From b956373b6f62bfc72b71070b50f1f053225cab8a Mon Sep 17 00:00:00 2001
From: Kostya Shishkov <kostya.shishkov@gmail.com>
Date: Thu, 1 Feb 2007 18:39:49 +0000
Subject: [PATCH] Check for out-of-bounds access

Originally committed as revision 7797 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/vc1.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavcodec/vc1.c b/libavcodec/vc1.c
index 5649484a9f..0c17083039 100644
--- a/libavcodec/vc1.c
+++ b/libavcodec/vc1.c
@@ -2890,8 +2890,8 @@ static int vc1_decode_i_block_adv(VC1Context *v, DCTELEM block[64], int n, int c
         ac_val -= 16 * s->block_wrap[n];
 
     q1 = s->current_picture.qscale_table[mb_pos];
-    if(dc_pred_dir && c_avail) q2 = s->current_picture.qscale_table[mb_pos - 1];
-    if(!dc_pred_dir && a_avail) q2 = s->current_picture.qscale_table[mb_pos - s->mb_stride];
+    if(dc_pred_dir && c_avail && mb_pos) q2 = s->current_picture.qscale_table[mb_pos - 1];
+    if(!dc_pred_dir && a_avail && mb_pos >= s->mb_stride) q2 = s->current_picture.qscale_table[mb_pos - s->mb_stride];
     if(n && n<4) q2 = q1;
 
     if(coded) {