[PATCH v2 0/5] md: fix uaf for sync_thread

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

Changes in v2:
 - fix a compile error for for md-cluster in patch 2
 - replace spin_lock/unlock with spin_lock/unlock_irq in patch 5
 - don't wake up inside the new lock in md wakeup_thread in patch 5

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.

I tested this pathset with mdadm tests, and there are no new regression,
by the way, following test will failed with or without this patchset:

01raid6integ
04r1update
05r6tor0
10ddf-create
10ddf-fail-spare
10ddf-fail-stop-readd
10ddf-geometry

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           | 162 ++++++++++++++++++++------------------
 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, 177 insertions(+), 178 deletions(-)

-- 
2.31.1