INFO: task syz-executor.1:2131 blocked for more than 140 seconds. Not tainted 4.9.165+ #28 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D25016 2131 1 0x00000004 ffff8801c8194740 ffff8801d1719600 ffff8801db721000 ffff8801d1495f00 ffff8801db721018 ffff8801a691f598 ffffffff827fbd7e ffffffff81bafe1c ffffffff81207f30 00ffffff83c7e4e0 ffff8801db7218f0 1ffff10034d23ea2 Call Trace: [] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 [] fuse_lookup+0x89/0x3b0 fs/fuse/dir.c:406 [] lookup_slow+0x24b/0x480 fs/namei.c:1709 [] walk_component+0x71e/0xce0 fs/namei.c:1825 [] link_path_walk+0x897/0x1200 fs/namei.c:2161 [] path_mountpoint+0x67/0x6d0 fs/namei.c:2737 [] filename_mountpoint+0x17f/0x350 fs/namei.c:2758 [] user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2788 [] SYSC_umount fs/namespace.c:1722 [inline] [] SyS_umount+0x136/0xd30 fs/namespace.c:1706 [] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [] 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: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x13c/0xae0 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 2 locks held by getty/2028: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.1/2131: #0: (&type->i_mutex_dir_key#7){++++++}, at: [] inode_lock_shared include/linux/fs.h:778 [inline] #0: (&type->i_mutex_dir_key#7){++++++}, at: [] lookup_slow+0x160/0x480 fs/namei.c:1686 #1: (&fi->mutex){+.+.+.}, at: [] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 2 locks held by syz-executor.1/4114: #0: (&type->i_mutex_dir_key#7){++++++}, at: [] inode_lock_shared include/linux/fs.h:778 [inline] #0: (&type->i_mutex_dir_key#7){++++++}, at: [] lookup_slow+0x160/0x480 fs/namei.c:1686 #1: (&fi->mutex){+.+.+.}, at: [] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.165+ #28 ffff8801d98d7cc8 ffffffff81b4baf1 0000000000000001 0000000000000000 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b56d7c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x661/0xae0 kernel/hung_task.c:239 [] kthread+0x278/0x310 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff8280adf2