[FFmpeg-devel] [PATCH] avcodec/zmbv: Check decomp_size

[Tomas Härdin]

On 2017-08-16 05:04, Michael Niedermayer wrote:
> Fixes: OOM
> Fixes: 2710/clusterfuzz-testcase-minimized-4750001420894208
>
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>   libavcodec/zmbv.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/zmbv.c b/libavcodec/zmbv.c
> index f126515bd1..861098a0f2 100644
> --- a/libavcodec/zmbv.c
> +++ b/libavcodec/zmbv.c
> @@ -589,8 +589,12 @@ static av_cold int decode_init(AVCodecContext *avctx)
>       // Needed if zlib unused or init aborted before inflateInit
>       memset(&c->zstream, 0, sizeof(z_stream));
>   
> -    c->decomp_size = (avctx->width + 255) * 4 * (avctx->height + 64);
> +    if ((avctx->width + 255ULL) * (avctx->height + 64ULL) > avctx->max_pixels) {

Are width and height constrained somewhere? If both end up around 1<<32 
then the multiplication can overflow.

> +        av_log(avctx, AV_LOG_ERROR, "Internal buffer larger than max_pixels\n");
> +        return AVERROR_INVALIDDATA;
> +    }
>   
> +    c->decomp_size = (avctx->width + 255) * 4 * (avctx->height + 64);

Use 255ULL and 64ULL maybe? It's almost conceivable that you could have 
a file constructed to be (1<<31 - 255)x1 that passes the max_pixels check

/Tomas