linux-kernel - Re: [PATCH -next] media: rkvdec: Fix memset size error

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Message-ID: <107f5083-3545-770d-4d63-57c6829ef95a@arm.com>
Date:   Fri, 17 Jun 2022 09:10:57 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Zhang Zekun <zhangzekun11@...wei.com>,
        ezequiel@...guardiasur.com.ar, mchehab@...nel.org,
        gregkh@...uxfoundation.org, andrzej.p@...labora.com,
        hverkuil-cisco@...all.nl
Cc:     linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] media: rkvdec: Fix memset size error

On 2022-06-17 08:31, Zhang Zekun wrote:
> 'dma_alloc_coherent()' alloc a 'RKVDEC_VP9_COUNT_SIZE' size area to
> 'unsigned char *count_tbl', however, the memset() bellow only set
> 'sizeof(*count_tbl)', which equals to 1, bytes to zero. This can
>   cause unexpected error.

Have you observed an error in practice? Given that it's been part of the 
dma_alloc_coherent() API to return a zeroed buffer for several years now 
- see 750afb08ca71 ("cross-tree: phase out dma_zalloc_coherent()") - 
this memset shouldn't be needed either way.

Robin.

> Fixes: f25709c4ff15 ("media: rkvdec: Add the VP9 backend")
> Signed-off-by: Zhang Zekun <zhangzekun11@...wei.com>
> ---
>   drivers/staging/media/rkvdec/rkvdec-vp9.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/media/rkvdec/rkvdec-vp9.c b/drivers/staging/media/rkvdec/rkvdec-vp9.c
> index 311a12656072..3ad303a3de48 100644
> --- a/drivers/staging/media/rkvdec/rkvdec-vp9.c
> +++ b/drivers/staging/media/rkvdec/rkvdec-vp9.c
> @@ -1026,7 +1026,7 @@ static int rkvdec_vp9_start(struct rkvdec_ctx *ctx)
>   
>   	vp9_ctx->count_tbl.size = RKVDEC_VP9_COUNT_SIZE;
>   	vp9_ctx->count_tbl.cpu = count_tbl;
> -	memset(count_tbl, 0, sizeof(*count_tbl));
> +	memset(count_tbl, 0, RKVDEC_VP9_COUNT_SIZE);
>   	rkvdec_init_v4l2_vp9_count_tbl(ctx);
>   
>   	return 0;