From mboxrd@z Thu Jan 1 00:00:00 1970 From: ben.hutchings@codethink.co.uk (Ben Hutchings) Date: Fri, 09 Dec 2016 00:36:08 +0000 Subject: [cip-dev] [PATCH 4.4-cip 12/23] blk-mq: fix undefined behaviour in order_to_size() In-Reply-To: <1481243545.1860.156.camel@codethink.co.uk> References: <1481243545.1860.156.camel@codethink.co.uk> Message-ID: <1481243768.1860.168.camel@codethink.co.uk> To: cip-dev@lists.cip-project.org List-Id: cip-dev.lists.cip-project.org From: Bartlomiej Zolnierkiewicz commit b3a834b1596ac668df206aa2bb1f191c31f5f5e4 upstream. When this_order variable in blk_mq_init_rq_map() becomes zero the code incorrectly decrements the variable and passes the result to order_to_size() helper causing undefined behaviour: UBSAN: Undefined behaviour in block/blk-mq.c:1459:27 shift exponent 4294967295 is too large for 32-bit type 'unsigned int' CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc6-00072-g33656a1 #22 Fix the code by checking this_order variable for not having the zero value first. Reported-by: Meelis Roos Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism") Signed-off-by: Bartlomiej Zolnierkiewicz Signed-off-by: Jens Axboe Signed-off-by: Ben Hutchings --- block/blk-mq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index c3e461ec40e4..c58fdfdd9ea6 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1494,7 +1494,7 @@ static struct blk_mq_tags *blk_mq_init_rq_map(struct blk_mq_tag_set *set, int to_do; void *p; - while (left < order_to_size(this_order - 1) && this_order) + while (this_order && left < order_to_size(this_order - 1)) this_order--; do { -- 2.10.2 -- Ben Hutchings Software Developer, Codethink Ltd.