linux-kernel - [PATCH][V2] mtd: sharpslpart: fix overflow on block

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Date:   Wed,  8 Nov 2017 16:13:23 +0000
From:   Colin King <colin.king@...onical.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Andrea Adami <andrea.adami@...il.com>,
        linux-mtd@...ts.infradead.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][V2] mtd: sharpslpart: fix overflow on block_adr calculation

From: Colin Ian King <colin.king@...onical.com>

Multiplying block_num and mtd->erasesize may potentially overflow
as they are both unsigned ints and so the multiplication is evaluated
in unsigned int arithmetic.  Cast block_adr to off_t to ensure
multiplication is off_t sized to avoid any potential overflow.

Detected by CoverityScan, CID#1461264 ("Unintentional integer overflow")

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/mtd/parsers/sharpslpart.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/parsers/sharpslpart.c b/drivers/mtd/parsers/sharpslpart.c
index 5fe0079ea5ed..0ddb79ac390d 100644
--- a/drivers/mtd/parsers/sharpslpart.c
+++ b/drivers/mtd/parsers/sharpslpart.c
@@ -192,7 +192,7 @@ static int sharpsl_nand_init_ftl(struct mtd_info *mtd, struct sharpsl_ftl *ftl)
 
 	/* create physical-logical table */
 	for (block_num = 0; block_num < phymax; block_num++) {
-		block_adr = block_num * mtd->erasesize;
+		block_adr = (loff_t)block_num * mtd->erasesize;
 
 		if (mtd_block_isbad(mtd, block_adr))
 			continue;
@@ -244,7 +244,7 @@ static int sharpsl_nand_read_laddr(struct mtd_info *mtd,
 		return -EINVAL;
 
 	block_num = ftl->log2phy[log_num];
-	block_adr = block_num * mtd->erasesize;
+	block_adr = (loff_t)block_num * mtd->erasesize;
 	block_ofs = mtd_mod_by_eb((u32)from, mtd);
 
 	err = mtd_read(mtd, block_adr + block_ofs, len, &retlen, buf);
-- 
2.14.1