linux-kernel - Re: [PATCH v2] drm/meson: Use 1000ULL when operating with mode->clock

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Message-ID: <6d2f35ee-1b33-40b6-b164-ab4480110e49@linaro.org>
Date: Fri, 9 May 2025 17:35:35 +0200
From: neil.armstrong@...aro.org
To: I Hsin Cheng <richard120310@...il.com>
Cc: maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
 tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
 khilman@...libre.com, jbrunet@...libre.com,
 martin.blumenstingl@...glemail.com, christophe.jaillet@...adoo.fr,
 skhan@...uxfoundation.org, dri-devel@...ts.freedesktop.org,
 linux-amlogic@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/meson: Use 1000ULL when operating with mode->clock

On 05/05/2025 20:43, I Hsin Cheng wrote:
> Coverity scan reported the usage of "mode->clock * 1000" may lead to
> integer overflow. Use "1000ULL" instead of "1000"
> when utilizing it to avoid potential integer overflow issue.
> 
> Link: https://scan5.scan.coverity.com/#/project-view/10074/10063?selectedIssue=1646759
> Signed-off-by: I Hsin Cheng <richard120310@...il.com>

Could you add a Fixes tag ?

Thanks,
Neil

> ---
> Changelog:
> 
> v1 -> v2:
> 	- Use 1000ULL instead of casting the type of "mode->clock"
> 	- Refine commit title and message
> 	- Fix the issue for the evaluation inside drm_mode_status
> 	  meson_encoder_hdmi_mode_valid() as well
> 
> Christophe,
> Thanks for your review and your suggestion, I think I should add a tag
> for you,too, but I'm not sure what should I add, if you would be so kind
> please let me know how should I tag you in the patch.
> 
> Best regards,
> I Hsin Cheng
> ---
>   drivers/gpu/drm/meson/meson_encoder_hdmi.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_encoder_hdmi.c b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> index 7752d8ac85f0..c08fa93e50a3 100644
> --- a/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> +++ b/drivers/gpu/drm/meson/meson_encoder_hdmi.c
> @@ -75,7 +75,7 @@ static void meson_encoder_hdmi_set_vclk(struct meson_encoder_hdmi *encoder_hdmi,
>   	unsigned long long venc_freq;
>   	unsigned long long hdmi_freq;
>   
> -	vclk_freq = mode->clock * 1000;
> +	vclk_freq = mode->clock * 1000ULL;
>   
>   	/* For 420, pixel clock is half unlike venc clock */
>   	if (encoder_hdmi->output_bus_fmt == MEDIA_BUS_FMT_UYYVYY8_0_5X24)
> @@ -123,7 +123,7 @@ static enum drm_mode_status meson_encoder_hdmi_mode_valid(struct drm_bridge *bri
>   	struct meson_encoder_hdmi *encoder_hdmi = bridge_to_meson_encoder_hdmi(bridge);
>   	struct meson_drm *priv = encoder_hdmi->priv;
>   	bool is_hdmi2_sink = display_info->hdmi.scdc.supported;
> -	unsigned long long clock = mode->clock * 1000;
> +	unsigned long long clock = mode->clock * 1000ULL;
>   	unsigned long long phy_freq;
>   	unsigned long long vclk_freq;
>   	unsigned long long venc_freq;