From 05f4703a168a336363750e32bcfdd6f303fbdbc3 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Sun, 28 Jan 2018 02:29:00 +0100
Subject: [PATCH] avcodec/mpeg4videodec: Check mb_num also against 0

The spec implies that 0 is invalid in addition to the existing checks

Found-by: <kierank>
Reviewed-by: Kieran Kunhya <kieran618@googlemail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/mpeg4videodec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index 12755b5e8a..ba332de531 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -465,7 +465,7 @@ int ff_mpeg4_decode_video_packet_header(Mpeg4DecContext *ctx)
     }
 
     mb_num = get_bits(&s->gb, mb_num_bits);
-    if (mb_num >= s->mb_num) {
+    if (mb_num >= s->mb_num || !mb_num) {
         av_log(s->avctx, AV_LOG_ERROR,
                "illegal mb_num in video packet (%d %d) \n", mb_num, s->mb_num);
         return -1;