[FFmpeg-cvslog] avformat/mov: Disallow empty sidx

[Michael Niedermayer]

ffmpeg | branch: release/3.4 | Michael Niedermayer <michael at niedermayer.cc> | Wed Mar  2 13:01:53 2022 +0100| [b70429e33c7c33eda2f0cbcf8d9fa0752bcd3c22] | committer: Michael Niedermayer

avformat/mov: Disallow empty sidx

It appears this is not allowed "Each Segment Index box documents how a (sub)segment is divided into one or more subsegments
(which may themselves be further subdivided using Segment Index boxes)."
Fixes: Null pointer dereference
Fixes: Ticket9517

Reviewed-by: Paul B Mahol <onemda at gmail.com>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 4419433d77278cb742944c4514be5f72a04103c0)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b70429e33c7c33eda2f0cbcf8d9fa0752bcd3c22
---

 libavformat/mov.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 78ec7e8f45..5bbc54493e 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -4586,7 +4586,7 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     index->track_id = track_id;
 
     index->item_count = avio_rb16(pb);
-    index->items = av_mallocz_array(index->item_count, sizeof(MOVFragmentIndexItem));
+    index->items = index->item_count ? av_mallocz_array(index->item_count, sizeof(MOVFragmentIndexItem)) : NULL;
 
     if (!index->items) {
         av_freep(&index);