samba: Race condition by mount (mount.cifs) operations

client/mount.cifs.c in mount.cifs in smbfs in Samba 3.0.22, 3.0.28a, 3.2.3, 3.3.2, 3.4.0, and 3.4.5 allows local users to mount a CIFS share on an arbitrary mountpoint, and gain privileges, via a symlink attack on the mountpoint directory file...