Accidentally ran chmod 775 -R / (not ./) on linux server (RedHat)
If this is a RPM based distribution, you can use the following command to reset permissions to the RPM defaults:
rpm --setperms $(rpm -qa)
It'll at least get you started on the path.
You have backups, right? Hopefully ones that include both files and filesystem metadata? If this happened in my environment, I'd pull last night's backup down to fresh disks and get booted on that. Hope it works out for you!