Log in to Rails app using Facebook SDK
I've implemented a few social apps before.  What you've done is pretty standard practice when it comes to oauth authentication and is secure.

The one thing you could change:

 where(id: fb_user.id).first_or_create do |user|
   user.name = fb_user.name
 end


When you use first_or_create when it creates it'll set the where query as attributes.  So in your case the id will already be set as fb_user.id.