avformat/cafdec: Check that data chunk end fits within 64bit

Fixes: signed integer overflow: 64 + 9223372036854775803 cannot be represented in type 'long long'
Fixes: 51896/clusterfuzz-testcase-minimized-ffmpeg_dem_CAF_fuzzer-6536881135550464
Fixes: 62276/clusterfuzz-testcase-minimized-ffmpeg_dem_CAF_fuzzer-6536881135550464

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

libavformat/cafdec.c

@@ -343,6 +343,9 @@ static int read_header(AVFormatContext *s)
             avio_skip(pb, 4); /* edit count */
             caf->data_start = avio_tell(pb);
             caf->data_size  = size < 0 ? -1 : size - 4;
+            if (caf->data_start < 0 || caf->data_size > INT64_MAX - caf->data_start)
+                return AVERROR_INVALIDDATA;
+
             if (caf->data_size > 0 && (pb->seekable & AVIO_SEEKABLE_NORMAL))
                 avio_skip(pb, caf->data_size);
             found_data = 1;