INFO: task syz-executor.4:2120 blocked for more than 140 seconds. Not tainted 4.9.171+ #49 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D25528 2120 1 0x00000004 ffff8801cedf17c0 ffff8801d5deac00 ffff8801db621000 ffff8801cb6417c0 ffff8801db621018 ffff8801a8557a28 ffffffff82801dde ffffffff82e2bc18 ffffffff812080d0 001c11e99182bab9 ffff8801db6218f0 1ffff100350aaf34 Call Trace: [<000000004705b759>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<0000000096be02dc>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000cb261142>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000cb261142>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000a965dec3>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 [<000000003845ed83>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<000000003845ed83>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<000000007ace9da2>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<00000000251bd42f>] vfs_ioctl fs/ioctl.c:43 [inline] [<00000000251bd42f>] file_ioctl fs/ioctl.c:493 [inline] [<00000000251bd42f>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<00000000420a205c>] SYSC_ioctl fs/ioctl.c:694 [inline] [<00000000420a205c>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<00000000072d48e8>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<00000000fa5c5729>] 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: [<000000002b044e3f>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<000000002b044e3f>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<000000006fd7ba7a>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 1 lock held by rsyslogd/1900: #0: (&f->f_pos_lock){+.+.+.}, at: [<00000000fcc2e693>] __fdget_pos+0xa8/0xd0 fs/file.c:782 2 locks held by getty/2027: #0: (&tty->ldisc_sem){++++++}, at: [<00000000ad1948e7>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<000000009fa7812c>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.4/2120: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a965dec3>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by syz-executor.0/2118: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000039eb6b91>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 1 lock held by syz-executor.3/2121: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a965dec3>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by syz-executor.2/2124: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000039eb6b91>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000047218e54>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.1/2129: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000039eb6b91>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000047218e54>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.5/4367: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a965dec3>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<0000000018d8b92b>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 3 locks held by blkid/4363: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000239655e7>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000a6edd1f9>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<0000000002d837e3>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<0000000002d837e3>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 1 lock held by blkid/4375: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000a965dec3>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/4379: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000039eb6b91>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/4381: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000039eb6b91>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000047218e54>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.171+ #49 ffff8801d98d7cc8 ffffffff81b4fb61 0000000000000000 0000000000000000 0000000000000000 ffffffff81097501 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5adfc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<00000000a979fb36>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000a979fb36>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000e57b2f39>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000ec94a976>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000697965e1>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000d19dcfef>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000d19dcfef>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000d19dcfef>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000d19dcfef>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<000000007910b651>] kthread+0x278/0x310 kernel/kthread.c:211 [<000000001ab58733>] 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 0xffffffff82810e52