block: prevent division by zero in blk_rq_stat_sum()

The expression dst->nr_samples + src->nr_samples may
have zero value on overflow. It is necessary to add
a check to avoid division by zero.

Found by Linux Verification Center (linuxtesting.org) with Svace.

Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Link: https://lore.kernel.org/r/20240305134509.23108-1-r.smirnov@omp.ru
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-stat.c b/block/blk-stat.c
index 7ff76ae6c76a9531050af5e7a70c14af755eb403..e42c263e53fb995cd7c0b0d6d3de021cae05aae1 100644 (file)
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -27,7 +27,7 @@ void blk_rq_stat_init(struct blk_rq_stat *stat)
 /* src is a per-cpu stat, mean isn't initialized */
 void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
 {
-       if (!src->nr_samples)
+       if (dst->nr_samples + src->nr_samples <= dst->nr_samples)
                return;
 
        dst->min = min(dst->min, src->min);