dm stats: fix divide by zero if 'number_of_areas' arg is zero

If the number_of_areas argument was zero the kernel would crash on
div-by-zero.  Add better input validation.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v3.12+

diff --git a/drivers/md/dm-stats.c b/drivers/md/dm-stats.c
index 492fe6a..d1fd31a 100644 (file)
--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -792,6 +792,8 @@ static int message_stats_create(struct mapped_device *md,
                return -EINVAL;
 
        if (sscanf(argv[2], "/%u%c", &divisor, &dummy) == 1) {
+               if (!divisor)
+                       return -EINVAL;
                step = end - start;
                if (do_div(step, divisor))
                        step++;