diff options
| author | Jens Axboe <jaxboe@fusionio.com> | 2011-06-05 06:01:13 +0200 |
|---|---|---|
| committer | Paul Gortmaker <paul.gortmaker@windriver.com> | 2012-05-17 11:21:00 -0400 |
| commit | 470564b1d4c27fd2bafc421acf49718bfcf5ea5a (patch) | |
| tree | a035f12836e0bfd8f97d450577cdaba1383ca182 /block | |
| parent | b24a9d3db0f8d01f6c6088b2026f6739e5708ce1 (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: Paul Gortmaker <paul.gortmaker@windriver.com>
Diffstat (limited to 'block')
| -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 4fab7c9df71d..510552a4bde2 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2559,8 +2559,11 @@ 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]); |