huffyuv: pad classic huffman tables so as to avoid bitreader overread.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/huffyuv.c

@@ -85,13 +85,15 @@ typedef struct HYuvContext{
 static const unsigned char classic_shift_luma[] = {
   34,36,35,69,135,232,9,16,10,24,11,23,12,16,13,10,14,8,15,8,
   16,8,17,20,16,10,207,206,205,236,11,8,10,21,9,23,8,8,199,70,
-  69,68, 0
+  69,68, 0,
+  0,0,0,0,0,0,0,0,
 };
 
 static const unsigned char classic_shift_chroma[] = {
   66,36,37,38,39,40,41,75,76,77,110,239,144,81,82,83,84,85,118,183,
   56,57,88,89,56,89,154,57,58,57,26,141,57,56,58,57,58,57,184,119,
-  214,245,116,83,82,49,80,79,78,77,44,75,41,40,39,38,37,36,34, 0
+  214,245,116,83,82,49,80,79,78,77,44,75,41,40,39,38,37,36,34, 0,
+  0,0,0,0,0,0,0,0,
 };
 
 static const unsigned char classic_add_luma[256] = {
@@ -394,10 +396,10 @@ static int read_old_huffman_tables(HYuvContext *s){
     GetBitContext gb;
     int i;
 
-    init_get_bits(&gb, classic_shift_luma, sizeof(classic_shift_luma)*8);
+    init_get_bits(&gb, classic_shift_luma, (sizeof(classic_shift_luma)-8)*8);
     if(read_len_table(s->len[0], &gb)<0)
         return -1;
-    init_get_bits(&gb, classic_shift_chroma, sizeof(classic_shift_chroma)*8);
+    init_get_bits(&gb, classic_shift_chroma, (sizeof(classic_shift_chroma)-8)*8);
     if(read_len_table(s->len[1], &gb)<0)
         return -1;