For ichidan verbs, potential form is made by changing the ru to rareru. The same is done to change them to passive.

e.g taberu -> taberareru (can eat; also, be eaten)

For yodan verbs, potential is made by ending with eru and potential by areru.

e.g korosu -> koroseru (can kill) korosu -> korosareru (be killed)

Now how does one make a potential passive i.e "can be eaten" or "can be killed"?