[FFmpeg-devel] [PATCH 2/3] avcodec/exr: Fix overflow with many blocks

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: signed integer overflow: 1073741827 * 8 cannot be represented in type 'int'
> Fixes: 25621/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EXR_fuzzer-6304841641754624
> 
> 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/exr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/exr.c b/libavcodec/exr.c
> index c80e8eb5e0..8621a8cfe4 100644
> --- a/libavcodec/exr.c
> +++ b/libavcodec/exr.c
> @@ -1783,7 +1783,7 @@ static int decode_frame(AVCodecContext *avctx, void *data,
>      if ((ret = ff_thread_get_buffer(avctx, &frame, 0)) < 0)
>          return ret;
>  
> -    if (bytestream2_get_bytes_left(&s->gb) < nb_blocks * 8)
> +    if (bytestream2_get_bytes_left(&s->gb) < nb_blocks * 8L)

Does this have an advantage over dividing by 8?

>          return AVERROR_INVALIDDATA;
>  
>      // check offset table and recreate it if need
>