well , there exists some differents to mount a filesytem if you are a
normal user.
Even if root has added user options in /etc/fstab , user then can
mount the filesytem . But it seems that the setuid program in the
newly mounted FS doesn't a truley setuid program , Even you use ls -
l ,the result like :

[test@localhost mnt]$ ls -l
total 52
-rwsr-sr-x 1 root root 38468 Apr 17 15:47 chmod
drwx------ 2 root root 12288 Apr 17 15:42 lost+found

but the chmod can't turely take efforts on the root's file :p

The OS must be designed to take care of this secure issue.