wavpack: validate samples size parsed in wavpack_decode_block

Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavcodec/wavpack.c

@@ -796,6 +796,9 @@ static int wavpack_decode_block(AVCodecContext *avctx, int block_no,
     if (!wc->mkv_mode) {
         s->samples = AV_RL32(buf);
         buf       += 4;
+        if (s->samples != wc->samples)
+            return AVERROR_INVALIDDATA;
+
         if (!s->samples) {
             *got_frame_ptr = 0;
             return 0;