From c54eef46f990722ed65fd1ad1da3d0fc50806eb5 Mon Sep 17 00:00:00 2001
From: Carl Eugen Hoyos <cehoyos@ag.or.at>
Date: Thu, 22 Sep 2016 01:03:55 +0200
Subject: [PATCH] lavc/avpacket: Fix undefined behaviour, do not pass a null
 pointer to memcpy().

Fixes ticket #5857.
---
 libavcodec/avpacket.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libavcodec/avpacket.c b/libavcodec/avpacket.c
index a485064eee..c3f871c347 100644
--- a/libavcodec/avpacket.c
+++ b/libavcodec/avpacket.c
@@ -139,7 +139,8 @@ int av_grow_packet(AVPacket *pkt, int grow_by)
         pkt->buf = av_buffer_alloc(new_size);
         if (!pkt->buf)
             return AVERROR(ENOMEM);
-        memcpy(pkt->buf->data, pkt->data, pkt->size);
+        if (pkt->size > 0)
+            memcpy(pkt->buf->data, pkt->data, pkt->size);
         pkt->data = pkt->buf->data;
     }
     pkt->size += grow_by;