Race condition in the ecryptfs_mount function in fs/ecryptfs/main.c in the
eCryptfs subsystem in the Linux kernel before 3.1 allows local users to
bypass intended file permissions via a mount.ecryptfs_private mount with a
mismatched uid.

Vasiliy Kulikov and Dan Rosenberg discovered that ecryptfs did not
correctly check the origin of mount points. A local attacker could exploit
this to trick the system into unmounting arbitrary mount points, leading to
a denial of service.