Re: [PATCH] drm/mediatek/dp: fix spurious kfree()

From: Jani Nikula <jani.nikula@intel.com>
To: Michael Walle <mwalle@kernel.org>,
	Chun-Kuang Hu <chunkuang.hu@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>
Cc: Chen-Yu Tsai <wenst@chromium.org>,
	linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Michael Walle <mwalle@kernel.org>
Subject: Re: [PATCH] drm/mediatek/dp: fix spurious kfree()
Date: Fri, 17 May 2024 16:12:25 +0300	[thread overview]
Message-ID: <87v83ca8g6.fsf@intel.com> (raw)
In-Reply-To: <20240517093024.1702750-1-mwalle@kernel.org>

On Fri, 17 May 2024, Michael Walle <mwalle@kernel.org> wrote:
> drm_edid_to_sad() might return an error or just zero. If that is the
> case, we must not free the SADs because there was no allocation in
> the first place.
>
> Fixes: dab12fa8d2bd ("drm/mediatek/dp: fix memory leak on ->get_edid callback audio detection")
> Signed-off-by: Michael Walle <mwalle@kernel.org>
> ---
>  drivers/gpu/drm/mediatek/mtk_dp.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> index 536366956447..ada12927bbac 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> @@ -2073,9 +2073,15 @@ static const struct drm_edid *mtk_dp_edid_read(struct drm_bridge *bridge,
>  		 */
>  		const struct edid *edid = drm_edid_raw(drm_edid);
>  		struct cea_sad *sads;

I suppose I would've just initialized sads = NULL; and be done with it.

But *shrug*.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

> +		int ret;
>  
> -		audio_caps->sad_count = drm_edid_to_sad(edid, &sads);
> -		kfree(sads);
> +		ret = drm_edid_to_sad(edid, &sads);
> +		/* Ignore any errors */
> +		if (ret < 0)
> +			ret = 0;
> +		if (ret)
> +			kfree(sads);
> +		audio_caps->sad_count = ret;
>  
>  		/*
>  		 * FIXME: This should use connector->display_info.has_audio from

-- 
Jani Nikula, Intel