avformat/id3v2: Check end for overflow in id3v2_parse()

Fixes: signed integer overflow: 9223372036840103978 + 67637280 cannot be represented in type 'long'
Fixes: 33341/clusterfuzz-testcase-minimized-ffmpeg_dem_DSF_fuzzer-6408154041679872

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

libavformat/id3v2.c

@@ -824,7 +824,7 @@ static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
     int isv34, unsync;
     unsigned tlen;
     char tag[5];
-    int64_t next, end = avio_tell(pb) + len;
+    int64_t next, end = avio_tell(pb);
     int taghdrlen;
     const char *reason = NULL;
     AVIOContext pb_local;
@@ -836,6 +836,10 @@ static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
     av_unused int uncompressed_buffer_size = 0;
     const char *comm_frame;
 
+    if (end > INT64_MAX - len - 10)
+        return;
+    end += len;
+
     av_log(s, AV_LOG_DEBUG, "id3v2 ver:%d flags:%02X len:%d\n", version, flags, len);
 
     switch (version) {