From: Bartlomiej Zolnierkiewicz b.zolnierkie@samsung.com
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 mroos@linux.ee Fixes: 320ae51feed5 ("blk-mq: new multi-queue block IO queueing mechanism") Signed-off-by: Bartlomiej Zolnierkiewicz b.zolnierkie@samsung.com Signed-off-by: Jens Axboe axboe@fb.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- block/blk-mq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1491,7 +1491,7 @@ 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 {