avcodec/kgv1dec: Check that there is enough input for maximum RLE compression

Fixes: Timeout
Fixes: 4271/clusterfuzz-testcase-4676667768307712

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

libavcodec/kgv1dec.c

@@ -62,6 +62,9 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
     h = (buf[1] + 1) * 8;
     buf += 2;
 
+    if (avpkt->size < 2 + w*h / 513)
+        return AVERROR_INVALIDDATA;
+
     if (w != avctx->width || h != avctx->height) {
         av_freep(&c->frame_buffer);
         av_freep(&c->last_frame_buffer);