INFO: task syz-executor.4:14251 blocked for more than 140 seconds. Not tainted 4.9.205-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D25544 14251 1 0x00000004 0000000000000083 ffff8801a9d05f00 ffff88015d7f3180 ffff8801db61ffc0 ffff880061af0000 ffff8801db61ffd8 ffff8801a7cb7688 ffffffff8280a6ae 0000000041b58ab3 ffffffff82e2ad80 00ffffff81205320 ffff8801db6208b0 Call Trace: [<00000000db25b25d>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000b146d889>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000374b10a6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000374b10a6>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<0000000070f1c3f3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 [<00000000b15f3697>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<000000002fee7744>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<000000002a584e3c>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<000000006dcadd91>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<00000000ecbc6421>] vfs_open+0x105/0x230 fs/open.c:904 [<00000000a19a1a74>] do_last fs/namei.c:3457 [inline] [<00000000a19a1a74>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<0000000071af642b>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<000000005c8f87cc>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<00000000e952cc94>] SYSC_open fs/open.c:1115 [inline] [<00000000e952cc94>] SyS_open+0x2d/0x40 fs/open.c:1110 [<0000000004d11b5b>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<0000000056eca3b4>] 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: [<0000000002f8e16a>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<0000000002f8e16a>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<000000003d2e4c50>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1910: #0: (&f->f_pos_lock){+.+.+.}, at: [<000000009be105de>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2038: #0: (&tty->ldisc_sem){++++++}, at: [<00000000a5e78786>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000bbbc5a69>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.4/14251: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000003a62554e>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000070f1c3f3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.5/1848: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000003a62554e>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000070f1c3f3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.3/8277: #0: (loop_index_mutex){+.+.+.}, at: [<000000008ac12e6b>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<0000000099e3067e>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988 1 lock held by syz-executor.3/8289: #0: (loop_index_mutex){+.+.+.}, at: [<000000008ac12e6b>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 1 lock held by syz-executor.3/8301: #0: (loop_index_mutex){+.+.+.}, at: [<000000008ac12e6b>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 2 locks held by syz-executor.0/8280: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<00000000bd08b376>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000003982f6e5>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.0/8303: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000003a62554e>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/8282: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000003a62554e>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000070f1c3f3>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.205-syzkaller #0 ffff8801d98d7cc8 ffffffff81b55e6b 0000000000000001 0000000000000000 0000000000000001 ffffffff8109a001 dffffc0000000000 ffff8801d98d7d00 ffffffff81b6110c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<0000000057a823e9>] __dump_stack lib/dump_stack.c:15 [inline] [<0000000057a823e9>] dump_stack+0xcb/0x130 lib/dump_stack.c:56 [<000000001dba06fe>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<0000000007f3699f>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000966a68b0>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000a39180ae>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000a39180ae>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000a39180ae>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000a39180ae>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<0000000006d1bb93>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000fb5b0852>] 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 0xffffffff82819801