Can't login. Kick back to Login page

When I input user name, password then click Login, It will kick me back to Login page without saying any error message. I checked nginx-error.log and it says about permission denial in file inside /usr/local/hestia/data/sessions. if I change sessions directory permission to 777, it works. if I change to 770, it doesn’t. Should I leave permission to 777? Is it safe? It happens after I apt upgrade yesterday.