linux-kernel - Re: [PATCH 4/8] i2c: ov9650: fix potential integer overflow in __ov965x_set_frame

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Date:   Fri, 2 Feb 2018 11:22:57 +0200
From:   Sakari Ailus <sakari.ailus@....fi>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: Re: [PATCH 4/8] i2c: ov9650: fix potential integer overflow in
 __ov965x_set_frame_interval

On Mon, Jan 29, 2018 at 06:32:01PM -0600, Gustavo A. R. Silva wrote:
> Cast fi->interval.numerator to u64 in order to avoid a potential integer
> overflow. This variable is being used in a context that expects an
> expression of type u64.
> 
> Addresses-Coverity-ID: 1324146 ("Unintentional integer overflow")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/media/i2c/ov9650.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
> index e519f27..c674a49 100644
> --- a/drivers/media/i2c/ov9650.c
> +++ b/drivers/media/i2c/ov9650.c
> @@ -1130,7 +1130,7 @@ static int __ov965x_set_frame_interval(struct ov965x *ov965x,
>  	if (fi->interval.denominator == 0)
>  		return -EINVAL;
>  
> -	req_int = (u64)(fi->interval.numerator * 10000) /
> +	req_int = (u64)fi->interval.numerator * 10000 /
>  		fi->interval.denominator;

This requires do_div(). I've applied the patch with this change:

diff --git a/drivers/media/i2c/ov9650.c b/drivers/media/i2c/ov9650.c
index 88276dba828d..5bea31cd41aa 100644
--- a/drivers/media/i2c/ov9650.c
+++ b/drivers/media/i2c/ov9650.c
@@ -1136,8 +1136,8 @@ static int __ov965x_set_frame_interval(struct ov965x *ov965x,
 	if (fi->interval.denominator == 0)
 		return -EINVAL;
 
-	req_int = (u64)fi->interval.numerator * 10000 /
-		fi->interval.denominator;
+	req_int = (u64)fi->interval.numerator * 10000;
+	do_div(req_int, fi->interval.denominator);
 
 	for (i = 0; i < ARRAY_SIZE(ov965x_intervals); i++) {
 		const struct ov965x_interval *iv = &ov965x_intervals[i];

>  
>  	for (i = 0; i < ARRAY_SIZE(ov965x_intervals); i++) {
> -- 
> 2.7.4
> 

-- 
Sakari Ailus
e-mail: sakari.ailus@....fi