staging: r8188eu: overflow in rtw_p2p_get_go_device_address()

The go_devadd_str[] array is two characters too small to hold the
address so we corrupt memory.

I've changed the user space API slightly and I don't have a way to test
if this breaks anything.  In the original code we truncated away the
last digit of the address and the NUL terminator so it was already a bit
broken.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NLarry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/os_dep/ioctl_linux.c

@@ -3164,9 +3164,7 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
 	u8 *p2pie;
 	uint p2pielen = 0, attr_contentlen = 0;
 	u8 attr_content[100] = {0x00};
-
-	u8 go_devadd_str[17 + 10] = {0x00};
-	/*  +10 is for the str "go_devadd =", we have to clear it at wrqu->data.pointer */
+	u8 go_devadd_str[17 + 12] = {};
 
 	/*	Commented by Albert 20121209 */
 	/*	The input data is the GO's interface address which the application wants to know its device address. */
@@ -3223,12 +3221,12 @@ static int rtw_p2p_get_go_device_address(struct net_device *dev,
 	spin_unlock_bh(&pmlmepriv->scanned_queue.lock);
 
 	if (!blnMatch)
-		sprintf(go_devadd_str, "\n\ndev_add = NULL");
+		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add = NULL");
 	else
-		sprintf(go_devadd_str, "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
+		snprintf(go_devadd_str, sizeof(go_devadd_str), "\n\ndev_add =%.2X:%.2X:%.2X:%.2X:%.2X:%.2X",
 			attr_content[0], attr_content[1], attr_content[2], attr_content[3], attr_content[4], attr_content[5]);
 
-	if (copy_to_user(wrqu->data.pointer, go_devadd_str, 10 + 17))
+	if (copy_to_user(wrqu->data.pointer, go_devadd_str, sizeof(go_devadd_str)))
 		return -EFAULT;
 	return ret;
 }