From:   Zhong Jinghua <zhongjinghua@huawei.com>
To:     <axboe@kernel.dk>
CC:     <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <zhongjinghua@huawei.com>, <yi.zhang@huawei.com>,
        <yukuai3@huawei.com>, <houtao1@huawei.com>, <yangerkun@huawei.com>
Subject: [PATCH-next] loop: loop_set_status_from_info() check before assignment
Date:   Mon, 6 Feb 2023 09:57:39 +0800
Message-ID: <20230206015739.4171377-1-zhongjinghua@huawei.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7BIT
Content-Type:   text/plain; charset=US-ASCII
Precedence: bulk

In loop_set_status_from_info(), lo->lo_offset and lo->lo_sizelimit should
be checked before reassignment, because if an overflow error occurs, the
original correct value will be changed to the wrong value, and it will not
be changed back.

Modifying to the wrong value logic is always not quiet right, we hope to
optimize this.

Signed-off-by: Zhong Jinghua <zhongjinghua@huawei.com>
---
 drivers/block/loop.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 1518a6423279..5eb5915d1a97 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -977,13 +977,13 @@ loop_set_status_from_info(struct loop_device *lo,
 		return -EINVAL;
 	}
 
+	/* Avoid assigning overflowing values */
+	if (info->lo_offset > LLONG_MAX || info->lo_sizelimit > LLONG_MAX)
+		return -EOVERFLOW;
+
 	lo->lo_offset = info->lo_offset;
 	lo->lo_sizelimit = info->lo_sizelimit;
 
-	/* loff_t vars have been assigned __u64 */
-	if (lo->lo_offset < 0 || lo->lo_sizelimit < 0)
-		return -EOVERFLOW;
-
 	memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
 	lo->lo_file_name[LO_NAME_SIZE-1] = 0;
 	lo->lo_flags = info->lo_flags;
-- 
2.31.1