INFO: task syz-executor.2:2115 blocked for more than 140 seconds. Not tainted 4.9.168+ #39 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D25528 2115 1 0x00000004 ffff8801d190c740 ffff8801d3b32680 ffff8801db621000 ffff8801d3a74740 ffff8801db621018 ffff8801a97d7988 ffffffff8280028e 0000000000000000 ffffffff830c1d40 00ff8801a97d79b0 ffff8801db6218f0 1ffff100352faf20 Call Trace: [<0000000045da031d>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<000000005b7a315c>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000d6cb6a3d>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000d6cb6a3d>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000006d644f10>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 [<00000000e692a90a>] loop_reread_partitions+0x7c/0x90 drivers/block/loop.c:638 [<00000000f1921422>] loop_clr_fd+0x7dd/0xa60 drivers/block/loop.c:1082 [<00000000b9274909>] lo_ioctl+0x7b6/0x1a10 drivers/block/loop.c:1415 [<000000000fab6293>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<000000000fab6293>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<00000000768d3d0f>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<000000003812f912>] vfs_ioctl fs/ioctl.c:43 [inline] [<000000003812f912>] file_ioctl fs/ioctl.c:493 [inline] [<000000003812f912>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<00000000956a868e>] SYSC_ioctl fs/ioctl.c:694 [inline] [<00000000956a868e>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<00000000bfa5a893>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<00000000ae726f2b>] 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: [<0000000033f48011>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [<0000000033f48011>] watchdog+0x13c/0xae0 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [<00000000ba381050>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1896: #0: (&f->f_pos_lock){+.+.+.}, at: [<000000005c6b4223>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2023: #0: (&tty->ldisc_sem){++++++}, at: [<000000008f12c93f>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<00000000d6f479f2>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.2/2115: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000049b48e00>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000006d644f10>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 3 locks held by syz-executor.3/2116: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000098f64127>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000b8918dde>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000001158ef6f>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000001158ef6f>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by syz-executor.1/2120: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000008bb5d589>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000004ee3fda5>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by syz-executor.4/2124: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000049b48e00>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/19083: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000049b48e00>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.5/19091: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<0000000049b48e00>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/19093: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000008bb5d589>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/19094: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000008bb5d589>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000004ee3fda5>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.168+ #39 ffff8801d98d7cc8 ffffffff81b4f5d1 0000000000000000 0000000000000000 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5a86c 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<000000006b81a254>] __dump_stack lib/dump_stack.c:15 [inline] [<000000006b81a254>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<000000002599f73a>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000b9caa860>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000008894a80c>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000e93047a1>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000e93047a1>] check_hung_task kernel/hung_task.c:125 [inline] [<00000000e93047a1>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [<00000000e93047a1>] watchdog+0x661/0xae0 kernel/hung_task.c:239 [<00000000dbe7fbda>] kthread+0x278/0x310 kernel/kthread.c:211 [<000000001477eaac>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff8280f302