INFO: task syz-executor.1:2115 blocked for more than 140 seconds. Not tainted 4.9.168+ #40 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D25272 2115 1 0x00000004 ffff8801d1cd8000 0000000000000000 ffff8801db621000 ffffffff83031180 ffff8801db621018 ffff8801ad85f688 ffffffff8280028e ffff8801d1cd8000 ffffffff841f18c0 00ff8801ad85f5e8 ffff8801db6218f0 1ffff10035b0bec0 Call Trace: [<000000004a04f7b8>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<0000000046a43754>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<000000005a073bba>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<000000005a073bba>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000d017b8c3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 [<00000000edadce5e>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<000000008ada6357>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<00000000168b4641>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<00000000d32ee3bc>] do_dentry_open+0x422/0xd20 fs/open.c:772 [<00000000be054912>] vfs_open+0x105/0x230 fs/open.c:885 [<000000004964cc2a>] do_last fs/namei.c:3457 [inline] [<000000004964cc2a>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<00000000f83d306d>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<00000000290453a1>] do_sys_open+0x2f0/0x610 fs/open.c:1078 [<00000000df6e2f10>] SYSC_open fs/open.c:1096 [inline] [<00000000df6e2f10>] SyS_open+0x2d/0x40 fs/open.c:1091 [<00000000731adf32>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<00000000fb989066>] 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: [<00000000be4d89f1>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [<00000000be4d89f1>] watchdog+0x13c/0xae0 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [<000000007b66bb9a>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2028: #0: (&tty->ldisc_sem){++++++}, at: [<0000000046f75f3a>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<000000002ea6811b>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.1/2115: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004d8140d3>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d017b8c3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.5/2121: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004d8140d3>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d017b8c3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.3/2122: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004d8140d3>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d017b8c3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.2/2126: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004d8140d3>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d017b8c3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.4/3197: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000082d8778a>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000364b04dc>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.4/3212: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004d8140d3>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by syz-executor.0/3206: #0: (loop_index_mutex){+.+.+.}, at: [<0000000054be0577>] loop_control_ioctl+0x7a/0x2f0 drivers/block/loop.c:1973 #1: (loop_ctl_mutex#2){+.+.+.}, at: [<00000000436304ff>] loop_control_ioctl+0x177/0x2f0 drivers/block/loop.c:1987 1 lock held by syz-executor.0/3208: #0: (loop_index_mutex){+.+.+.}, at: [<0000000054be0577>] loop_control_ioctl+0x7a/0x2f0 drivers/block/loop.c:1973 1 lock held by syz-executor.0/3210: #0: (loop_index_mutex){+.+.+.}, at: [<0000000054be0577>] loop_control_ioctl+0x7a/0x2f0 drivers/block/loop.c:1973 1 lock held by syz-executor.0/3213: #0: (loop_index_mutex){+.+.+.}, at: [<0000000054be0577>] loop_control_ioctl+0x7a/0x2f0 drivers/block/loop.c:1973 2 locks held by blkid/3207: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004d8140d3>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d017b8c3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.168+ #40 ffff8801d98d7cc8 ffffffff81b4f5d1 0000000000000001 0000000000000000 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5a86c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<00000000db9e03e3>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000db9e03e3>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000970375aa>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000bc997432>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000e8a2c097>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000006f296f32>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000006f296f32>] check_hung_task kernel/hung_task.c:125 [inline] [<000000006f296f32>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [<000000006f296f32>] watchdog+0x661/0xae0 kernel/hung_task.c:239 [<00000000b5708189>] kthread+0x278/0x310 kernel/kthread.c:211 [<0000000001c19a6f>] 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 0xffffffff8280f302