[FFmpeg-devel] [PATCH V3] lavfi/nlmeans: Checking number precision when computing integral images

[Michael Niedermayer]

On Thu, Mar 07, 2019 at 09:45:12AM +0800, Jun Zhao wrote:
> From: Jun Zhao <barryjzhao at tencent.com>
> 
> accumulation of 8-bits uint_8 (uint8_t *src) into 32-bits (uint32_t *ii)
> data type, it will have a risk of an integral value becoming larger than
> the 32-bits integer capacity and resulting in an integer overflow. For
> this risk, add a checking with warning message.
> 
> Signed-off-by: Jun Zhao <barryjzhao at tencent.com>
> ---
>  libavfilter/vf_nlmeans.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)
> 
> diff --git a/libavfilter/vf_nlmeans.c b/libavfilter/vf_nlmeans.c
> index dcb5a03..9876aae 100644
> --- a/libavfilter/vf_nlmeans.c
> +++ b/libavfilter/vf_nlmeans.c
> @@ -236,6 +236,13 @@ static void compute_ssd_integral_image(const NLMeansDSPContext *dsp,
>      // adjusted end x position of the safe area after width of the safe area gets aligned
>      const int endx_safe = startx_safe + safe_pw;
>  
> +    // accumulation of 8-bits uint_8 (uint8_t *src) into 32-bits (uint32_t *ii)
> +    // data type, it will have a risk of an integral value becoming larger than
> +    // the 32-bits integer capacity and resulting in an integer overflow.
> +    if ((UINT32_MAX / (uint64_t)w) < (255 * (uint64_t)h))
> +        av_log(NULL, AV_LOG_WARNING,
> +               "image (%d x %d) integral value may overflow.\n", w ,h);

Printing a warning is not an adequate response for a integer overflow.
Such thing is undefined behavior (in case signed of signed int) and must
not occur.

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20190307/a7e4bb3b/attachment.sig>