Gentoo: GDM Local Denial of Service
Posted by Benjamin D. Thomas   
Gentoo A local user could send a crafted message to /tmp/.gdm_socket that would trigger the null pointer dereference and crash GDM, thus preventing it from managing future displays.
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Gentoo Linux Security Advisory                           GLSA 200709-11
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                                            http://security.gentoo.org/
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  Severity: Low
     Title: GDM: Local Denial of Service
      Date: September 18, 2007
      Bugs: #187919
        ID: 200709-11

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Synopsis
========

GDM can be crashed by a local user, preventing it from managing future
displays.

Background
==========

GDM is the GNOME display manager.

Affected packages
=================

    -------------------------------------------------------------------
     Package         /  Vulnerable  /                       Unaffected
    -------------------------------------------------------------------
  1  gnome-base/gdm      < 2.18.4                            >= 2.18.4
                                                            *>= 2.16.7

Description
===========

The result of a g_strsplit() call is incorrectly parsed in the files
daemon/gdm.c, daemon/gdmconfig.c, gui/gdmconfig.c and
gui/gdmflexiserver.c, allowing for a null pointer dereference.

Impact
======

A local user could send a crafted message to /tmp/.gdm_socket that
would trigger the null pointer dereference and crash GDM, thus
preventing it from managing future displays.

Workaround
==========

Restrict the write permissions on /tmp/.gdm_socket to trusted users
only after each GDM restart.

Resolution
==========

All GDM users should upgrade to the latest version:

    # emerge --sync
    # emerge --ask --oneshot --verbose "gnome-base/gdm"

References
==========

  [ 1 ] CVE-2007-3381
        http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-3381

Availability
============

This GLSA and any updates to it are available for viewing at
the Gentoo Security Website:

  http://security.gentoo.org/glsa/glsa-200709-11.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
http://bugs.gentoo.org.

License
=======

Copyright 2007 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/2.5