"An unknown error has occurred" iOS 11.0.1

I just updated to iOS 11.0.1, but when I tried to login to my Apple ID after the installation, I got a message saying "an unknown error has occurred." I can still download apps from the App Store, but I can't see any of my iCloud storage, and iCloud backup is no longer working.

Any idea what might be going on? I'd call support, but I live in South Korea and don't speak Korean, so I couldn't talk to the support people anyway.