INFO: task syz-executor.4:2140 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.4 D25424 2140 1 0x10000004 ffff8801cf0817c0 ffff8801d9ea8000 ffff8801db621000 ffff8801a2db0000 ffff8801db621018 ffff8801a5c47b28 ffffffff82801a4e ffffffff82e30b9f ffff8801a5c47aa0 00ffffff81bb61ac ffff8801db6218f0 1ffff10034b88f54 Call Trace: [<000000009b07bf0c>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000809072e3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<0000000049730970>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<0000000049730970>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<0000000089c14b9c>] __lo_release drivers/block/loop.c:1642 [inline] [<0000000089c14b9c>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 [<00000000a40266ca>] __blkdev_put+0x461/0x840 fs/block_dev.c:1606 [<00000000ac0e6830>] blkdev_put+0x88/0x560 fs/block_dev.c:1671 [<0000000058512569>] blkdev_close+0x8b/0xb0 fs/block_dev.c:1678 [<000000000e88b7cc>] __fput+0x274/0x720 fs/file_table.c:208 [<00000000c37553ab>] ____fput+0x16/0x20 fs/file_table.c:244 [<0000000038bf24f3>] task_work_run+0x108/0x180 kernel/task_work.c:116 [<00000000e2f109f4>] tracehook_notify_resume include/linux/tracehook.h:191 [inline] [<00000000e2f109f4>] exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:162 [<00000000760f8d79>] prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline] [<00000000760f8d79>] syscall_return_slowpath arch/x86/entry/common.c:263 [inline] [<00000000760f8d79>] do_syscall_64+0x3f7/0x570 arch/x86/entry/common.c:290 [<000000007e4f46b2>] 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: [<00000000a3d72d4b>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000a3d72d4b>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.?..}, at: [<00000000179e6eb4>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4339 2 locks held by getty/2021: #0: (&tty->ldisc_sem){++++++}, at: [<000000007fe981ad>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [<0000000010688bea>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 3 locks held by syz-executor.4/2140: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000008218e510>] __blkdev_put+0xbb/0x840 fs/block_dev.c:1587 #1: (loop_index_mutex){+.+.+.}, at: [<00000000c089ebb4>] lo_release+0x1e/0x1b0 drivers/block/loop.c:1664 #2: (loop_ctl_mutex#2){+.+.+.}, at: [<0000000089c14b9c>] __lo_release drivers/block/loop.c:1642 [inline] #2: (loop_ctl_mutex#2){+.+.+.}, at: [<0000000089c14b9c>] lo_release+0x84/0x1b0 drivers/block/loop.c:1665 2 locks held by syz-executor.5/23716: #0: (loop_ctl_mutex/1){+.+.+.}, at: [<000000005f6f0d56>] lo_ioctl+0x85/0x1a10 drivers/block/loop.c:1405 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000bb1433aa>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by syz-executor.2/15848: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000020d5380a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000000fcfe93f>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 2 locks held by blkid/21990: #0: (&bdev->bd_mutex){+.+.+.}, at: [<0000000020d5380a>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000000fcfe93f>] lo_open+0x1d/0xb0 drivers/block/loop.c:1622 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.170+ #48 ffff8801d98d7cc8 ffffffff81b4fb21 0000000000000000 0000000000000000 0000000000000000 ffffffff81097401 dffffc0000000000 ffff8801d98d7d00 ffffffff81b5adbc 0000000000000000 0000000000000000 0000000000000000 Call Trace: [<000000009254b623>] __dump_stack lib/dump_stack.c:15 [inline] [<000000009254b623>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000adb2169c>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000d20da8bc>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<00000000098dc46c>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<0000000006571ff2>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<0000000006571ff2>] check_hung_task kernel/hung_task.c:126 [inline] [<0000000006571ff2>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<0000000006571ff2>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<0000000080af5907>] kthread+0x278/0x310 kernel/kthread.c:211 [<00000000edda13e5>] 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 CPU: 1 PID: 29706 Comm: syz-executor.1 Not tainted 4.9.170+ #48 task: 00000000a6813401 task.stack: 00000000174d7835 RIP: 0033:[<0000000000401584>] c [<0000000042bf52a8>] 0x401584 RSP: 002b:00007f1b943d7690 EFLAGS: 00000282 RAX: 0000000099888397 RBX: 000000000000000b RCX: 0000000000458da9 RDX: 258b0d9a00a41a08 RSI: 00007f1b943d76c0 RDI: 000000000000000b RBP: 0000000000000000 R08: 5c649dec23c3d2f3 R09: 0000000000000000 R10: 100000043d4f1713 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 00007f1b943d8700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000007121b4 CR3: 00000001caccc000 CR4: 00000000001606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600