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

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Date:   Fri, 10 Nov 2017 17:35:13 +0100
From:   Andrea Adami <andrea.adami@...il.com>
To:     Colin King <colin.king@...onical.com>
Cc:     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>,
        linux-mtd@...ts.infradead.org, kernel-janitors@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][V2] mtd: sharpslpart: fix overflow on block_adr calculation

On Wed, Nov 8, 2017 at 5:13 PM, Colin King <colin.king@...onical.com> wrote:
> 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
>

Thanks for spotting this,

Acked-by: Andrea Adami <andrea.adami@...il.com>