syzbot

INFO: task syz-executor.5:1425 blocked for more than 140 seconds.
      Not tainted 4.9.185+ #8
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5  D26632  1425   2094 0x00000004
 0000000000000083 ffff8801a83f4740 ffff8801a2d38580 ffff8801db621000
 ffff8801d5de97c0 ffff8801db621018 ffff8801a5d5fb18 ffffffff8280c5ae
 0000000000000168 0000000000000000 00ff8801a83f4740 ffff8801db6218f0
Call Trace:
 [<00000000cc67fd6e>] schedule+0x92/0x1c0 /kernel/sched/core.c:3546
 [<00000000e36dcaca>] schedule_preempt_disabled+0x13/0x20 /kernel/sched/core.c:3579
 [<00000000c19d8dbd>] __mutex_lock_common /kernel/locking/mutex.c:582 [inline]
 [<00000000c19d8dbd>] mutex_lock_nested+0x38d/0x920 /kernel/locking/mutex.c:621
 [<000000003b8e6ff4>] lo_release+0x20/0x1b0 /drivers/block/loop.c:1663
 [<000000002034cca5>] __blkdev_put+0x461/0x840 /fs/block_dev.c:1606
 [<000000009d94f3af>] blkdev_put+0x88/0x560 /fs/block_dev.c:1671
 [<0000000063879b66>] blkdev_close+0x8b/0xb0 /fs/block_dev.c:1678
 [<00000000e9f378c7>] __fput+0x274/0x720 /fs/file_table.c:208
 [<000000009999e9a1>] ____fput+0x16/0x20 /fs/file_table.c:244
 [<000000008c59d4a5>] task_work_run+0x108/0x180 /kernel/task_work.c:116
 [<00000000728c4faa>] tracehook_notify_resume /./include/linux/tracehook.h:191 [inline]
 [<00000000728c4faa>] exit_to_usermode_loop+0x13b/0x160 /arch/x86/entry/common.c:163
 [<00000000518133d5>] prepare_exit_to_usermode /arch/x86/entry/common.c:195 [inline]
 [<00000000518133d5>] syscall_return_slowpath /arch/x86/entry/common.c:266 [inline]
 [<00000000518133d5>] do_syscall_64+0x3ab/0x5c0 /arch/x86/entry/common.c:293
 [<0000000009e05aae>] 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: [<00000000167aa574>] check_hung_uninterruptible_tasks /kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<00000000167aa574>] watchdog+0x14b/0xaf0 /kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<00000000769f8bb4>] debug_show_all_locks+0x7f/0x21f /kernel/locking/lockdep.c:4336
2 locks held by getty/2025:
 #0:  (&tty->ldisc_sem){++++++}, at: [<0000000092efbca5>] ldsem_down_read+0x33/0x40 /drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<000000001bd6eb80>] n_tty_read+0x1fe/0x1820 /drivers/tty/n_tty.c:2156
2 locks held by syz-executor.5/1425:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000009eb301d2>] __blkdev_put+0xbb/0x840 /fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<000000003b8e6ff4>] lo_release+0x20/0x1b0 /drivers/block/loop.c:1663
1 lock held by blkid/1424:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000d79ab370>] blkdev_put+0x2b/0x560 /fs/block_dev.c:1629
1 lock held by syz-executor.4/1428:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000d79ab370>] blkdev_put+0x2b/0x560 /fs/block_dev.c:1629
2 locks held by blkid/1429:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<000000009eb301d2>] __blkdev_put+0xbb/0x840 /fs/block_dev.c:1587
 #1:  (loop_index_mutex){+.+.+.}, at: [<000000003b8e6ff4>] lo_release+0x20/0x1b0 /drivers/block/loop.c:1663
2 locks held by syz-executor.3/1437:
 #0:  (loop_index_mutex){+.+.+.}, at: [<000000008e34421a>] loop_control_ioctl+0x7a/0x320 /drivers/block/loop.c:1973
 #1:  (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<0000000028bd3d8c>] loop_control_ioctl+0x17f/0x320 /drivers/block/loop.c:1987
2 locks held by syz-executor.0/1435:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<00000000d76c5815>] lo_ioctl+0x8e/0x1b10 /drivers/block/loop.c:1404
 #1:  (&bdev->bd_mutex){+.+.+.}, at: [<00000000ac3b5da5>] blkdev_reread_part+0x1f/0x40 /block/ioctl.c:189
2 locks held by syz-executor.2/1443:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000095abcd99>] __blkdev_get+0x10e/0xeb0 /fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<000000002b2e6fc4>] lo_open+0x1d/0xb0 /drivers/block/loop.c:1621
2 locks held by blkid/1436:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000095abcd99>] __blkdev_get+0x10e/0xeb0 /fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<000000002b2e6fc4>] lo_open+0x1d/0xb0 /drivers/block/loop.c:1621
1 lock held by syz-executor.1/1442:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000095abcd99>] __blkdev_get+0x10e/0xeb0 /fs/block_dev.c:1273
2 locks held by blkid/1441:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<0000000095abcd99>] __blkdev_get+0x10e/0xeb0 /fs/block_dev.c:1273
 #1:  (loop_index_mutex){+.+.+.}, at: [<000000002b2e6fc4>] lo_open+0x1d/0xb0 /drivers/block/loop.c:1621

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.185+ #8
 ffff8801d98efcc8 ffffffff81b5a081 0000000000000001 0000000000000000
 0000000000000001 ffffffff81099a01 dffffc0000000000 ffff8801d98efd00
 ffffffff81b6531c 0000000000000001 0000000000000000 0000000000000001
Call Trace:
 [<00000000914e94ee>] __dump_stack /lib/dump_stack.c:15 [inline]
 [<00000000914e94ee>] dump_stack+0xc1/0x120 /lib/dump_stack.c:51
 [<000000000f730c39>] nmi_cpu_backtrace.cold+0x47/0x87 /lib/nmi_backtrace.c:99
 [<0000000036a55850>] nmi_trigger_cpumask_backtrace+0x124/0x155 /lib/nmi_backtrace.c:60
 [<00000000995af52c>] arch_trigger_cpumask_backtrace+0x14/0x20 /arch/x86/kernel/apic/hw_nmi.c:37
 [<000000005b9258fe>] trigger_all_cpu_backtrace /./include/linux/nmi.h:58 [inline]
 [<000000005b9258fe>] check_hung_task /kernel/hung_task.c:126 [inline]
 [<000000005b9258fe>] check_hung_uninterruptible_tasks /kernel/hung_task.c:183 [inline]
 [<000000005b9258fe>] watchdog+0x670/0xaf0 /kernel/hung_task.c:263
 [<00000000baa6cec7>] kthread+0x278/0x310 /kernel/kthread.c:211
 [<00000000508d6766>] 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 0xffffffff8281b701