It is a production server - CentOS 6.1
Some user having root access in the past had logged on to the server and removed the SUID bit from the /bin/su file and then exited root. Now we are not able to switch back to root. Also ssh access for root is disabled on the server, so root directly cannot login to the machine. Since we are nor able to su to root nor able to ssh as root we can't set the suid bit for the /bin/su file back.(Also we are not able to switch between users using su)
How it should had been:
$ ll /bin/su -rwsr-xr-x. 1 root root 30092 Mar 10 2011 /bin/su
How it is right now:
$ ll /bin/su -rwxr-xr-x. 1 root root 30092 Mar 10 2011 /bin/su
Is there any way we can switch back to root or set the SUID bit in any way?
Note: We want to avoid a reboot no networking usermode because the server is in use 24x7 and getting downtime is a bit difficult. If reboot was possible then we could simply login using single user mode as root and reset that bit.
Feel free to give creative answers. I can test your answers on our test environment.