INFO: task syz-executor068:2438 blocked for more than 140 seconds. Not tainted 4.9.194+ #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor068 D29096 2438 2435 0x00000000 0000000000000083 ffff8801c80d97c0 ffff8801c858ac00 ffff8801db721000 ffff8801c9775f00 ffff8801db721018 ffff8801c81d7688 ffffffff8281af8e ffff8801c80d97c0 ffffffff841f8b40 00ff8801c81d75e8 ffff8801db7218f0 Call Trace: [<000000000f0a2ed7>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000f5acc27b>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000924350c3>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000924350c3>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000001859d03e>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 [<00000000b249d5d9>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<0000000021ddb2ff>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<00000000f7133286>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<000000005c73c70a>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<00000000fcb80e78>] vfs_open+0x105/0x230 fs/open.c:904 [<000000002356d63d>] do_last fs/namei.c:3541 [inline] [<000000002356d63d>] path_openat+0xbf5/0x2f60 fs/namei.c:3665 [<000000003cf8e71c>] do_filp_open+0x1a1/0x280 fs/namei.c:3699 [<00000000535f7b1a>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<00000000563f4a14>] SYSC_open fs/open.c:1115 [inline] [<00000000563f4a14>] SyS_open+0x2d/0x40 fs/open.c:1110 [<0000000043927aeb>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<000000004d3265b6>] 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: [<000000003c48beb4>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<000000003c48beb4>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<000000006c930669>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 1 lock held by rsyslogd/1897: #0: (&f->f_pos_lock){+.+.+.}, at: [<00000000c430600a>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2025: #0: (&tty->ldisc_sem){++++++}, at: [<00000000e099ab48>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000201a1b54>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor068/2438: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e6504f3f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001859d03e>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 1 lock held by syz-executor068/2469: #0: (loop_index_mutex){+.+.+.}, at: [<000000005cca9fb3>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 2 locks held by syz-executor068/2472: #0: (loop_index_mutex){+.+.+.}, at: [<000000005cca9fb3>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<000000005304b2bd>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1987 2 locks held by syz-executor068/2473: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000006ee9fa0d>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d48edcc7>] lo_release+0x20/0x1b0 drivers/block/loop.c:1663 1 lock held by blkid/2475: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c9323e6a>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 2 locks held by blkid/2476: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000006ee9fa0d>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d48edcc7>] lo_release+0x20/0x1b0 drivers/block/loop.c:1663 2 locks held by syz-executor068/2480: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e6504f3f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001859d03e>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 1 lock held by blkid/2482: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e6504f3f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 1 lock held by blkid/2483: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e6504f3f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/2484: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e6504f3f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001859d03e>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor068/2485: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<00000000bfaf2b37>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000006b0b5cf4>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by blkid/2487: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000e6504f3f>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001859d03e>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.194+ #0 ffff8801d98d7cc8 ffffffff81b67001 0000000000000001 0000000000000000 0000000000000001 ffffffff81099d01 dffffc0000000000 ffff8801d98d7d00 ffffffff81b7229c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<000000006dae6b7e>] __dump_stack lib/dump_stack.c:15 [inline] [<000000006dae6b7e>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000cd495e85>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<0000000024dda49f>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000039273c7>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000007597b42d>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000007597b42d>] check_hung_task kernel/hung_task.c:126 [inline] [<000000007597b42d>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<000000007597b42d>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000ef32b2f2>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000840713bf>] 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 0xffffffff8282a0e1