By using
#if (($is_signed_in) && $permissionChecker.isCompanyAdmin($company_id))
 dockbar()
#end
in portal_normal.vm we can hide access to control panel but any user can access by using http://localhost:8080/group/control_panel url

To avoid it we can restrict access to control panel by using hook.
  1) Into liferay-hook.xml add:
<portal-properties>portal.properties</portal-properties>

Add portal.properties file to hook's src folder and add this line to it:

servlet.service.events.pre=my.event.portal.ControlPanelAccessPreAction

Create ControlPanelAccessPreAction.java into appropriate package and add next code it:

package my.event.portal;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import com.liferay.portal.kernel.events.Action;
import com.liferay.portal.kernel.events.ActionException;
import com.liferay.portal.kernel.util.WebKeys;
import com.liferay.portal.model.User;
import com.liferay.portal.security.auth.PrincipalException;
import com.liferay.portal.service.GroupLocalServiceUtil;
import com.liferay.portal.service.RoleServiceUtil;
import com.liferay.portal.service.UserServiceUtil;
import com.liferay.portal.theme.ThemeDisplay;
 
/**
 * The ControlPanelAccessPreAction restricts access to Control panel of simple
 * users.
 */
public class ControlPanelAccessPreAction extends Action {
 
  /**
   * Instantiates a new control panel access pre action.
   */
  public ControlPanelAccessPreAction() {
 super();
  }
 
  /*
   * @see com.liferay.portal.kernel.events.Action#run(javax.servlet.http. HttpServletRequest,
   * javax.servlet.http.HttpServletResponse)
   */
  public void run(HttpServletRequest request,
      HttpServletResponse response) throws ActionException {
 try {
 
   ThemeDisplay themeDisplay = (ThemeDisplay) request.getAttribute(WebKeys.THEME_DISPLAY);
   if (GroupLocalServiceUtil.getGroup(themeDisplay.getLayout().getGroupId()).isControlPanel()) {
 
  User currentUser = UserServiceUtil.getUserById(themeDisplay.getUserId());
  if (!RoleServiceUtil.hasUserRole(currentUser.getUserId(),
           currentUser.getCompanyId(),
           "administrator",
           true)) {
    throw new PrincipalException("User " + request.getRemoteUser()
     + " can't access the control panel.");
  }
   
   }
 } catch (Exception ex) {
   throw new ActionException(ex);
 }
  }
}