Check for out-of-bounds access

Originally committed as revision 7797 to svn://svn.ffmpeg.org/ffmpeg/trunk
18 years ago · b956373b6f
parent 286c71074a
commit b956373b6f
1 changed files with 2 additions and 2 deletions
--- 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) {