[ GLSA 200509-15 ] util-linux: umount command validation error

[GLSA]

Gentoo Linux Security Advisory

Title: util-linux: umount command validation error (GLSA 200509-15)
Severity: high
Exploitable: local
Date: September 20, 2005
Bug(s): #105805
ID: 200509-15

Synopsis


A command validation error in umount can lead to an escalation of
privileges.


Background


util-linux is a suite of useful Linux programs including umount, a
program used to unmount filesystems.


Affected Packages

Package: sys-apps/util-linux
Vulnerable: < 2.12q-r3
Unaffected: >= 2.12q-r3
Architectures: All supported architectures


Description


When a regular user mounts a filesystem, they are subject to
restrictions in the /etc/fstab configuration file. David Watson
discovered that when unmounting a filesystem with the '-r' option, the
read-only bit is set, while other bits, such as nosuid or nodev, are
not set, even if they were previously.


Impact


An unprivileged user facing nosuid or nodev restrictions can
umount -r a filesystem clearing those bits, allowing applications to be
executed suid, or have device nodes interpreted. In the case where the
user can freely modify the contents of the filesystem, privilege
escalation may occur as a custom program may execute with suid
permissions.


Workaround


Two workarounds exist, first, the suid bit can be removed from the
umount utility, or users can be restricted from mounting and unmounting
filesystems in /etc/fstab.


Resolution


All util-linux users should upgrade to the latest version: