linux-kernel - Re: [PATCH 4/5] drm/mediatek: Add casting before assign

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Date:   Mon, 12 Jun 2023 09:05:15 +0000
From:   CK Hu (胡俊光) <ck.hu@...iatek.com>
To:     Jason-JH Lin (林睿祥) 
        <Jason-JH.Lin@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        Jason-ch Chen (陳建豪) 
        <Jason-ch.Chen@...iatek.com>,
        Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        Rex-BC Chen (陳柏辰) 
        <Rex-BC.Chen@...iatek.com>
Subject: Re: [PATCH 4/5] drm/mediatek: Add casting before assign

Hi, Jason:

On Fri, 2023-04-07 at 14:46 +0800, Jason-JH.Lin wrote:
> Add casting before assign to avoid the unintentional integer overflow
> or unintended sign extension.
> 
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> Fixes: 1a64a7aff8da ("drm/mediatek: Fix cursor plane no update")
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_gem.c   |  2 +-
>  drivers/gpu/drm/mediatek/mtk_drm_plane.c | 20 +++++++++++---------
>  2 files changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> index 9b8f72ed12e4..537e83b95001 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_gem.c
> @@ -121,7 +121,7 @@ int mtk_drm_gem_dumb_create(struct drm_file
> *file_priv, struct drm_device *dev,
>  	int ret;
>  
>  	args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
> -	args->size = args->pitch * args->height;
> +	args->size = (unsigned long)args->pitch * args->height;

The prototype is

struct drm_mode_create_dump {
	__u32 height;
	__u32 pitch;
	__u64 size;
};

Do you want to case to "__u64"?

>  
>  	mtk_gem = mtk_drm_gem_create(dev, args->size, false);
>  	if (IS_ERR(mtk_gem))
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> index 31f9420aff6f..a1337f386bbf 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> @@ -140,7 +140,7 @@ static void mtk_plane_update_new_state(struct
> drm_plane_state *new_state,
>  	struct drm_framebuffer *fb = new_state->fb;
>  	struct drm_gem_object *gem;
>  	struct mtk_drm_gem_obj *mtk_gem;
> -	unsigned int pitch, format;
> +	unsigned int pitch, format, cpp;
>  	u64 modifier;
>  	dma_addr_t addr;
>  	dma_addr_t hdr_addr = 0;
> @@ -151,11 +151,12 @@ static void mtk_plane_update_new_state(struct
> drm_plane_state *new_state,
>  	addr = mtk_gem->dma_addr;
>  	pitch = fb->pitches[0];
>  	format = fb->format->format;
> +	cpp = (unsigned int)fb->format->cpp[0];
>  	modifier = fb->modifier;
>  
>  	if (modifier == DRM_FORMAT_MOD_LINEAR) {
> -		addr += (new_state->src.x1 >> 16) * fb->format->cpp[0];
> -		addr += (new_state->src.y1 >> 16) * pitch;
> +		addr += (dma_addr_t)(new_state->src.x1 >> 16) * cpp;
> +		addr += (dma_addr_t)(new_state->src.y1 >> 16) * pitch;
>  	} else {
>  		int width_in_blocks = ALIGN(fb->width,
> AFBC_DATA_BLOCK_WIDTH)
>  				      / AFBC_DATA_BLOCK_WIDTH;
> @@ -167,17 +168,18 @@ static void mtk_plane_update_new_state(struct
> drm_plane_state *new_state,
>  
>  		hdr_pitch = width_in_blocks * AFBC_HEADER_BLOCK_SIZE;
>  		pitch = width_in_blocks * AFBC_DATA_BLOCK_WIDTH *
> -			AFBC_DATA_BLOCK_HEIGHT * fb->format->cpp[0];
> +			AFBC_DATA_BLOCK_HEIGHT * cpp;
>  
>  		hdr_size = ALIGN(hdr_pitch * height_in_blocks,
> AFBC_HEADER_ALIGNMENT);
>  
> -		hdr_addr = addr + hdr_pitch * y_offset_in_blocks +
> -			   AFBC_HEADER_BLOCK_SIZE * x_offset_in_blocks;
> +		hdr_addr = addr +
> +			   (dma_addr_t)hdr_pitch * y_offset_in_blocks +
> +			   (dma_addr_t)AFBC_HEADER_BLOCK_SIZE *
> x_offset_in_blocks;
>  		/* The data plane is offset by 1 additional block. */
>  		addr = addr + hdr_size +
> -		       pitch * y_offset_in_blocks +
> -		       AFBC_DATA_BLOCK_WIDTH * AFBC_DATA_BLOCK_HEIGHT *
> -		       fb->format->cpp[0] * (x_offset_in_blocks + 1);
> +		       (dma_addr_t)pitch * y_offset_in_blocks +
> +		       (dma_addr_t)AFBC_DATA_BLOCK_WIDTH *
> AFBC_DATA_BLOCK_HEIGHT *
> +		       (dma_addr_t)cpp * (x_offset_in_blocks + 1);
>  	}

I would like you to add a variable 'u32 offset' for this calculating,
and I think u32 is enough for this calculating and it's not necessary
to do any casting.

Regards,
CK

>  
>  	mtk_plane_state->pending.enable = true;