From 4419433d77278cb742944c4514be5f72a04103c0 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Wed, 2 Mar 2022 13:01:53 +0100
Subject: [PATCH] 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@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/mov.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libavformat/mov.c b/libavformat/mov.c
index 5e26267810..68b6d7f075 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -5118,6 +5118,8 @@ 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;