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From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Cc: Roman Smirnov <r.smirnov@omp.ru>,
	Sergey Shtylyov <s.shtylyov@omp.ru>,
	Jens Axboe <axboe@kernel.dk>,
	Sasha Levin <sashal@kernel.org>,
	linux-block@vger.kernel.org
Subject: [PATCH AUTOSEL 6.8 84/98] block: prevent division by zero in blk_rq_stat_sum()
Date: Fri, 29 Mar 2024 08:37:55 -0400
Message-ID: <20240329123919.3087149-84-sashal@kernel.org>
In-Reply-To: <20240329123919.3087149-1-sashal@kernel.org>
References: <20240329123919.3087149-1-sashal@kernel.org>
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From: Roman Smirnov <r.smirnov@omp.ru>

[ Upstream commit 93f52fbeaf4b676b21acfe42a5152620e6770d02 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 block/blk-stat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-stat.c b/block/blk-stat.c
index 7ff76ae6c76a9..e42c263e53fb9 100644
--- 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);
-- 
2.43.0