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

[Michael Niedermayer]

ffmpeg | branch: release/4.1 | Michael Niedermayer <michael at niedermayer.cc> | Wed Mar  2 13:01:53 2022 +0100| [5a67ee57970b198d0417af30ca8a21ca6cd98d38] | 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=5a67ee57970b198d0417af30ca8a21ca6cd98d38
---

 libavformat/mov.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 67dcbd5b7a..24c85e43bb 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -5041,6 +5041,8 @@ static int mov_read_sidx(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     avio_rb16(pb); // reserved
 
     item_count = avio_rb16(pb);
+    if (item_count == 0)
+        return AVERROR_INVALIDDATA;
 
     for (i = 0; i < item_count; i++) {
         int index;