INFO: task syz-executor.1:3955 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.1 D25528 3955 1 0x00000004 0000000000000087 ffff8801a19797c0 0000000000000000 ffff8801db61ffc0 ffffffff83031180 ffff8801db61ffd8 ffff8801d27576a8 ffffffff8280a6ae 0000000000000246 ffffffff831f2ae8 00ff8801a197a068 ffff8801db6208b0 Call Trace: [<0000000039d8292b>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000bfb426b8>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000cb31db21>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000cb31db21>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000c7af7180>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 [<00000000937023e5>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<00000000927a2119>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<000000009bb4324b>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<00000000366d644f>] vfs_open+0x105/0x230 fs/open.c:904 [<000000003afa13b2>] do_last fs/namei.c:3457 [inline] [<000000003afa13b2>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<000000002c01ee6e>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<000000007d212735>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<00000000564f704f>] SYSC_open fs/open.c:1115 [inline] [<00000000564f704f>] SyS_open+0x2d/0x40 fs/open.c:1110 [<00000000ba48ab20>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<0000000027b5f91a>] 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: [<000000009d15fdf3>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<000000009d15fdf3>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<000000006313df84>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1894: #0: (&f->f_pos_lock){+.+.+.}, at: [<00000000050af662>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2021: #0: (&tty->ldisc_sem){++++++}, at: [<00000000670187c3>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<000000002ad57789>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.1/3955: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c7af7180>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by syz-executor.5/8842: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c7af7180>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000b0e704e7>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.3/10134: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c7af7180>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000b0e704e7>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.2/12814: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c7af7180>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000b0e704e7>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.0/13587: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<00000000a034ad94>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000000f80127a>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by syz-executor.4/15302: #0: (loop_index_mutex){+.+.+.}, at: [<00000000972f31e8>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<00000000102cedc0>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988 2 locks held by blkid/15339: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c7af7180>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000b0e704e7>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by blkid/15342: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c7af7180>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000b0e704e7>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.205-syzkaller #0 ffff8801d98d7cc8 ffffffff81b55e6b 0000000000000000 0000000000000000 0000000000000000 ffffffff8109a001 dffffc0000000000 ffff8801d98d7d00 ffffffff81b6110c 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<00000000a469f571>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000a469f571>] dump_stack+0xcb/0x130 lib/dump_stack.c:56 [<000000001148b23e>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000006f7b79dd>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000b40ad932>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000008d786797>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000008d786797>] check_hung_task kernel/hung_task.c:126 [inline] [<000000008d786797>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<000000008d786797>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<000000005e669d50>] kthread+0x278/0x310 kernel/kthread.c:211 [<000000002a4579bf>] 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 0xffffffff82819801