Unfortunately if you have changed files and directories permission to 777 under the all  root  " / ".  You can not reset root password and  logged into user account including graphically.

# cd /

# ls

bin     dev  home  lib64    media  mnt  opt   root  selinux     srv  tmp  var     xen
boot    etc  lib   lost+found     proc  sbin   sys  usr

Solution :

We don't want to be re-install the operating system, can restored all the uids and gids, files and directories permission using  rpm command  with  parameter called --setperms and --setugids .

1. To run the follwing command line reset uids and gids on files and directories,

 #   for i in $(rpm -qa); do rpm --setugids $i; done

2. To run the following command line reset  permissions on files and directories,

 #  for l in $(rpm -qa); do rpm --setperms $l; done

Finally reboot your system,
# reboot