The patch below does not apply to the 3.0-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.
thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9b50902db5eb8a220160fb89e95aa11967998d12 Mon Sep 17 00:00:00 2001 From: Jens Axboe <[email protected]> Date: Sun, 5 Jun 2011 06:01:13 +0200 Subject: [PATCH] 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: [email protected] Signed-off-by: Jens Axboe <[email protected]> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index a2fb14b..000719c 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]); _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
