wmapro: error out on impossible scale factor offsets

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

libavcodec/wmaprodec.c

@@ -436,7 +436,8 @@ static av_cold int decode_init(AVCodecContext *avctx)
             for (x = 0; x < num_possible_block_sizes; x++) {
                 int v = 0;
                 while (s->sfb_offsets[x][v + 1] << x < offset)
-                    ++v;
+                    if (++v >= MAX_BANDS)
+                        return AVERROR_INVALIDDATA;
                 s->sf_offsets[i][x][b] = v;
             }
         }