I like all in. Depending on the looseness of the person, maybe a pot size raise or bigger could be correct too. I definitely dont like the idea of putting in a small raise and hopes he'll come over the top. First of all, there's 1 card to a straight on the table, unless he's very very bad at poker, he wont come over the top with an 8, because he'll most likely know if you call a check raise, you'll get an 8 beat, thus if he has an 8 he'll only call. And if a player's that loose, an all in would be the right move even more so, especially that he's passive. Since he showed weakness on the river he wont respect your move as much, in fact if he has an 8 then he'll most likely check call a raise, and if he's loose he'll call an all in often enough. If he doesn't have an 8, he wont call any money worth discussing about. You would then raise a few dollars and hope to get that out of him. An all in raise is most profitable unless you're 100% certain taht an 8 is not in his range.