aes: Avoid illegal read and don't generate more key than we use.

libavutil/aes.c

@@ -222,11 +222,9 @@ int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
     a->rounds = rounds;
 
     memcpy(tk, key, KC * 4);
+    memcpy(a->round_key[0].u8, key, KC * 4);
 
-    for (t = 0; t < (rounds + 1) * 16;) {
-        memcpy(a->round_key[0].u8 + t, tk, KC * 4);
-        t += KC * 4;
-
+    for (t = KC * 4; t < (rounds + 1) * 16; t += KC * 4) {
         for (i = 0; i < 4; i++)
             tk[0][i] ^= sbox[tk[KC - 1][(i + 1) & 3]];
         tk[0][0] ^= rcon[rconpointer++];
@@ -239,6 +237,8 @@ int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
                 for (i = 0; i < 4; i++)
                     tk[j][i] ^= sbox[tk[j - 1][i]];
         }
+
+        memcpy(a->round_key[0].u8 + t, tk, KC * 4);
     }
 
     if (decrypt) {