RHSA-2013:0896 - Security Advisory

Topic

Updated qemu-kvm packages that fix one security issue and two bugs are now
available for Red Hat Enterprise Linux 6.

The Red Hat Security Response Team has rated this update as having moderate
security impact. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available from the CVE link in
the References section.

Description

KVM (Kernel-based Virtual Machine) is a full virtualization solution for
Linux on AMD64 and Intel 64 systems. qemu-kvm is the user-space component
for running virtual machines using KVM.

It was found that QEMU Guest Agent (the "qemu-ga" service) created
certain files with world-writable permissions when run in daemon mode
(the default mode). An unprivileged guest user could use this flaw to
consume all free space on the partition containing the qemu-ga log file, or
modify the contents of the log. When a UNIX domain socket transport was
explicitly configured to be used (not the default), an unprivileged guest
user could potentially use this flaw to escalate their privileges in the
guest. This update requires manual action. Refer below for details.
(CVE-2013-2007)

This update does not change the permissions of the existing log file or
the UNIX domain socket. For these to be changed, stop the qemu-ga service,
and then manually remove all "group" and "other" permissions on the
affected files, or remove the files.

Note that after installing this update, files created by the
guest-file-open QEMU Monitor Protocol (QMP) command will still continue to
be created with world-writable permissions for backwards compatibility.

This issue was discovered by Laszlo Ersek of Red Hat.

This update also fixes the following bugs:

• Previously, due to integer overflow in code calculations, the qemu-kvm

utility was reporting incorrect memory size on QMP events when using the
virtio balloon driver with more than 4 GB of memory. This update fixes the
overflow in the code and qemu-kvm works as expected in the described
scenario. (BZ#958750)

• When the set_link flag is set to "off" to change the status of a network

card, the status is changed to "down" on the respective guest. Previously,
with certain network cards, when such a guest was restarted, the status of
the network card was unexpectedly reset to "up", even though the network
was unavailable. A patch has been provided to address this bug and the link
status change is now preserved across restarts for all network cards.
(BZ#927591)

All users of qemu-kvm should upgrade to these updated packages, which
contain backported patches to correct these issues. After installing this
update, shut down all running virtual machines. Once all virtual machines
have shut down, start them again for this update to take effect.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.4 i386
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.4 x86_64
• Red Hat Gluster Storage Server for On-premise 2.1 x86_64
• Red Hat Enterprise Linux Server - AUS 6.4 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.4 i386
• Red Hat Storage for Public Cloud (via RHUI) 2.1 x86_64

Fixes

• BZ - 927591 - use set_link to change rtl8139 and e1000 network card's status but fail to make effectively after reboot guest
• BZ - 956082 - CVE-2013-2007 qemu: guest agent creates files with insecure permissions in deamon mode

CVEs

• CVE-2013-2007

References

• https://access.redhat.com/security/updates/classification/#moderate