[FFmpeg-devel] [PATCH 1/6] avcodec/utils: allocate a line more for VC1 and WMV3

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: out of array read on 32bit
> Fixes: 54857/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VC1_fuzzer-5840588224462848
> 
> The chroma MC code reads over the currently allocated frame.
> Alternative fixes would be allocating a few bytes more at the end instead of a whole
> line extra or to adjust the threshold where the edge emu code is activated
> 
> 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/utils.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> index 2b63a498b9..1aa0a05a31 100644
> --- a/libavcodec/utils.c
> +++ b/libavcodec/utils.c
> @@ -321,6 +321,7 @@ void avcodec_align_dimensions2(AVCodecContext *s, int *width, int *height,
>      *width  = FFALIGN(*width, w_align);
>      *height = FFALIGN(*height, h_align);
>      if (s->codec_id == AV_CODEC_ID_H264 || s->lowres ||
> +        s->codec_id == AV_CODEC_ID_VC1  || s->codec_id == AV_CODEC_ID_WMV3 ||
>          s->codec_id == AV_CODEC_ID_VP5  || s->codec_id == AV_CODEC_ID_VP6 ||
>          s->codec_id == AV_CODEC_ID_VP6F || s->codec_id == AV_CODEC_ID_VP6A
>      ) {

Does this only happen on 32bit systems? If so, why?

- Andreas