avformat/oggparsevorbis: check packet size before reading new_len from it

Fixes out of array read
Fixes: 34260c7981118fb38fba61809bf4dd5a-asan_heap-oob_93b923_1508_cov_951051643_DivX640x480_oggvorbis.avi
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/oggparsevorbis.c

@@ -347,7 +347,7 @@ static int vorbis_header(AVFormatContext *s, int idx)
             avpriv_set_pts_info(st, 64, 1, srate);
         }
     } else if (os->buf[os->pstart] == 3) {
-        if (vorbis_update_metadata(s, idx) >= 0) {
+        if (vorbis_update_metadata(s, idx) >= 0 && priv->len[1] > 10) {
             // drop all metadata we parsed and which is not required by libvorbis
             unsigned new_len = 7 + 4 + AV_RL32(priv->packet[1] + 7) + 4 + 1;
             if (new_len >= 16 && new_len < os->psize) {