INFO: task syz-executor.1:2092 blocked for more than 140 seconds. Not tainted 4.9.203-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D24648 2092 1 0x00000004 0000000000000083 ffff8801d26eaf80 ffff8801d1e66880 ffff8801db71ffc0 ffff8801d1b30000 ffff8801db71ffd8 ffff8801a6e5f688 ffffffff8280a79e ffff8801d26eaf80 ffffffff841f6b00 00ff8801a6e5f5e8 ffff8801db7208b0 Call Trace: [<000000006a5e2d61>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000d178b49f>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000bcfdb459>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000bcfdb459>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000359ee5fe>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 [<00000000e7f58785>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<0000000038356a59>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<0000000091dce485>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<0000000038ee66f3>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<000000003d277677>] vfs_open+0x105/0x230 fs/open.c:904 [<000000002ece54f5>] do_last fs/namei.c:3457 [inline] [<000000002ece54f5>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<00000000e1a0228f>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<000000005481a6cb>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<000000001255ba80>] SYSC_open fs/open.c:1115 [inline] [<000000001255ba80>] SyS_open+0x2d/0x40 fs/open.c:1110 [<00000000e0e69aae>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<00000000ae8185be>] 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: [<00000000a169414b>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000a169414b>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<000000001699141c>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2022: #0: (&tty->ldisc_sem){++++++}, at: [<00000000b226d6ac>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000ffb04ed5>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.1/2092: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c6e3e92d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000359ee5fe>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.2/2096: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c6e3e92d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000359ee5fe>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.5/2103: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c6e3e92d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000359ee5fe>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.4/2106: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c6e3e92d>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000359ee5fe>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.3/3926: #0: (loop_index_mutex){+.+.+.}, at: [<000000005eb5deac>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 #1: (&lo->lo_ctl_mutex#2){+.+...}, at: [<000000004e29818a>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988 2 locks held by syz-executor.0/3932: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<00000000e8e25deb>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000f49d500e>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by blkid/3938: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000008e3eaacc>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<0000000063565698>] lo_release+0x20/0x1b0 drivers/block/loop.c:1664 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.203-syzkaller #0 ffff8801d98d7cc8 ffffffff81b55f6b 0000000000000001 0000000000000000 0000000000000001 ffffffff8109a001 dffffc0000000000 ffff8801d98d7d00 ffffffff81b6120c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<00000000fe40b90b>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000fe40b90b>] dump_stack+0xcb/0x130 lib/dump_stack.c:56 [<00000000c08c466b>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000003b8c522f>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000008dd2ed10>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<0000000077125e89>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<0000000077125e89>] check_hung_task kernel/hung_task.c:126 [inline] [<0000000077125e89>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<0000000077125e89>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000b6436803>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000f990b50b>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff828198f1