avformat/id3v2: Check avio_read() return code in id3v2_parse()

Fixes use of uninitialized memory
Fixes: msan_uninit-mem_7f5a04a9b50d_7087_mp3__mp3__tooSmallFinal.mp3
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/id3v2.c

@@ -667,7 +667,8 @@ static void id3v2_parse(AVFormatContext *s, int len, uint8_t version,
         unsigned long dlen;
 
         if (isv34) {
-            avio_read(s->pb, tag, 4);
+            if (avio_read(s->pb, tag, 4) < 0)
+                break;
             tag[4] = 0;
             if (version == 3) {
                 tlen = avio_rb32(s->pb);
@@ -676,7 +677,8 @@ static void id3v2_parse(AVFormatContext *s, int len, uint8_t version,
             tflags  = avio_rb16(s->pb);
             tunsync = tflags & ID3v2_FLAG_UNSYNCH;
         } else {
-            avio_read(s->pb, tag, 3);
+            if (avio_read(s->pb, tag, 3) < 0)
+                break;
             tag[3] = 0;
             tlen   = avio_rb24(s->pb);
         }