[FFmpeg-devel] [PATCH 3/3] avformat/rmdec: Check codec_length without overflow

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: signed integer overflow: 2147483647 + 64 cannot be represented in type 'int'
> Fixes: 30333/clusterfuzz-testcase-minimized-ffmpeg_dem_RM_fuzzer-5175286983426048
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavformat/rmdec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavformat/rmdec.c b/libavformat/rmdec.c
> index 521b9d0e8c..613fb407df 100644
> --- a/libavformat/rmdec.c
> +++ b/libavformat/rmdec.c
> @@ -223,7 +223,7 @@ static int rm_read_audio_stream_info(AVFormatContext *s, AVIOContext *pb,
>                  if (version == 5)
>                      avio_r8(pb);
>                  codecdata_length = avio_rb32(pb);
> -                if(codecdata_length + AV_INPUT_BUFFER_PADDING_SIZE <= (unsigned)codecdata_length){
> +                if(codecdata_length < 0 || codecdata_length > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE){
>                      av_log(s, AV_LOG_ERROR, "codecdata_length too large\n");
>                      return -1;
>                  }
> 
The first of these checks can be avoided by making codecdata_length
unsigned.

- Andreas