diff options
| author | Jens Axboe <jaxboe@fusionio.com> | 2011-06-05 06:01:13 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-07-08 23:15:23 -0700 |
| commit | b1ad9117b692986f2fc0d2d1b3f6f56b696d38cc (patch) | |
| tree | 70453c1d7f7cf67072acf497fede0fe7b58ad59d | |
| parent | 11c30d19fccd0f63f447b20588b84c1deb059745 (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.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index ab7a9e6a9b1..d31adc2c951 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2704,8 +2704,11 @@ static void __cfq_exit_single_io_context(struct cfq_data *cfqd, smp_wmb(); cic->key = cfqd_dead_key(cfqd); - 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]); |