[PATCH][mtd-next] mtd: sharpslpart: fix overflow on block_adr calculation

[Colin King]

From: Colin Ian King <colin.king at canonical.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")

Fixes: fff1e32a50c0 ("mtd: sharpslpart: Add sharpslpart partition parser")
Signed-off-by: Colin Ian King <colin.king at canonical.com>
---
 drivers/mtd/parsers/sharpslpart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/parsers/sharpslpart.c b/drivers/mtd/parsers/sharpslpart.c
index 5fe0079ea5ed..b1d97aa3bac4 100644
--- a/drivers/mtd/parsers/sharpslpart.c
+++ b/drivers/mtd/parsers/sharpslpart.c
@@ -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