INFO: task syz-executor.5:2125 blocked for more than 140 seconds. Not tainted 4.9.170+ #48 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D25752 2125 2120 0x00000000 ffff8801cf4c8000 ffff8801ceaf2c00 ffff8801db621000 ffff8801d1f297c0 ffff8801db621018 ffff8801a99efa28 ffffffff82801a4e ffffffff82e2bb68 ffffffff81208040 009f46cc34df5da2 ffff8801db6218f0 1ffff1003533df34 Call Trace: [<00000000b12ec025>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000fb3d9853>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<000000002d1f6ec9>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<000000002d1f6ec9>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000d549565d>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 [<000000008ad22ce9>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<000000008ad22ce9>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<0000000089dc35fd>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<00000000fb88a8af>] vfs_ioctl fs/ioctl.c:43 [inline] [<00000000fb88a8af>] file_ioctl fs/ioctl.c:493 [inline] [<00000000fb88a8af>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<0000000057f03871>] SYSC_ioctl fs/ioctl.c:694 [inline] [<0000000057f03871>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<000000003279be8d>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<000000007b431a9d>] 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: [<00000000fd0fba71>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000fd0fba71>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<0000000088ba2494>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2038: #0: (&tty->ldisc_sem){++++++}, at: [<0000000058205cc2>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000de6a3c67>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.5/2125: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000d549565d>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by syz-executor.0/2126: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000075514bbf>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000820affd5>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.3/2128: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000075514bbf>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000820affd5>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.4/2135: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000075514bbf>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000820affd5>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by syz-executor.1/3707: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000d549565d>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<000000008d4446b4>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 3 locks held by syz-executor.2/3669: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000002898e562>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d62ba517>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000001d2394d0>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<000000001d2394d0>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 1 lock held by blkid/3703: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000d549565d>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/3704: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000d549565d>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/3706: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000d549565d>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/3708: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000075514bbf>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by blkid/3710: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000075514bbf>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000820affd5>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.170+ #48 ffff8801d98d7cc8 ffffffff81b4fb21 0000000000000001 0000000000000000 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5adbc 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<0000000038d65fb3>] __dump_stack lib/dump_stack.c:15 [inline] [<0000000038d65fb3>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<0000000052ed45f1>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000002c3bc83e>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000008a784336>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000004d9581af>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000004d9581af>] check_hung_task kernel/hung_task.c:126 [inline] [<000000004d9581af>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<000000004d9581af>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000fb2b6042>] kthread+0x278/0x310 kernel/kthread.c:211 [<000000002bc3d9c1>] 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 0xffffffff82810ac2