2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: Jens Axboe <jax...@fusionio.com> 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 <jax...@fusionio.com> Signed-off-by: Greg Kroah-Hartman <gre...@suse.de> Signed-off-by: Andi Kleen <a...@linux.intel.com> --- block/cfq-iosched.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) Index: linux-2.6.35.y/block/cfq-iosched.c =================================================================== --- linux-2.6.35.y.orig/block/cfq-iosched.c +++ linux-2.6.35.y/block/cfq-iosched.c @@ -2615,8 +2615,11 @@ static void __cfq_exit_single_io_context 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 stable@linux.kernel.org http://linux.kernel.org/mailman/listinfo/stable
