avcodec/s302menc: check if buf_size can actually be put into 16bit size

This disallows creating unplayable audio.
Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavcodec/s302menc.c

@@ -78,6 +78,11 @@ static int s302m_encode2_frame(AVCodecContext *avctx, AVPacket *avpkt,
     uint8_t *o;
     PutBitContext pb;
 
+    if (buf_size - AES3_HEADER_LEN > UINT16_MAX) {
+        av_log(avctx, AV_LOG_ERROR, "number of samples in frame too big\n");
+        return AVERROR(EINVAL);
+    }
+
     if ((ret = ff_alloc_packet2(avctx, avpkt, buf_size, 0)) < 0)
         return ret;