linux-kernel - Re: [PATCH] OOB read and write in mdp_prepare

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Date:   Thu, 29 Jun 2023 09:18:58 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     yqsun1997@...il.com, mchehab@...nel.org
Cc:     matthias.bgg@...il.com, angelogioacchino.delregno@...labora.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, 499671216@...com
Subject: Re: [PATCH] OOB read and write in mdp_prepare_buffer

Hi!

On 6/27/23 10:27, yqsun1997@...il.com wrote:
> From: yqsun1997 <yqsun1997@...il.com>
> 
> Because format in struct img_image_buffer max index is IMG_MAX_PLANES ==3,
> The num_planes max index is 8.so will be OOB like in mdp_prepare_buffer.
> 
> static void mdp_prepare_buffer(struct img_image_buffer *b,
>                                 struct mdp_frame *frame, struct vb2_buffer *vb)
> {
>          struct v4l2_pix_format_mplane *pix_mp = &frame->format.fmt.pix_mp;
>          unsigned int i;
> 
>          b->format.colorformat = frame->mdp_fmt->mdp_color;
>          b->format.ycbcr_prof = frame->ycbcr_prof;
>          for (i = 0; i < pix_mp->num_planes; ++i) {

Unless there is a bug in the driver, pix_mp->num_planes will never 
exceed 3. Userspace might certainly pass more than 3 planes, but only 
the first pix_mp->num_planes should ever be used.

If pix_mp->num_planes can ever be more than 3, then that would be the 
real bug.

Regards,

	Hans

>                  u32 stride = mdp_fmt_get_stride(frame->mdp_fmt,
>                          pix_mp->plane_fmt[i].bytesperline, i);
> 
>                  b->format.plane_fmt[i].stride = stride;  //oob
>                  ......
> 
> Signed-off-by: yqsun1997 <yqsun1997@...il.com>
> ---
>   drivers/media/platform/mediatek/mdp3/mtk-mdp3-type.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-type.h b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-type.h
> index ae0396806..e2e991a34 100644
> --- a/drivers/media/platform/mediatek/mdp3/mtk-mdp3-type.h
> +++ b/drivers/media/platform/mediatek/mdp3/mtk-mdp3-type.h
> @@ -11,7 +11,7 @@
>   
>   #define IMG_MAX_HW_INPUTS	3
>   #define IMG_MAX_HW_OUTPUTS	4
> -#define IMG_MAX_PLANES		3
> +#define IMG_MAX_PLANES		8
>   #define IMG_MAX_COMPONENTS	20
>   
>   struct img_crop {