Re: [FFmpeg-devel] [PATCH] avformat/rawvideodec: check packet size

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Michael Niedermayer:
> Fixes: division by zero
> Fixes: 43347/clusterfuzz-testcase-minimized-ffmpeg_dem_V210X_fuzzer-5846911637127168
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavformat/rawvideodec.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/libavformat/rawvideodec.c b/libavformat/rawvideodec.c
> index 68547fc50ff..7581ba2c7d2 100644
> --- a/libavformat/rawvideodec.c
> +++ b/libavformat/rawvideodec.c
> @@ -100,6 +100,8 @@ static int rawvideo_read_header(AVFormatContext *ctx)
>          if (packet_size < 0)
>              return packet_size;
>      }
> +    if (packet_size == 0)
> +        return AVERROR_INVALIDDATA;
>  
>      st->codecpar->format = pix_fmt;
>      ctx->packet_size = packet_size;
> 

1. I agree with Lance that AVERROR(EINVAL) is the proper error code;
after all, the dimensions are based upon options and not read from the
input.
2. The dimensions were checked by av_image_check_size() before
41f213c3bf629d549400e935e7f123e6cfa959ab.
3. The same can happen with bitpacked. Your check should also catch this.
4. But I don't see anything that actually ensures that the
multiplications do not overflow.

- Andreas
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