From 01f96c0a9922cd9919baf9d16febdf7016177a12 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 21 Sep 2011 15:30:20 +1000 Subject: md: Avoid waking up a thread after it has been freed. Two related problems: 1/ some error paths call "md_unregister_thread(mddev->thread)" without subsequently clearing ->thread. A subsequent call to mddev_unlock will try to wake the thread, and crash. 2/ Most calls to md_wakeup_thread are protected against the thread disappeared either by: - holding the ->mutex - having an active request, so something else must be keeping the array active. However mddev_unlock calls md_wakeup_thread after dropping the mutex and without any certainty of an active request, so the ->thread could theoretically disappear. So we need a spinlock to provide some protections. So change md_unregister_thread to take a pointer to the thread pointer, and ensure that it always does the required locking, and clears the pointer properly. Reported-by: "Moshe Melnikov" Signed-off-by: NeilBrown cc: stable@kernel.org --- drivers/md/multipath.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'drivers/md/multipath.c') diff --git a/drivers/md/multipath.c b/drivers/md/multipath.c index 3535c23af288..d5b5fb300171 100644 --- a/drivers/md/multipath.c +++ b/drivers/md/multipath.c @@ -514,8 +514,7 @@ static int multipath_stop (mddev_t *mddev) { multipath_conf_t *conf = mddev->private; - md_unregister_thread(mddev->thread); - mddev->thread = NULL; + md_unregister_thread(&mddev->thread); blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/ mempool_destroy(conf->pool); kfree(conf->multipaths); -- cgit v1.2.3