[FFmpeg-cvslog] avformat/cafdec: Do not build an index if all packets are the same

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Thu Mar  4 19:21:35 2021 +0100| [ea12590c8ecc1e3c4c7732e5adced21fb5feffa6] | committer: Michael Niedermayer

avformat/cafdec: Do not build an index if all packets are the same

Fixes: Timeout
Fixes: 28214/clusterfuzz-testcase-minimized-ffmpeg_dem_CAF_fuzzer-6495999421579264

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=ea12590c8ecc1e3c4c7732e5adced21fb5feffa6
---

 libavformat/cafdec.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/libavformat/cafdec.c b/libavformat/cafdec.c
index d56187f71f..2a9299d777 100644
--- a/libavformat/cafdec.c
+++ b/libavformat/cafdec.c
@@ -204,15 +204,20 @@ static int read_pakt_chunk(AVFormatContext *s, int64_t size)
     st->nb_frames += avio_rb32(pb); /* priming frames */
     st->nb_frames += avio_rb32(pb); /* remainder frames */
 
-    st->duration = 0;
-    for (i = 0; i < num_packets; i++) {
-        if (avio_feof(pb))
-            return AVERROR_INVALIDDATA;
-        ret = av_add_index_entry(s->streams[0], pos, st->duration, 0, 0, AVINDEX_KEYFRAME);
-        if (ret < 0)
-            return ret;
-        pos += caf->bytes_per_packet ? caf->bytes_per_packet : ff_mp4_read_descr_len(pb);
-        st->duration += caf->frames_per_packet ? caf->frames_per_packet : ff_mp4_read_descr_len(pb);
+    if (caf->bytes_per_packet > 0 && caf->frames_per_packet > 0) {
+        st->duration = caf->frames_per_packet * num_packets;
+        pos          = caf-> bytes_per_packet * num_packets;
+    } else {
+        st->duration = 0;
+        for (i = 0; i < num_packets; i++) {
+            if (avio_feof(pb))
+                return AVERROR_INVALIDDATA;
+            ret = av_add_index_entry(s->streams[0], pos, st->duration, 0, 0, AVINDEX_KEYFRAME);
+            if (ret < 0)
+                return ret;
+            pos += caf->bytes_per_packet ? caf->bytes_per_packet : ff_mp4_read_descr_len(pb);
+            st->duration += caf->frames_per_packet ? caf->frames_per_packet : ff_mp4_read_descr_len(pb);
+        }
     }
 
     if (avio_tell(pb) - ccount > size) {