71e/0xce0 fs/namei.c:1825 [<00000000697328f3>] link_path_walk+0x8b4/0x1210 fs/namei.c:2161 [<000000003079db7d>] path_mountpoint+0x67/0x6d0 fs/namei.c:2737 [<00000000b7f792ee>] filename_mountpoint+0x17f/0x350 fs/namei.c:2758 [<00000000e5f6f0fd>] user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2788 [<000000008af30614>] SYSC_umount fs/namespace.c:1722 [inline] [<000000008af30614>] SyS_umount+0x136/0xd30 fs/namespace.c:1706 [<00000000b1fa3be8>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<00000000b32a1231>] 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: [<00000000767d750f>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000767d750f>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000fe2008da>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 1 lock held by rsyslogd/1898: #0: (&f->f_pos_lock){+.+.+.}, at: [<00000000f32f48da>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2026: #0: (&tty->ldisc_sem){++++++}, at: [<00000000b224d26c>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000d34a0f39>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.0/2114: #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000af8b94ff>] inode_lock_shared include/linux/fs.h:781 [inline] #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000af8b94ff>] lookup_slow+0x160/0x480 fs/namei.c:1686 #1: (&fi->mutex){+.+.+.}, at: [<0000000094f6ba40>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 2 locks held by syz-executor.0/18931: #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000af8b94ff>] inode_lock_shared include/linux/fs.h:781 [inline] #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000af8b94ff>] lookup_slow+0x160/0x480 fs/namei.c:1686 #1: (&fi->mutex){+.+.+.}, at: [<0000000094f6ba40>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.188+ #19 ffff8801d98d7cc8 ffffffff81b64a21 0000000000000000 0000000000000000 0000000000000000 ffffffff81099a01 dffffc0000000000 ffff8801d98d7d00 ffffffff81b6fcbc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<00000000bd43c900>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000bd43c900>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<000000006277cbcf>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000c975b8e3>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000006e9e2034>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000fbce8b16>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000fbce8b16>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000fbce8b16>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000fbce8b16>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000c7fc4c0c>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000cc2d8a7c>] 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 0xffffffff828265f1