If iwd, or cryptsetup with certain non-default algorithms, isn't being used on the system, you should be fine. Not many programs use AF_ALG. It's possible there are others I'm not aware of, but it's quite rare.

To be clear, general-purpose Linux distros generally can't disable these kconfig options yet, due to these cases. But there are many Linux systems that simply don't need this functionality.

A good project for someone to work on would be to fix iwd and cryptsetup to always use userspace crypto, as they should.

I can’t comment on the ramifications, except to note that elsewhere in the thread this appears to not break anything (whether it makes userspace crypto a little less safe is academic, but that doesn’t matter if we have an easy local root shell), but I can verify the above fix does protect Ubuntu 24.04 from the exploit.

Just reboot after applying this change.

Or

  zgrep CONFIG_CRYPTO_USER_API /proc/config.gz

Is it built as a module in most distros?