INFO: task syz-executor.4:2130 blocked for more than 140 seconds. Not tainted 4.9.170+ #45 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D25504 2130 1 0x00000004 ffff8801cea42f80 ffff8801cee51b80 ffff8801db721000 ffff8801cea397c0 ffff8801db721018 ffff8801ab7cfa28 ffffffff8280185e 0000000041b58ab3 ffffffff82e2b9b0 00ffffff81200360 ffff8801db7218f0 1ffff100356f9f34 Call Trace: [<0000000010dedb70>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000d6096b29>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000033bef2b>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000033bef2b>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000faced6a9>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 [<00000000ba8068f8>] __blkdev_driver_ioctl block/ioctl.c:294 [inline] [<00000000ba8068f8>] blkdev_ioctl+0xe14/0x19e0 block/ioctl.c:590 [<00000000b142ee65>] block_ioctl+0xde/0x120 fs/block_dev.c:1696 [<00000000d3f118f5>] vfs_ioctl fs/ioctl.c:43 [inline] [<00000000d3f118f5>] file_ioctl fs/ioctl.c:493 [inline] [<00000000d3f118f5>] do_vfs_ioctl+0xb87/0x11d0 fs/ioctl.c:677 [<000000004d457a30>] SYSC_ioctl fs/ioctl.c:694 [inline] [<000000004d457a30>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685 [<000000005f579546>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285 [<000000004dc95c72>] 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: [<000000001ada4cbc>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<000000001ada4cbc>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000506efc3f>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2039: #0: (&tty->ldisc_sem){++++++}, at: [<000000007750428f>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<00000000b1a2e45a>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 1 lock held by syz-executor.4/2130: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000faced6a9>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by syz-executor.0/2148: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bf1d8dfd>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000737aa6d9>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by syz-executor.1/2168: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000faced6a9>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by syz-executor.2/2172: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bf1d8dfd>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000737aa6d9>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 3 locks held by syz-executor.3/5466: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000009f5ae601>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000d5afea6d>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+...}, at: [<000000007adce5a6>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+...}, at: [<000000007adce5a6>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by syz-executor.5/5486: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000faced6a9>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000378489ce>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.5/5498: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bf1d8dfd>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 1 lock held by blkid/5484: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000faced6a9>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/5487: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000faced6a9>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 1 lock held by blkid/5493: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<00000000faced6a9>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 2 locks held by blkid/5495: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bf1d8dfd>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<00000000737aa6d9>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 1 lock held by blkid/5499: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bf1d8dfd>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.170+ #45 ffff8801d98d7cc8 ffffffff81b4fb21 0000000000000001 0000000000000000 0000000000000001 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5adbc 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<00000000964a7d1f>] __dump_stack lib/dump_stack.c:15 [inline] [<00000000964a7d1f>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000c8898287>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<000000004e6f7a2a>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<0000000001dc4e3f>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<00000000c2f931e1>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<00000000c2f931e1>] check_hung_task kernel/hung_task.c:126 [inline] [<00000000c2f931e1>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<00000000c2f931e1>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<0000000029d9e03d>] kthread+0x278/0x310 kernel/kthread.c:211 [<000000003332c117>] 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 0xffffffff828108d2