INFO: task syz-executor.4:2098 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.4 D25016 2098 1 0x00000004 0000000000000083 ffff8801d1a4df00 ffff8801d00a0000 ffff8801db61ffc0 ffff8801c57e4740 ffff8801db61ffd8 ffff8801a2a5f688 ffffffff8280a79e 0000000041b58ab3 ffffffff82e2adf8 00ffffff81205320 ffff8801db6208b0 Call Trace: [<000000006b2e091d>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<000000007d022017>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000fc9679aa>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000fc9679aa>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000573a3c05>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 [<0000000028d0e4b8>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<00000000848d7ccb>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<00000000ff00329a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<00000000e5d5bde1>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<0000000090b4d961>] vfs_open+0x105/0x230 fs/open.c:904 [<0000000047cb67ea>] do_last fs/namei.c:3457 [inline] [<0000000047cb67ea>] path_openat+0xbf5/0x2f60 fs/namei.c:3581 [<00000000938540db>] do_filp_open+0x1a1/0x280 fs/namei.c:3615 [<00000000b7e8b758>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<000000008a2bc3fa>] SYSC_open fs/open.c:1115 [inline] [<000000008a2bc3fa>] SyS_open+0x2d/0x40 fs/open.c:1110 [<000000002df1516b>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<00000000806449fd>] 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: [<000000000919114b>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<000000000919114b>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000cacee25a>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2024: #0: (&tty->ldisc_sem){++++++}, at: [<000000001ca331b8>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<00000000465ca482>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.4/2098: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000ded1316a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000573a3c05>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.5/4834: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000ded1316a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000573a3c05>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.3/9756: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000ded1316a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000573a3c05>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.2/11740: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000ded1316a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000573a3c05>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.0/12692: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<0000000033e4bc69>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000a57b76d0>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.0/12700: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000ded1316a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by syz-executor.1/12693: #0: (loop_index_mutex){+.+.+.}, at: [<000000007a8ba179>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1974 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<00000000fda4004b>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1988 2 locks held by blkid/12699: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000ded1316a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000573a3c05>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.203-syzkaller #0 ffff8801d98d7cc8 ffffffff81b55f6b 0000000000000000 0000000000000000 0000000000000000 ffffffff8109a001 dffffc0000000000 ffff8801d98d7d00 ffffffff81b6120c 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<0000000017b2ae0e>] __dump_stack lib/dump_stack.c:15 [inline] [<0000000017b2ae0e>] dump_stack+0xcb/0x130 lib/dump_stack.c:56 [<000000005680ac0e>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<0000000016621472>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000006d6ad87c>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000001628160e>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000001628160e>] check_hung_task kernel/hung_task.c:126 [inline] [<000000001628160e>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<000000001628160e>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<000000000e2159ef>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000a8e2b03b>] 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 0xffffffff828198f1