[FFmpeg-cvslog] avformat/gxf: Check pkt_len

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Mon Oct 26 21:08:55 2020 +0100| [dad9a86ca7bf912289aafb33d96980630e6ec53a] | committer: Michael Niedermayer

avformat/gxf: Check pkt_len

Fixes: Infinite loop
Fixes: 26576/clusterfuzz-testcase-minimized-ffmpeg_dem_GXF_fuzzer-4823080360476672

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=dad9a86ca7bf912289aafb33d96980630e6ec53a
---

 libavformat/gxf.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/libavformat/gxf.c b/libavformat/gxf.c
index 96b7035386..b787d4f521 100644
--- a/libavformat/gxf.c
+++ b/libavformat/gxf.c
@@ -285,9 +285,12 @@ static void gxf_track_tags(AVIOContext *pb, int *len, struct gxf_stream_info *si
 static void gxf_read_index(AVFormatContext *s, int pkt_len) {
     AVIOContext *pb = s->pb;
     AVStream *st;
-    uint32_t fields_per_map = avio_rl32(pb);
-    uint32_t map_cnt = avio_rl32(pb);
+    uint32_t fields_per_map, map_cnt;
     int i;
+    if (pkt_len < 8)
+        return;
+    fields_per_map = avio_rl32(pb);
+    map_cnt = avio_rl32(pb);
     pkt_len -= 8;
     if ((s->flags & AVFMT_FLAG_IGNIDX) || !s->streams) {
         avio_skip(pb, pkt_len);