[FFmpeg-cvslog] avformat/id3v2: Check end for overflow in id3v2_parse()

[Michael Niedermayer]

ffmpeg | branch: release/4.4 | Michael Niedermayer <michael at niedermayer.cc> | Mon Apr 19 20:23:44 2021 +0200| [6f83f6de0446e02f66c0d2a5f7cd950797d26681] | committer: Michael Niedermayer

avformat/id3v2: Check end for overflow in id3v2_parse()

Fixes: signed integer overflow: 9223372036840103978 + 67637280 cannot be represented in type 'long'
Fixes: 33341/clusterfuzz-testcase-minimized-ffmpeg_dem_DSF_fuzzer-6408154041679872

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit efdb56450418933965dc6e27f0b1625d25e44a8c)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=6f83f6de0446e02f66c0d2a5f7cd950797d26681
---

 libavformat/id3v2.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
index f33b7ba93a..1377cef4b8 100644
--- a/libavformat/id3v2.c
+++ b/libavformat/id3v2.c
@@ -816,7 +816,7 @@ static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
     int isv34, unsync;
     unsigned tlen;
     char tag[5];
-    int64_t next, end = avio_tell(pb) + len;
+    int64_t next, end = avio_tell(pb);
     int taghdrlen;
     const char *reason = NULL;
     AVIOContext pb_local;
@@ -828,6 +828,10 @@ static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
     av_unused int uncompressed_buffer_size = 0;
     const char *comm_frame;
 
+    if (end > INT64_MAX - len - 10)
+        return;
+    end += len;
+
     av_log(s, AV_LOG_DEBUG, "id3v2 ver:%d flags:%02X len:%d\n", version, flags, len);
 
     switch (version) {