Re: INFO: task hung in blkdev_reread_part

[Dmitry Vyukov]

On Sat, Dec 9, 2017 at 11:43 AM, syzbot
<bot+7ca1333efc3e4a9174c86149436ecea8053ec13c@xxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> a0651c7fa2c088a605f63792279859608ed7f2c8
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
>
> Unfortunately, I don't have any reproducer for this bug yet.
>
>
> netlink: 16 bytes leftover after parsing attributes in process
> `syz-executor1'.
> INFO: task syz-executor4:9515 blocked for more than 120 seconds.
>       Not tainted 4.15.0-rc1+ #204
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> syz-executor4   D20544  9515   3350 0x00000004
> Call Trace:
>  context_switch kernel/sched/core.c:2799 [inline]
>  __schedule+0x8eb/0x2060 kernel/sched/core.c:3375
>  schedule+0xf5/0x430 kernel/sched/core.c:3434
>  schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3492
>  __mutex_lock_common kernel/locking/mutex.c:833 [inline]
>  __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893
>  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>  blkdev_reread_part+0x1e/0x40 block/ioctl.c:192
>  loop_reread_partitions+0x12f/0x1a0 drivers/block/loop.c:619
>  loop_set_status+0x9ba/0xf60 drivers/block/loop.c:1161
>  loop_set_status64+0x95/0x100 drivers/block/loop.c:1271
>  lo_ioctl+0xd98/0x1b90 drivers/block/loop.c:1381
>  __blkdev_driver_ioctl block/ioctl.c:303 [inline]
>  blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601
>  block_ioctl+0xea/0x130 fs/block_dev.c:1860
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>  SYSC_ioctl fs/ioctl.c:701 [inline]
>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>  entry_SYSCALL_64_fastpath+0x1f/0x96
> RIP: 0033:0x4529d9
> RSP: 002b:00007f09e88bbc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 00000000004529d9
> RDX: 0000000020a8ff18 RSI: 0000000000004c04 RDI: 0000000000000016
> RBP: 0000000000000540 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f4ea0
> R13: 00000000ffffffff R14: 00007f09e88bc6d4 R15: 0000000000000000
>
> Showing all locks held in the system:
> 2 locks held by khungtaskd/674:
>  #0:  (rcu_read_lock){....}, at: [<00000000396cd1a8>]
> check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
>  #0:  (rcu_read_lock){....}, at: [<00000000396cd1a8>] watchdog+0x1c5/0xd60
> kernel/hung_task.c:249
>  #1:  (tasklist_lock){.+.+}, at: [<0000000096a7b7f4>]
> debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554
> 2 locks held by getty/3054:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000c828faca>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a7f4335e>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3055:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000c828faca>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a7f4335e>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3056:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000c828faca>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a7f4335e>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3057:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000c828faca>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a7f4335e>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3058:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000c828faca>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a7f4335e>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3059:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000c828faca>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a7f4335e>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by getty/3060:
>  #0:  (&tty->ldisc_sem){++++}, at: [<00000000c828faca>]
> ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
>  #1:  (&ldata->atomic_read_lock){+.+.}, at: [<00000000a7f4335e>]
> n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131
> 2 locks held by syz-executor4/9515:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e7502bc1>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
>  #1:  (&bdev->bd_mutex){+.+.}, at: [<00000000435b4ba4>]
> blkdev_reread_part+0x1e/0x40 block/ioctl.c:192
> 1 lock held by syz-executor4/9522:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e7502bc1>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
> 1 lock held by syz-executor4/9541:
>  #0:  (&bdev->bd_mutex){+.+.}, at: [<00000000b174d747>]
> __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439
> 1 lock held by syz-executor7/9521:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e7502bc1>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
> 1 lock held by syz-executor7/9525:
>  #0:  (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000e7502bc1>]
> lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355
> 1 lock held by syz-executor7/9547:
>  #0:  (&bdev->bd_mutex){+.+.}, at: [<00000000b174d747>]
> __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439
> 2 locks held by blkid/9520:
>  #0:  (&bdev->bd_mutex){+.+.}, at: [<00000000b174d747>]
> __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439
>  #1:  (loop_index_mutex){+.+.}, at: [<000000005253b538>] lo_open+0x1b/0xa0
> drivers/block/loop.c:1571
> 1 lock held by syz-executor0/9527:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor0/9554:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 2 locks held by syz-executor5/9526:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
>  #1:  (&lo->lo_ctl_mutex#2){+.+.}, at: [<000000001a5f807e>]
> loop_control_ioctl+0x1a7/0x490 drivers/block/loop.c:1946
> 1 lock held by syz-executor5/9542:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor2/9530:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor2/9564:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor6/9534:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor6/9556:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor3/9539:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor3/9565:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor1/9543:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
> 1 lock held by syz-executor1/9566:
>  #0:  (loop_index_mutex){+.+.}, at: [<00000000268a88d7>]
> loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932
>
> =============================================
>
> NMI backtrace for cpu 0
> CPU: 0 PID: 674 Comm: khungtaskd Not tainted 4.15.0-rc1+ #204
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
>  nmi_trigger_cpumask_backtrace+0x122/0x180 lib/nmi_backtrace.c:62
>  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
>  trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
>  check_hung_task kernel/hung_task.c:132 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
>  watchdog+0x90c/0xd60 kernel/hung_task.c:249
>  kthread+0x37a/0x440 kernel/kthread.c:238
>  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10
> arch/x86/include/asm/irqflags.h:54

+loop maintainers

#syz dup: INFO: task hung in lo_ioctl

> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
> Please credit me with: Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
>
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