[FFmpeg-devel] [PATCH] avcodec/vvc_mp4toannexb: check the return of bytestream2_get_buffer

[Andreas Rheinhardt]

Nuo Mi:
> Fixes: fuzzer timeout
> Fixes: 65253/clusterfuzz-testcase-minimized-ffmpeg_BSF_VVC_MP4TOANNEXB_fuzzer-4972412487467008
> 
> 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/bsf/vvc_mp4toannexb.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/bsf/vvc_mp4toannexb.c b/libavcodec/bsf/vvc_mp4toannexb.c
> index 25c3726918..a15c1eef5b 100644
> --- a/libavcodec/bsf/vvc_mp4toannexb.c
> +++ b/libavcodec/bsf/vvc_mp4toannexb.c
> @@ -168,8 +168,10 @@ static int vvc_extradata_to_annexb(AVBSFContext *ctx)
>                  goto fail;
>  
>              AV_WB32(new_extradata + new_extradata_size, 1); // add the startcode
> -            bytestream2_get_buffer(&gb, new_extradata + new_extradata_size + 4,
> -                                   nalu_len);
> +            if (bytestream2_get_buffer(&gb, new_extradata + new_extradata_size + 4, nalu_len) != nalu_len) {
> +                ret = AVERROR_INVALIDDATA;
> +                goto fail;
> +            }
>              new_extradata_size += 4 + nalu_len;
>              memset(new_extradata + new_extradata_size, 0,
>                     AV_INPUT_BUFFER_PADDING_SIZE);
> @@ -298,8 +300,10 @@ static int vvc_mp4toannexb_filter(AVBSFContext *ctx, AVPacket *out)
>          if (extra_size)
>              memcpy(out->data + prev_size, ctx->par_out->extradata, extra_size);
>          AV_WB32(out->data + prev_size + extra_size, 1);
> -        bytestream2_get_buffer(&gb, out->data + prev_size + 4 + extra_size,
> -                               nalu_size);
> +        if (bytestream2_get_buffer(&gb, out->data + prev_size + 4 + extra_size, nalu_size) != nalu_size) {
> +            ret = AVERROR_INVALIDDATA;
> +            goto fail;
> +        }
>      }
>  
>      ret = av_packet_copy_props(out, in);

It is better to check that there is enough input before growing the
packet/the extradata. This also allows to use unchecked reads lateron.

- Andreas