cavs: Check for negative cbp

Sample-Id: 00000647-google
Reported-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavcodec/cavsdec.c

@@ -602,8 +602,8 @@ static inline int decode_residual_inter(AVSContext *h)
 
     /* get coded block pattern */
     int cbp = get_ue_golomb(&h->gb);
-    if (cbp > 63) {
-        av_log(h->avctx, AV_LOG_ERROR, "illegal inter cbp\n");
+    if (cbp > 63 || cbp < 0) {
+        av_log(h->avctx, AV_LOG_ERROR, "illegal inter cbp %d\n", cbp);
         return AVERROR_INVALIDDATA;
     }
     h->cbp = cbp_tab[cbp][1];
@@ -673,7 +673,7 @@ static int decode_mb_i(AVSContext *h, int cbp_code)
     /* get coded block pattern */
     if (h->cur.f->pict_type == AV_PICTURE_TYPE_I)
         cbp_code = get_ue_golomb(gb);
-    if (cbp_code > 63) {
+    if (cbp_code > 63 || cbp_code < 0) {
         av_log(h->avctx, AV_LOG_ERROR, "illegal intra cbp\n");
         return AVERROR_INVALIDDATA;
     }