I am using 'smbmount' to mount a Windows file system on a directory in $HOME on my Linux box. This works for a user if smbmount is SUID.
However I don't seem to be able to umount the file system except as root, it just says:- umount: /home/chris/win is not in the fstab (and you are not root)
The umount executable is alread SUID but this doesn't seem to help.