linux-kernel - Re: [PATCH] drm: zynqmp_dp: Fix integer overflow in zynqmp_dp_rate

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Message-ID: <20241211125936.GA23711@pendragon.ideasonboard.com>
Date: Wed, 11 Dec 2024 14:59:36 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Karol Przybylski <karprzy7@...il.com>
Cc: tomi.valkeinen@...asonboard.com, maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
	simona@...ll.ch, michal.simek@....com,
	dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: zynqmp_dp: Fix integer overflow in
 zynqmp_dp_rate_get()

Hi Karol,

Thank you for the patch.

On Wed, Dec 11, 2024 at 01:20:26PM +0100, Karol Przybylski wrote:
> This patch fixes a potential integer overflow in the zynqmp_dp_rate_get() function.
> 
> The issue comes up when the expression drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000 is evaluated using 32-bit arithmetic.

Please wrap your commit message text to 82 columns.

> 
> Now the constant is casted to compatible u64 type.
> 
> Resolves CID 1636340 and CID 1635811
> 

Does this need a Fixes: tag ? How about 'Cc: stable@...r.kernel.org' to
get it backported to stable kernels ?

> Signed-off-by: Karol Przybylski <karprzy7@...il.com>
> ---
>  drivers/gpu/drm/xlnx/zynqmp_dp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index 25c5dc61e..55e92344b 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -2190,7 +2190,7 @@ static int zynqmp_dp_rate_get(void *data, u64 *val)
>  	struct zynqmp_dp *dp = data;
>  
>  	mutex_lock(&dp->lock);
> -	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000;
> +	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * (u64)10000;

You can also make the integer a 64-bit constant with

	*val = drm_dp_bw_code_to_link_rate(dp->test.bw_code) * 10000ULL;

>  	mutex_unlock(&dp->lock);
>  	return 0;
>  }

-- 
Regards,

Laurent Pinchart