From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932557AbcHNSOL (ORCPT ); Sun, 14 Aug 2016 14:14:11 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:54909 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932297AbcHNR6e (ORCPT ); Sun, 14 Aug 2016 13:58:34 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Meelis Roos" , "Jens Axboe" , "Bartlomiej Zolnierkiewicz" Date: Sat, 13 Aug 2016 18:42:51 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 084/305] blk-mq: fix undefined behaviour in order_to_size() In-Reply-To: X-SA-Exim-Connect-IP: 92.40.249.202 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.37-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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(-) --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1385,7 +1385,7 @@ static struct blk_mq_tags *blk_mq_init_r 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 {