linux-kernel - Re: [PATCH v3] media: platform: mtk-mdp3: Add missing check and free for ida

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Date:   Thu, 9 Feb 2023 14:21:13 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>, mchehab@...nel.org,
        matthias.bgg@...il.com, moudy.ho@...iatek.com,
        daoyuan.huang@...iatek.com, hverkuil-cisco@...all.nl
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3] media: platform: mtk-mdp3: Add missing check and free
 for ida_alloc

Il 09/02/23 10:25, Jiasheng Jiang ha scritto:
> Add the check for the return value of the ida_alloc in order to avoid
> NULL pointer dereference.
> Moreover, free allocated "ctx->id" if mdp_m2m_open fails later in order
> to avoid memory leak.
> 
> Fixes: 61890ccaefaf ("media: platform: mtk-mdp3: add MediaTek MDP3 driver")
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog:
> 
> v2 -> v3:
> 
> 1. Fix the goto label.
> 
> v1 -> v2:
> 
> 1. Fix the check for the ida_alloc.
> ---
>   drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
> index 5f74ea3b7a52..a2d204e90aa4 100644
> --- a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
> +++ b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-m2m.c
> @@ -567,6 +567,11 @@ static int mdp_m2m_open(struct file *file)
>   	}
>   
>   	ctx->id = ida_alloc(&mdp->mdp_ida, GFP_KERNEL);
> +	if (ctx->id < 0) {

There's one main not-so-minor issue here: ctx->id is u32.
Unsigned types cannot evaluate less than zero: they're .. unsigned!

There's your fix:
	ret = ida_alloc ...
	if (ret)
		....
	ctx->id = ret;


Enjoy.

Regards,
Angelo