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

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Date: Tue Sep 20 15:17:10 2005
From: koon at gentoo.org (Thierry Carrez)
Subject: [ GLSA 200509-15 ] util-linux: umount command
	validation error

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Gentoo Linux Security Advisory                           GLSA 200509-15
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                                            http://security.gentoo.org/
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  Severity: High
     Title: util-linux: umount command validation error
      Date: September 20, 2005
      Bugs: #105805
        ID: 200509-15

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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
    -------------------------------------------------------------------
  1  sys-apps/util-linux     < 2.12q-r3                    >= 2.12q-r3

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
==========

  [ 1 ] CAN-2005-2876
        http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=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@...too.org or alternatively, you may file a bug at
http://bugs.gentoo.org.

License
=======

Copyright 2005 Gentoo Foundation, Inc; referenced text
belongs to its owner(s).

The contents of this document are licensed under the
Creative Commons - Attribution / Share Alike license.

http://creativecommons.org/licenses/by-sa/2.0

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