INFO: task syz-executor.5:28149 blocked for more than 140 seconds. Not tainted 4.9.194+ #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D25544 28149 1 0x00000004 0000000000000083 ffff8801d7aa2f80 ffff8801a70c2100 ffff8801db621000 ffff8801ac2faf80 ffff8801db621018 ffff8801aa537b18 ffffffff8281af8e 000000000000016a 0000000000000000 00ff8801d7aa2f80 ffff8801db6218f0 Call Trace: [<000000009658cb7a>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<0000000004c83024>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000ff59dea1>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000ff59dea1>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<00000000445bc412>] lo_release+0x20/0x1b0 drivers/block/loop.c:1663 [<00000000ffbea5a1>] __blkdev_put+0x461/0x840 fs/block_dev.c:1606 [<00000000d5011ddd>] blkdev_put+0x88/0x560 fs/block_dev.c:1671 [<0000000050e8d887>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678 [<000000000cd03947>] __fput+0x274/0x720 fs/file_table.c:208 [<0000000013883644>] ____fput+0x16/0x20 fs/file_table.c:244 [<00000000c120d7b1>] task_work_run+0x108/0x180 kernel/task_work.c:116 [<0000000014490a77>] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [<0000000014490a77>] exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:163 [<000000004f449cfe>] prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] [<000000004f449cfe>] syscall_return_slowpath arch/x86/entry/common.c:266 [inline] [<000000004f449cfe>] do_syscall_64+0x3ab/0x5c0 arch/x86/entry/common.c:293 [<00000000863fc22b>] 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: [<00000000f9eefc47>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000f9eefc47>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<00000000e2263602>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 2 locks held by getty/2025: #0: (&tty->ldisc_sem){++++++}, at: [<00000000cbdc9bfd>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<00000000e8e2d983>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.5/28149: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004bd98b33>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000445bc412>] lo_release+0x20/0x1b0 drivers/block/loop.c:1663 2 locks held by syz-executor.3/8013: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<0000000043ee20c5>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000f8f53e4e>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.3/8025: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c1d041b1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 2 locks held by syz-executor.4/8017: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<0000000043ee20c5>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000f8f53e4e>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 1 lock held by syz-executor.4/8029: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c1d041b1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 1 lock held by blkid/8020: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000004d86329f>] blkdev_put+0x2b/0x560 fs/block_dev.c:1629 2 locks held by syz-executor.0/8027: #0: (loop_index_mutex){+.+.+.}, at: [<000000008ea51050>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<000000000835f237>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1987 1 lock held by syz-executor.0/8045: #0: (loop_index_mutex){+.+.+.}, at: [<000000008ea51050>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 1 lock held by syz-executor.0/8059: #0: (loop_index_mutex){+.+.+.}, at: [<000000008ea51050>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 2 locks held by blkid/8033: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c1d041b1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000053a6f860>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by blkid/8034: #0: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c1d041b1>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<0000000053a6f860>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.194+ #0 ffff8801d98d7cc8 ffffffff81b67001 0000000000000001 0000000000000000 0000000000000001 ffffffff81099d01 dffffc0000000000 ffff8801d98d7d00 ffffffff81b7229c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<0000000094a49356>] __dump_stack lib/dump_stack.c:15 [inline] [<0000000094a49356>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<000000001da35ead>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000aa38182c>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000ea18141b>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<0000000000b3a33b>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<0000000000b3a33b>] check_hung_task kernel/hung_task.c:126 [inline] [<0000000000b3a33b>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<0000000000b3a33b>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000d9173264>] kthread+0x278/0x310 kernel/kthread.c:211 [<0000000016fe7a64>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff8282a0e1