From: Yu Kuai <yukuai3@huawei.com>

Our test reports a uaf for 'mddev->sync_thread':

T1                      T2
md_start_sync
 md_register_thread
			raid1d
			 md_check_recovery
			  md_reap_sync_thread
			   md_unregister_thread
			    kfree

 md_wakeup_thread
  wake_up
  ->sync_thread was freed

Currently, a global spinlock 'pers_lock' is borrowed to protect
'mddev->thread', this problem can be fixed likewise, however, there might
be similar problem for other md_thread, and I really don't like the idea to
borrow a global lock.

This patchset do some refactor, and then use a disk level spinlock to
protect md_thread in relevant apis.

Yu Kuai (5):
  md: pass a md_thread pointer to md_register_thread()
  md: refactor md_wakeup_thread()
  md: use md_thread api to wake up sync_thread
  md: pass a mddev to md_unregister_thread()
  md: protect md_thread with a new disk level spin lock

 drivers/md/dm-raid.c      |   6 +-
 drivers/md/md-bitmap.c    |   6 +-
 drivers/md/md-cluster.c   |  39 +++++-----
 drivers/md/md-multipath.c |   8 +-
 drivers/md/md.c           | 157 ++++++++++++++++++++------------------
 drivers/md/md.h           |  15 ++--
 drivers/md/raid1.c        |  19 +++--
 drivers/md/raid10.c       |  31 ++++----
 drivers/md/raid5-cache.c  |  19 +++--
 drivers/md/raid5-ppl.c    |   2 +-
 drivers/md/raid5.c        |  48 ++++++------
 11 files changed, 175 insertions(+), 175 deletions(-)

-- 
2.31.1

On Sat, Mar 11, 2023 at 1:32 AM Yu Kuai <yukuai1@huaweicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@huawei.com>
>
> Our test reports a uaf for 'mddev->sync_thread':
>
> T1                      T2
> md_start_sync
>  md_register_thread
>                         raid1d
>                          md_check_recovery
>                           md_reap_sync_thread
>                            md_unregister_thread
>                             kfree
>
>  md_wakeup_thread
>   wake_up
>   ->sync_thread was freed
>
> Currently, a global spinlock 'pers_lock' is borrowed to protect
> 'mddev->thread', this problem can be fixed likewise, however, there might
> be similar problem for other md_thread, and I really don't like the idea to
> borrow a global lock.
>
> This patchset do some refactor, and then use a disk level spinlock to
> protect md_thread in relevant apis.
>
> Yu Kuai (5):
>   md: pass a md_thread pointer to md_register_thread()
>   md: refactor md_wakeup_thread()
>   md: use md_thread api to wake up sync_thread
>   md: pass a mddev to md_unregister_thread()
>   md: protect md_thread with a new disk level spin lock

Applied to md-next.

Thanks,
Song