The value of an arithmetic expression directory * master->erasesize is
subject to overflow due to a failure to cast operands to a larger data
type before perfroming arithmetic

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

Signed-off-by: Denis Arefev <arefev@swemel.ru>
---
 drivers/mtd/parsers/redboot.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/parsers/redboot.c b/drivers/mtd/parsers/redboot.c
index a16b42a88581..3b55b676ca6b 100644
--- a/drivers/mtd/parsers/redboot.c
+++ b/drivers/mtd/parsers/redboot.c
@@ -102,7 +102,7 @@ static int parse_redboot_partitions(struct mtd_info *master,
 			offset -= master->erasesize;
 		}
 	} else {
-		offset = directory * master->erasesize;
+		offset = (unsigned long) directory * master->erasesize;
 		while (mtd_block_isbad(master, offset)) {
 			offset += master->erasesize;
 			if (offset == master->size)
-- 
2.25.1

On Fri, 2024-03-15 at 09:37:58 UTC, Denis Arefev wrote:
> The value of an arithmetic expression directory * master->erasesize is
> subject to overflow due to a failure to cast operands to a larger data
> type before perfroming arithmetic
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Denis Arefev <arefev@swemel.ru>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel

On Fri, Mar 15, 2024 at 12:37:58PM +0300, Denis Arefev wrote:
> The value of an arithmetic expression directory * master->erasesize is
> subject to overflow due to a failure to cast operands to a larger data
> type before perfroming arithmetic

...

> -		offset = directory * master->erasesize;
> +		offset = (unsigned long) directory * master->erasesize;

Usage of explicit casting can be avoided by using size_mul() from overflow.h.
Usually explicit castings are prone to subtle errors.

-- 
With Best Regards,
Andy Shevchenko