The long road to a fix for CVE-2021-20316

Generally, I think linux is fine adding in (usually default to off) options that break userspace in the name of security (I could be wrong). I think something like this is worth trying out at least to see how much stuff breaks, given it could remove a whole class of toctou bugs.

My userspace was just broken by lack of `/dev/mem` on my fedora box (I was trying to fetch the EDID of my display)