INFO: task syz-executor.2:2109 blocked for more than 140 seconds. Not tainted 4.9.168+ #40 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D24760 2109 1 0x00000004 ffff8801cee62f80 ffff8801cf569600 ffff8801db721000 ffff8801d0ed2f80 ffff8801db721018 ffff8801a920fa28 ffffffff8280028e ffffffff82e2b8a0 ffffffff81207f30 009f4aa3a7ca1782 ffff8801db7218f0 1ffff10035241f34 Call Trace: [<000000009952a90d>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000205b5d17>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000f6c7f832>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000f6c7f832>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000a1bcadb4>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 [<000000003280d6cf>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<000000003280d6cf>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<00000000d6a3d120>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<00000000f199dea9>] vfs_ioctl fs/ioctl.c:43 [inline] [<00000000f199dea9>] file_ioctl fs/ioctl.c:493 [inline] [<00000000f199dea9>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<00000000f408a682>] SYSC_ioctl fs/ioctl.c:694 [inline] [<00000000f408a682>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<000000006c654e13>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<000000003b64f610>] 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: [<000000002b37b225>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [<000000002b37b225>] watchdog+0x13c/0xae0 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [<00000000ac7a3ce5>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1892: #0: (&f->f_pos_lock){+.+.+.}, at: [<0000000097c55ea3>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2020: #0: (&tty->ldisc_sem){++++++}, at: [<000000005972f830>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000f4c2c30b>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.2/2109: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a1bcadb4>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.0/2114: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d66c20d4>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 1 lock held by syz-executor.4/2116: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a1bcadb4>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.5/2122: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a1bcadb4>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by syz-executor.3/2129: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d66c20d4>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000006315a05e>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 3 locks held by blkid/4112: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004134fed5>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<000000006f1e0d15>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000009f90d947>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000009f90d947>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by syz-executor.1/4116: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a1bcadb4>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000004b2935d1>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by blkid/4117: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d66c20d4>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000006315a05e>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by blkid/4122: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d66c20d4>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000006315a05e>] 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+ #40 ffff8801d98d7cc8 ffffffff81b4f5d1 0000000000000000 0000000000000000 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5a86c 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<0000000025c9f97a>] __dump_stack lib/dump_stack.c:15 [inline] [<0000000025c9f97a>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<0000000060ae29a2>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<0000000054385bfc>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000003ebcee6c>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000f37a2863>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000f37a2863>] check_hung_task kernel/hung_task.c:125 [inline] [<00000000f37a2863>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [<00000000f37a2863>] watchdog+0x661/0xae0 kernel/hung_task.c:239 [<0000000032766529>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000526b59f1>] 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