[FFmpeg-devel] [PATCH 1/4] avformat/asfdec_o: Check size vs. offset in detect_unknown_subobject()

[Michael Niedermayer]

Fixes: signed integer overflow: 2314885530818453566 + 7503032301549264928 cannot be represented in type 'long'
Fixes: 26639/clusterfuzz-testcase-minimized-ffmpeg_dem_ASF_O_fuzzer-6024222100684800

Alternatively this could be ignored but then the end condition of the loop
would be hard to reach as avio_tell() is int64_t

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
---
 libavformat/asfdec_o.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libavformat/asfdec_o.c b/libavformat/asfdec_o.c
index 655ba9f9ef..6ce5a3fb43 100644
--- a/libavformat/asfdec_o.c
+++ b/libavformat/asfdec_o.c
@@ -1661,6 +1661,9 @@ static int detect_unknown_subobject(AVFormatContext *s, int64_t offset, int64_t
     ff_asf_guid guid;
     int ret;
 
+    if (offset > INT64_MAX - size)
+        return AVERROR_INVALIDDATA;
+
     while (avio_tell(pb) <= offset + size) {
         if (avio_tell(pb) == asf->offset)
             break;
-- 
2.17.1