From 571190739a49ae31fc955139f0c5576215229e1d Mon Sep 17 00:00:00 2001 From: Bartlomiej Zolnierkiewicz Date: Mon, 16 May 2016 09:54:47 -0600 Subject: [PATCH] blk-mq: fix undefined behaviour in order_to_size() 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: Greg Kroah-Hartman Signed-off-by: Lee Jones Change-Id: Ibf5ca9d79fe3580fe057d27da05cb29348b53781 --- 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 4b839c117c566..c5eeb21c9c906 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1339,7 +1339,7 @@ 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 {