Joined: 12 May 2004
|Posted: Tue Sep 20, 2005 2:31 pm Post subject: [ GLSA 200509-15 ] util-linux: umount command validation err
|Gentoo Linux Security Advisory
Title: util-linux: umount command validation error (GLSA 200509-15)
Date: September 20, 2005
A command validation error in umount can lead to an escalation of privileges.
util-linux is a suite of useful Linux programs including umount, a program used to unmount filesystems.
Vulnerable: < 2.12q-r3
Unaffected: >= 2.12q-r3
Architectures: All supported architectures
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.
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.
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.
All util-linux users should upgrade to the latest version:
|# emerge --sync
# emerge --ask --oneshot --verbose ">=sys-apps/util-linux-2.12q-r3"
Last edited by GLSA on Sun May 07, 2006 4:58 pm; edited 1 time in total