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authorJens Axboe <jaxboe@fusionio.com>2011-06-05 06:01:13 +0200
committerJens Axboe <jaxboe@fusionio.com>2011-06-06 05:57:21 +0200
commit9b50902db5eb8a220160fb89e95aa11967998d12 (patch)
treead025360c616398f2b0aea1f0789a2f8174496b1 /block
parent796d5116c407690b14fd5bda136aa67a39e7061a (diff)
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cfq-iosched: fix locking around ioc->ioc_data assignment
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. Cc: stable@kernel.org Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
-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 a2fb14bb140..000719c484c 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2767,8 +2767,11 @@ 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]);