From f935aca44c674d30e3ed940ef73bbad1228a5855 Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Wed, 13 Feb 2013 21:36:25 +0100
Subject: [PATCH] av_memcpy_backptr: avoid an infinite loop for back = 0

CC:libav-stable@libav.org
---
 libavutil/mem.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libavutil/mem.c b/libavutil/mem.c
index 3a4433d154..391eb7db38 100644
--- a/libavutil/mem.c
+++ b/libavutil/mem.c
@@ -252,6 +252,9 @@ static void fill32(uint8_t *dst, int len)
 void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
 {
     const uint8_t *src = &dst[-back];
+    if (!back)
+        return;
+
     if (back == 1) {
         memset(dst, *src, cnt);
     } else if (back == 2) {