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

http://security.gentoo.org/

Severity:	high
Title:	util-linux: umount command validation error
Date:	09/20/2005
Bugs:	#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	Vulnerable	Unaffected	Architecture(s)
sys-apps/util-linux	< 2.12q-r3	>= 2.12q-r3	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:

    # emerge --sync
    # emerge --ask --oneshot --verbose ">=sys-apps/util-linux-2.12q-r3"

References

CAN-2005-2876

Availability

This GLSA and any updates to it are available for viewing at the Gentoo Security Website: http://security.gentoo.org/glsa/glsa-200509-15.xml

Concerns?

Security is a primary focus of Gentoo Linux and ensuring the confidentiality and security of our users machines is of utmost importance to us. Any security concerns should be addressed to security@gentoo.org or alternatively, you may file a bug at https://bugs.gentoo.org.