INFO: task syz-executor.3:2116 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.3 D25528 2116 1 0x00000004 ffff8801d0a317c0 ffff8801c5e3b700 ffff8801db721000 ffff8801d22adf00 ffff8801db721018 ffff8801abfe7a28 ffffffff8280028e ffff88021fffd050 ffff88021fffd048 00ff88021fffd05c ffff8801db7218f0 1ffff100357fcf34 Call Trace: [<00000000875b509d>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000dd4f0109>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<000000001985c744>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<000000001985c744>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000ca05bebb>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 [<0000000058b0093b>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<0000000058b0093b>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<00000000103806ac>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<0000000001001ebf>] vfs_ioctl fs/ioctl.c:43 [inline] [<0000000001001ebf>] file_ioctl fs/ioctl.c:493 [inline] [<0000000001001ebf>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<00000000f5001561>] SYSC_ioctl fs/ioctl.c:694 [inline] [<00000000f5001561>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<000000002cda304e>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<0000000048f0f951>] 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: [<000000006e206b6b>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [<000000006e206b6b>] watchdog+0x13c/0xae0 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [<00000000d195a730>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 1 lock held by rsyslogd/1900: #0: (&f->f_pos_lock){+.+.+.}, at: [<00000000f3a177e6>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2028: #0: (&tty->ldisc_sem){++++++}, at: [<00000000500d7018>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<000000007a5c33fe>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.3/2116: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000ca05bebb>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.0/2121: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d843edfa>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by syz-executor.2/2122: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d843edfa>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000009b82e7d9>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 3 locks held by syz-executor.4/2128: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000b37c8050>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000da8efa35>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<0000000017eab819>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<0000000017eab819>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by syz-executor.5/22000: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000ca05bebb>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000008babc81b>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.1/22005: #0: (loop_index_mutex){+.+.+.}, at: [<0000000034e55bef>] loop_control_ioctl+0x7a/0x2f0 drivers/block/loop.c:1973 2 locks held by blkid/22007: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d843edfa>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000009b82e7d9>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by blkid/22010: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d843edfa>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000009b82e7d9>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by blkid/22011: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000d843edfa>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.168+ #40 ffff8801d98d7cc8 ffffffff81b4f5d1 0000000000000001 0000000000000000 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5a86c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<00000000340c3eb2>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000340c3eb2>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000dd298347>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000e6051e58>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000d2308270>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000007bfab440>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000007bfab440>] check_hung_task kernel/hung_task.c:125 [inline] [<000000007bfab440>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [<000000007bfab440>] watchdog+0x661/0xae0 kernel/hung_task.c:239 [<00000000ca56ec30>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000e2ddc11b>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff8280f302