INFO: task syz-executor.3:14982 blocked for more than 140 seconds. Not tainted 4.9.171+ #49 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D25592 14982 1 0x00000004 ffff8801c5fb8000 0000000000000000 ffff8801db621000 ffffffff83031180 ffff8801db621018 ffff8801d2fbf598 ffffffff82801dde ffffffff82e2bc18 ffffffff812080d0 00ffffff83c806d0 ffff8801db6218f0 1ffff1003a5f7ea2 Call Trace: [<00000000db6b7f33>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<000000005c1ab07b>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000508a3e5c>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000508a3e5c>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000007f359d0f>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 [<0000000003f83b7d>] fuse_lookup+0x89/0x3b0 fs/fuse/dir.c:406 [<000000006387abc7>] lookup_slow+0x24b/0x480 fs/namei.c:1709 [<000000000c061ac1>] walk_component+0x71e/0xce0 fs/namei.c:1825 [<00000000d139193a>] link_path_walk+0x897/0x1200 fs/namei.c:2161 [<00000000d6f82e9f>] path_mountpoint+0x67/0x6d0 fs/namei.c:2737 [<0000000030ff3934>] filename_mountpoint+0x17f/0x350 fs/namei.c:2758 [<00000000d06b4ef9>] user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2788 [<00000000450311fe>] SYSC_umount fs/namespace.c:1722 [inline] [<00000000450311fe>] SyS_umount+0x136/0xd30 fs/namespace.c:1706 [<0000000075fd4e35>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<00000000cd05d3fc>] 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: [<00000000490a6d57>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000490a6d57>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<0000000092cc31b9>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 2 locks held by getty/2034: #0: (&tty->ldisc_sem){++++++}, at: [<00000000600f1187>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<000000006a8d75b1>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.3/14982: #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000a9955f87>] inode_lock_shared include/linux/fs.h:778 [inline] #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000a9955f87>] lookup_slow+0x160/0x480 fs/namei.c:1686 #1: (&fi->mutex){+.+.+.}, at: [<000000007f359d0f>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 2 locks held by syz-executor.3/15888: #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000a9955f87>] inode_lock_shared include/linux/fs.h:778 [inline] #0: (&type->i_mutex_dir_key#7){++++++}, at: [<00000000a9955f87>] lookup_slow+0x160/0x480 fs/namei.c:1686 #1: (&fi->mutex){+.+.+.}, at: [<000000007f359d0f>] fuse_lock_inode+0xad/0xe0 fs/fuse/inode.c:364 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.171+ #49 ffff8801d98d7cc8 ffffffff81b4fb61 0000000000000000 0000000000000000 0000000000000000 ffffffff81097501 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5adfc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<0000000006a9b830>] __dump_stack lib/dump_stack.c:15 [inline] [<0000000006a9b830>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000c71f987a>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000002da64967>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000f9f78132>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<0000000039f8fc4c>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<0000000039f8fc4c>] check_hung_task kernel/hung_task.c:126 [inline] [<0000000039f8fc4c>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<0000000039f8fc4c>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<0000000052d39fe4>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000e715d7ba>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 16219 Comm: init Not tainted 4.9.171+ #49 task: 000000000de1d57c task.stack: 00000000907d5742 RIP: 0010:[] c [<00000000100a7536>] io_serial_in+0x6b/0x90 drivers/tty/serial/8250/8250_port.c:414 RSP: 0018:ffff8801d4b67570 EFLAGS: 00000002 RAX: dffffc0000000000 RBX: 00000000000003fd RCX: 0000000000000000 RDX: 00000000000003fd RSI: ffffffff81d6f621 RDI: ffffffff84b63b58 RBP: ffff8801d4b67580 R08: ffffffff84064ac0 R09: ffffffff82a550a0 R10: ffffffff83c74b80 R11: 0000000000000001 R12: ffffffff84b63b20 R13: 0000000000000020 R14: fffffbfff096c7ab R15: fffffbfff096c76d FS: 00007f53c9ff37a0(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f53c9706a30 CR3: 0000000186f90000 CR4: 00000000001606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff84b63b20c 000000000000270cc ffff8801d4b675d0c ffffffff81d718c4c ffff8801d4b67608c ffffffff84b63b68c ffffffff84b63d5ac ffffffff841d2383c ffffffff84b63b20c 0000000000000032c dffffc0000000000c 0000000000000032c Call Trace: [<00000000705a9a4c>] serial_in drivers/tty/serial/8250/8250.h:111 [inline] [<00000000705a9a4c>] wait_for_xmitr+0x94/0x1e0 drivers/tty/serial/8250/8250_port.c:1997 [<000000009e4fddf9>] serial8250_console_putchar+0x20/0x60 drivers/tty/serial/8250/8250_port.c:3103 [<000000008a82e212>] uart_console_write+0x56/0xe0 drivers/tty/serial/serial_core.c:1886 [<0000000090e83d9b>] serial8250_console_write+0x2fb/0x860 drivers/tty/serial/8250/8250_port.c:3169 [<000000002359c87e>] univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:594 [<000000008621e2de>] call_console_drivers.isra.0.constprop.0+0x1ac/0x360 kernel/printk/printk.c:1594 [<000000003d9db6f1>] console_unlock+0x47c/0xb20 kernel/printk/printk.c:2454 [<0000000035eb0af3>] console_device+0x97/0xc0 kernel/printk/printk.c:2562 [<00000000846f97f1>] tty_lookup_driver drivers/tty/tty_io.c:2018 [inline] [<00000000846f97f1>] tty_open_by_driver drivers/tty/tty_io.c:2063 [inline] [<00000000846f97f1>] tty_open+0x796/0xe10 drivers/tty/tty_io.c:2140 [<0000000010a787cc>] chrdev_open+0x230/0x630 fs/char_dev.c:392 [<000000004783edd0>] do_dentry_open+0x422/0xd20 fs/open.c:772 [<00000000e8f23a3c>] vfs_open+0x105/0x230 fs/open.c:885 [<00000000ef0abcf7>] do_last fs/namei.c:3457 [inline] [<00000000ef0abcf7>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<00000000834e0e0e>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<00000000a9ab66a9>] do_sys_open+0x2f0/0x610 fs/open.c:1078 [<0000000002dd16ee>] SYSC_open fs/open.c:1096 [inline] [<0000000002dd16ee>] SyS_open+0x2d/0x40 fs/open.c:1091 [<0000000075fd4e35>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<00000000cd05d3fc>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Code: c24 cc9 c00 c00 c00 c49 c8d c7c c24 c38 c48 cb8 c00 c00 c00 c00 c00 cfc cff cdf c48 c89 cfa c48 cc1 cea c03 cd3 ce3 c80 c3c c02 c00 c75 c17 c41 c03 c5c c24 c38 c89 cda cec c<5b> c0f cb6 cc0 c41 c5c c5d cc3 ce8 c58 c97 c78 cff ceb cc2 ce8 cb1 c97 c78 cff ceb c