Important: kernel security and bug fix update

Updated kernel packages that fix several security issues and various bugs
are now available for Red Hat Enterprise Linux 5.6 Extended Update Support.

The Red Hat Security Response Team has rated this update as having
important security impact. Common Vulnerability Scoring System (CVSS) base
scores, which give detailed severity ratings, are available for each
vulnerability from the CVE links in the References section.

The kernel packages contain the Linux kernel, the core of any Linux
operating system.

This update fixes the following security issues:

* Using PCI passthrough without interrupt remapping support allowed Xen
hypervisor guests to generate MSI interrupts and thus potentially inject
traps. A privileged guest user could use this flaw to crash the host or
possibly escalate their privileges on the host. The fix for this issue can
prevent PCI passthrough working and guests starting. Refer to Red Hat
Bugzilla bug 715555 for details. (CVE-2011-1898, Important)

* IPv6 fragment identification value generation could allow a remote
attacker to disrupt a target system's networking, preventing legitimate
users from accessing its services. (CVE-2011-2699, Important)

* Using the SG_IO ioctl to issue SCSI requests to partitions or LVM volumes
resulted in the requests being passed to the underlying block device. If a
privileged user only had access to a single partition or LVM volume, they
could use this flaw to bypass those restrictions and gain read and write
access (and be able to issue other SCSI commands) to the entire block
device. Refer to Red Hat Knowledgebase article 67869, linked to in the
References, for further details about this issue. (CVE-2011-4127,
Important)

* A flaw was found in the way the Linux kernel handled robust list pointers
of user-space held futexes across exec() calls. A local, unprivileged user
could use this flaw to cause a denial of service or, eventually, escalate
their privileges. (CVE-2012-0028, Important)

* A missing boundary check was found in the Linux kernel's HFS file system
implementation. A local attacker could use this flaw to cause a denial of
service or escalate their privileges by mounting a specially-crafted disk.
(CVE-2011-4330, Moderate)

Red Hat would like to thank Fernando Gont for reporting CVE-2011-2699, and
Clement Lecigne for reporting CVE-2011-4330.

This update also fixes the following bugs:

* Previously, all timers for a Xen fully-virtualized domain were based on
the time stamp counter (TSC) of the underlying physical CPU. This could
cause observed time to go backwards on some hosts. This update moves all
timers except HPET to the Xen monotonic system time, which fixes the bug as
long as the HPET is removed from the configuration of the domain.
(BZ#773359)

* Previously, tests of the Microsoft Server Virtualization Validation
Program (SVVP) detected unreliability of the emulated HPET (High
Performance Event Timer) on some hosts. Now, HPET can be configured as a
per-domain configuration option; if it is disabled, the guest chooses a
more reliable timer source. Disabling HPET is suggested for Windows guests,
as well as fully-virtualized Linux guests that show occasional "time went
backwards" errors in the console. (BZ#773360)

* SG_IO ioctls were not implemented correctly in the Red Hat Enterprise
Linux 5 virtio-blk driver. Sending an SG_IO ioctl request to a virtio-blk
disk caused the sending thread to enter an uninterruptible sleep state ("D"
state). With this update, SG_IO ioctls are rejected by the virtio-blk
driver; the ioctl system call simply returns an ENOTTY ("Inappropriate
ioctl for device") error and the thread continues normally. (BZ#784658)

Users should upgrade to these updated packages, which contain backported
patches to correct these issues. The system must be rebooted for this
update to take effect.

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

To install kernel packages manually, use "rpm -ivh [package]". Do not
use "rpm -Uvh" as that will remove the running kernel binaries from
your system. You may use "rpm -e" to remove old kernels after
determining that the new kernel functions properly on your system.

715555 - CVE-2011-1898 virt: VT-d (PCI passthrough) MSI trap injection
723429 - CVE-2011-2699 kernel: ipv6: make fragment identifications less predictable
752375 - CVE-2011-4127 kernel: possible privilege escalation via SG_IO ioctl
755431 - CVE-2011-4330 kernel: hfs: add sanity check for file name length
771764 - CVE-2012-0028 kernel: futex: clear robust_list on execve
773360 - provide option to disable HPET [rhel-5.6.z]
784658 - Install RHEV-H to virtual machine cause VM kernel panic when boot [rhel-5.6.z]

https://www.redhat.com/security/data/cve/CVE-2011-1898.html
https://www.redhat.com/security/data/cve/CVE-2011-2699.html
https://www.redhat.com/security/data/cve/CVE-2011-4127.html
https://www.redhat.com/security/data/cve/CVE-2011-4330.html
https://www.redhat.com/security/data/cve/CVE-2012-0028.html
https://access.redhat.com/security/updates/classification/#important
https://access.redhat.com/knowledge/articles/66747
https://bugzilla.redhat.com/show_bug.cgi?id=715555
https://access.redhat.com/knowledge/articles/67869