avcodec/snow: Fix av_malloc* failure checks

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/snow.c

@@ -594,11 +594,18 @@ static int halfpel_interpol(SnowContext *s, uint8_t *halfpel[4][4], AVFrame *fra
         int ls= frame->linesize[p];
         uint8_t *src= frame->data[p];
 
-        halfpel[1][p] = (uint8_t*) av_malloc_array(ls, (h + 2 * EDGE_WIDTH)) + EDGE_WIDTH * (1 + ls);
-        halfpel[2][p] = (uint8_t*) av_malloc_array(ls, (h + 2 * EDGE_WIDTH)) + EDGE_WIDTH * (1 + ls);
-        halfpel[3][p] = (uint8_t*) av_malloc_array(ls, (h + 2 * EDGE_WIDTH)) + EDGE_WIDTH * (1 + ls);
-        if (!halfpel[1][p] || !halfpel[2][p] || !halfpel[3][p])
+        halfpel[1][p] = av_malloc_array(ls, (h + 2 * EDGE_WIDTH));
+        halfpel[2][p] = av_malloc_array(ls, (h + 2 * EDGE_WIDTH));
+        halfpel[3][p] = av_malloc_array(ls, (h + 2 * EDGE_WIDTH));
+        if (!halfpel[1][p] || !halfpel[2][p] || !halfpel[3][p]) {
+            av_freep(&halfpel[1][p]);
+            av_freep(&halfpel[2][p]);
+            av_freep(&halfpel[3][p]);
             return AVERROR(ENOMEM);
+        }
+        halfpel[1][p] += EDGE_WIDTH * (1 + ls);
+        halfpel[2][p] += EDGE_WIDTH * (1 + ls);
+        halfpel[3][p] += EDGE_WIDTH * (1 + ls);
 
         halfpel[0][p]= src;
         for(y=0; y<h; y++){