2.6.33-longterm review patch. If anyone has any objections, please let us 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> --- block/cfq-iosched.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -2537,8 +2537,11 @@ static void __cfq_exit_single_io_context 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]); _______________________________________________ stable mailing list stable@linux.kernel.org http://linux.kernel.org/mailman/listinfo/stable
