rndis_wlan: add range check in del_key()

Wifi drivers can have up to 6 keys but the rndis_wlan only has 4 so
it needs to have its own checks to make sure we don't go out of
bounds.  The add_key() function already checks but I added some
checks to del_key() and set_default_key().
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rndis_wlan.c

@@ -414,6 +414,7 @@ struct ndis_80211_pmkid {
 #define RNDIS_WLAN_ALG_TKIP	(1<<1)
 #define RNDIS_WLAN_ALG_CCMP	(1<<2)
 
+#define RNDIS_WLAN_NUM_KEYS		4
 #define RNDIS_WLAN_KEY_MGMT_NONE	0
 #define RNDIS_WLAN_KEY_MGMT_802_1X	(1<<0)
 #define RNDIS_WLAN_KEY_MGMT_PSK		(1<<1)
@@ -516,7 +517,7 @@ struct rndis_wlan_private {
 
 	/* encryption stuff */
 	int  encr_tx_key_index;
-	struct rndis_wlan_encr_key encr_keys[4];
+	struct rndis_wlan_encr_key encr_keys[RNDIS_WLAN_NUM_KEYS];
 	int  wpa_version;
 
 	u8 command_buffer[COMMAND_BUFFER_SIZE];
@@ -1535,6 +1536,9 @@ static int remove_key(struct usbnet *usbdev, int index, const u8 *bssid)
 	bool is_wpa;
 	int ret;
 
+	if (index >= RNDIS_WLAN_NUM_KEYS)
+		return -ENOENT;
+
 	if (priv->encr_keys[index].len == 0)
 		return 0;
 
@@ -2451,6 +2455,9 @@ static int rndis_set_default_key(struct wiphy *wiphy, struct net_device *netdev,
 
 	netdev_dbg(usbdev->net, "%s(%i)\n", __func__, key_index);
 
+	if (key_index >= RNDIS_WLAN_NUM_KEYS)
+		return -ENOENT;
+
 	priv->encr_tx_key_index = key_index;
 
 	if (is_wpa_key(priv, key_index))