avcodec/ffwavesynth: Check if there is enough extradata before allocation

Fixes: OOM
Fixes: 15750/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FFWAVESYNTH_fuzzer-5702090367696896

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/ffwavesynth.c

@@ -247,7 +247,7 @@ static int wavesynth_parse_extradata(AVCodecContext *avc)
     edata_end = edata + avc->extradata_size;
     ws->nb_inter = AV_RL32(edata);
     edata += 4;
-    if (ws->nb_inter < 0)
+    if (ws->nb_inter < 0 || (edata_end - edata) / 24 < ws->nb_inter)
         return AVERROR(EINVAL);
     ws->inter = av_calloc(ws->nb_inter, sizeof(*ws->inter));
     if (!ws->inter)