avformat/iff: check size against INT64_MAX

Bigger sizes are misinterpreted as negative numbers by the API
Fixes: infinite loop
Fixes: 26611/clusterfuzz-testcase-minimized-ffmpeg_dem_IFF_fuzzer-4890614975692800

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit f291cd681b)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/iff.c

@@ -223,6 +223,9 @@ static int parse_dsd_diin(AVFormatContext *s, AVStream *st, uint64_t eof)
         uint64_t orig_pos = avio_tell(pb);
         const char * metadata_tag = NULL;
 
+        if (size >= INT64_MAX)
+            return AVERROR_INVALIDDATA;
+
         switch(tag) {
         case MKTAG('D','I','A','R'): metadata_tag = "artist"; break;
         case MKTAG('D','I','T','I'): metadata_tag = "title";  break;