[FFmpeg-devel] [PATCH 1/2] avcodec/assdec: undefined use of memcpy()

[Paul B Mahol]

On 7/24/19, Michael Niedermayer <michael at niedermayer.cc> wrote:
> Fixes: null pointer passed as argument 2, which is declared to never be null
> Fixes:
> 16008/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SSA_fuzzer-5650582821404672
> (this is a separate issue found in this testcase)
>
> 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/assdec.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/assdec.c b/libavcodec/assdec.c
> index 3178f2953c..f0b1069cd2 100644
> --- a/libavcodec/assdec.c
> +++ b/libavcodec/assdec.c
> @@ -31,7 +31,8 @@ static av_cold int ass_decode_init(AVCodecContext *avctx)
>      avctx->subtitle_header = av_malloc(avctx->extradata_size + 1);
>      if (!avctx->subtitle_header)
>          return AVERROR(ENOMEM);
> -    memcpy(avctx->subtitle_header, avctx->extradata,
> avctx->extradata_size);
> +    if (avctx->extradata_size)
> +        memcpy(avctx->subtitle_header, avctx->extradata,
> avctx->extradata_size);
>      avctx->subtitle_header[avctx->extradata_size] = 0;
>      avctx->subtitle_header_size = avctx->extradata_size;
>      return 0;
> --
> 2.22.0
>
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i guess it is fine