[FFmpeg-cvslog] avformat/asfdec_o: Check size vs. offset in detect_unknown_subobject()

Michael Niedermayer git at videolan.org
Wed Jan 20 22:35:18 EET 2021


ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Tue Jan 12 21:17:18 2021 +0100| [0bee216ad454dd7238a03dd9a76428cc6c3233cc] | committer: Michael Niedermayer

avformat/asfdec_o: Check size vs. offset in detect_unknown_subobject()

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>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=0bee216ad454dd7238a03dd9a76428cc6c3233cc
---

 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;



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