linux-kernel - Re: [PATCH] drm/meson: Cast mode->clock to unsigned long long

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Message-ID: <d5a8e781-6936-4c83-83d1-92daa2da8ca2@wanadoo.fr>
Date: Tue, 29 Apr 2025 23:00:01 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: I Hsin Cheng <richard120310@...il.com>, neil.armstrong@...aro.org
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, dri-devel@...ts.freedesktop.org,
 linux-amlogic@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, skhan@...uxfoundation.org
Subject: Re: [PATCH] drm/meson: Cast mode->clock to unsigned long long

Le 29/04/2025 à 21:07, I Hsin Cheng a écrit :
> Coverity scan reported the usage of "mode->clock * 1000" may lead to
> integer overflow. Cast the type of "mode->clock" to "unsigned long long"
> 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>
> ---
>   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..fe3d3ff7c432 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 = (unsigned long long) mode->clock * 1000;

Hi,

maybe, using 1000ULL instead would do the same, but would be less verbose?

CJ

>   
>   	/* 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 = (unsigned long long) mode->clock * 1000;
>   	unsigned long long phy_freq;
>   	unsigned long long vclk_freq;
>   	unsigned long long venc_freq;