avformat/iff: Check size before skip

Fixes: Infinite loop
Fixes: 27292/clusterfuzz-testcase-minimized-ffmpeg_dem_IFF_fuzzer-5731168991051776

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

libavformat/iff.c

@@ -259,6 +259,9 @@ static int parse_dsd_prop(AVFormatContext *s, AVStream *st, uint64_t eof)
         uint64_t size     = avio_rb64(pb);
         uint64_t orig_pos = avio_tell(pb);
 
+        if (size >= INT64_MAX)
+            return AVERROR_INVALIDDATA;
+
         switch(tag) {
         case MKTAG('A','B','S','S'):
             if (size < 8)