For everyone running a kernel >= 5.8, or a distro kernel that has BPF_PROG_TYPE_LSM backported, I have developed a mitigation that does not require a reboot whatsoever:

https://github.com/Jannik2099/copyfail-ebpf-mitigation

Note that this does not fix any already manipulated page cache entries, it only denies new attempts to use authencesn