INFO: task syz-executor.4:14752 blocked for more than 140 seconds. Not tainted 4.9.202+ #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D25544 14752 1 0x00000004 0000000000000083 ffff88019fbc8000 0000000000000000 ffff8801db61ffc0 ffff8801d635af80 ffff8801db61ffd8 ffff8801d6aff688 ffffffff8280a1de ffffffff81bbc38c ffffffff82e2ad88 000000000002a8e8 ffff8801db6208b0 Call Trace: [<0000000018f9b351>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000311b9ad2>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<000000005093fa6e>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<000000005093fa6e>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<0000000017ede969>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 [<0000000038ee9226>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<00000000985576be>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<000000007739c2e4>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<00000000162f0d3f>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<000000000add26b5>] vfs_open+0x105/0x230 fs/open.c:904 [<00000000f302af52>] do_last fs/namei.c:3457 [inline] [<00000000f302af52>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<00000000441b99ed>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<00000000c30ac8d0>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<0000000044327a56>] SYSC_open fs/open.c:1115 [inline] [<0000000044327a56>] SyS_open+0x2d/0x40 fs/open.c:1110 [<00000000a1104350>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<00000000a8f8972f>] 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: [<00000000d3ad7013>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000d3ad7013>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000cfc18cf2>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by rs:main Q:Reg/1911: #0: (&f->f_pos_lock){+.+.+.}, at: [<000000006462b880>] __fdget_pos+0xa8/0xd0 fs/file.c:782 #1: (sb_writers#4){.+.+.+}, at: [<00000000cc19bbb6>] file_start_write include/linux/fs.h:2645 [inline] #1: (sb_writers#4){.+.+.+}, at: [<00000000cc19bbb6>] vfs_write+0x3e9/0x520 fs/read_write.c:558 1 lock held by rsyslogd/1913: #0: (&f->f_pos_lock){+.+.+.}, at: [<000000006462b880>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2042: #0: (&tty->ldisc_sem){++++++}, at: [<00000000d1d1e785>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<0000000004434cc3>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.4/14752: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e7fd4612>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000017ede969>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.5/15854: #0: (loop_index_mutex){+.+.+.}, at: [<000000004d0c0058>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<00000000009d7188>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988 1 lock held by syz-executor.5/15861: #0: (loop_index_mutex){+.+.+.}, at: [<000000004d0c0058>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 1 lock held by syz-executor.5/15901: #0: (loop_index_mutex){+.+.+.}, at: [<000000004d0c0058>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 1 lock held by syz-executor.5/15904: #0: (loop_index_mutex){+.+.+.}, at: [<000000004d0c0058>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 2 locks held by syz-executor.0/15855: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<0000000063d23082>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d5f58cb6>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.0/15858: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e7fd4612>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/15857: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e7fd4612>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000017ede969>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.202+ #0 ffff8801d9907cc8 ffffffff81b55d2b 0000000000000000 0000000000000000 0000000000000000 ffffffff8109a001 dffffc0000000000 ffff8801d9907d00 ffffffff81b60fcc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<00000000c0b23bd2>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000c0b23bd2>] dump_stack+0xcb/0x130 lib/dump_stack.c:56 [<00000000d0dac26a>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000c38295a8>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<0000000011dae46c>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000cfbe23a0>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000cfbe23a0>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000cfbe23a0>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000cfbe23a0>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<0000000099eb83a4>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000d72b20f8>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff82819331