[FFmpeg-devel] [PATCH] avcodec/pngdec: Check input space

[Kieran Kunhya]

On Tue, 14 May 2019 at 20:42, Michael Niedermayer <michael at niedermayer.cc>
wrote:

> Fixes: Timeout (33sec -> 78ms)
> Fixes:
> 14668/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_LSCR_fuzzer-5767073352908800
>
> Found-by: continuous fuzzing process
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by
> <https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by>:
> Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/pngdec.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
> index 6a681be29d..78988d9e75 100644
> --- a/libavcodec/pngdec.c
> +++ b/libavcodec/pngdec.c
> @@ -1535,6 +1535,9 @@ static int decode_frame_lscr(AVCodecContext *avctx,
>      AVFrame *frame = data;
>      int ret, nb_blocks, offset = 0;
>
> +    if (avpkt->size < 2)
> +        return AVERROR_INVALIDDATA;
> +
>

Why not 1?
Or maybe 3?
Or maybe 42?

Random numbers to fix random samples are just absurd.

Kieran