cavsdec: check run value validity

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

libavcodec/cavsdec.c

@@ -125,6 +125,8 @@ static int decode_residual_block(AVSContext *h, GetBitContext *gb,
         level_code = get_ue_code(gb,r->golomb_order);
         if(level_code >= ESCAPE_CODE) {
             run = ((level_code - ESCAPE_CODE) >> 1) + 1;
+            if(run > 64)
+                return -1;
             esc_code = get_ue_code(gb,esc_golomb_order);
             level = esc_code + (run > r->max_run ? 1 : r->level_add[run]);
             while(level > r->inc_limit)