[FFmpeg-cvslog] avformat/id3v2: Sanity check tlen before alloc and uncompress

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sat Nov  7 21:39:21 2020 +0100| [d7f87a4b9ef18a9846439b7787874cc11e5940de] | committer: Michael Niedermayer

avformat/id3v2: Sanity check tlen before alloc and uncompress

Fixes: Timeout (>20sec -> 65ms)
Fixes: 26896/clusterfuzz-testcase-minimized-ffmpeg_dem_DAUD_fuzzer-5691024049176576
Fixes: 27627/clusterfuzz-testcase-minimized-ffmpeg_dem_AEA_fuzzer-4907019324358656

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=d7f87a4b9ef18a9846439b7787874cc11e5940de
---

 libavformat/id3v2.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libavformat/id3v2.c b/libavformat/id3v2.c
index cecd9b9f6d..336a3964de 100644
--- a/libavformat/id3v2.c
+++ b/libavformat/id3v2.c
@@ -993,6 +993,9 @@ static void id3v2_parse(AVIOContext *pb, AVDictionary **metadata,
 
                     av_log(s, AV_LOG_DEBUG, "Compresssed frame %s tlen=%d dlen=%ld\n", tag, tlen, dlen);
 
+                    if (tlen <= 0)
+                        goto seek;
+
                     av_fast_malloc(&uncompressed_buffer, &uncompressed_buffer_size, dlen);
                     if (!uncompressed_buffer) {
                         av_log(s, AV_LOG_ERROR, "Failed to alloc %ld bytes\n", dlen);