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authorJens Axboe <jaxboe@fusionio.com>2011-06-05 06:01:13 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-07-13 05:31:24 +0200
commitd234df5a1ed1bab59b88660548c30ff1af69de5b (patch)
tree6b1947f49bec834655f0a0ee43a36cd07c7e2675
parentb115036a750c9bba4b9a598683eb5105744fe196 (diff)
cfq-iosched: fix locking around ioc->ioc_data assignment
commit ab4bd22d3cce6977dc039664cc2d052e3147d662 upstream. Since we are modifying this RCU pointer, we need to hold the lock protecting it around it. This fixes a potential reuse and double free of a cfq io_context structure. The bug has been in CFQ for a long time, it hit very few people but those it did hit seemed to see it a lot. Tracked in RH bugzilla here: https://bugzilla.redhat.com/show_bug.cgi?id=577968 Credit goes to Paul Bolle for figuring out that the issue was around the one-hit ioc->ioc_data cache. Thanks to his hard work the issue is now fixed. Signed-off-by: Jens Axboe <jaxboe@fusionio.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--block/cfq-iosched.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index abc5d8087b0c..6b481a6af9d8 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2537,8 +2537,11 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
cic->dead_key = (unsigned long) cic->key;
cic->key = NULL;
- if (ioc->ioc_data == cic)
+ if (rcu_dereference(ioc->ioc_data) == cic) {
+ spin_lock(&ioc->lock);
rcu_assign_pointer(ioc->ioc_data, NULL);
+ spin_unlock(&ioc->lock);
+ }
if (cic->cfqq[BLK_RW_ASYNC]) {
cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);