RHSA-2012:0107

Problem Description:

Updated kernel packages that fix multiple security issues and two bugs are
now available for Red Hat Enterprise Linux 5.

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.

2. Relevant releases/architectures:

Red Hat Enterprise Linux (v. 5 server) - i386, ia64, noarch, ppc, s390x, x86_64
Red Hat Enterprise Linux Desktop (v. 5 client) - i386, noarch, x86_64

3. Description:

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

This update fixes the following security issues:

* 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 DOC-67874, 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 flaw was found in the Linux kernel in the way splitting two extents in
ext4_ext_convert_to_initialized() worked. A local, unprivileged user with
the ability to mount and unmount ext4 file systems could use this flaw to
cause a denial of service. (CVE-2011-3638, Moderate)

* A flaw was found in the way the Linux kernel's journal_unmap_buffer()
function handled buffer head states. On systems that have an ext4 file
system with a journal mounted, a local, unprivileged user could use this
flaw to cause a denial of service. (CVE-2011-4086, Moderate)

* A divide-by-zero flaw was found in the Linux kernel's igmp_heard_query()
function. An attacker able to send certain IGMP (Internet Group Management
Protocol) packets to a target system could use this flaw to cause a denial
of service. (CVE-2012-0207, Moderate)

Red Hat would like to thank Zheng Liu for reporting CVE-2011-3638, and
Simon McVittie for reporting CVE-2012-0207.

This update also fixes the following bugs:

* When a host was in recovery mode and a SCSI scan operation was initiated,
the scan operation failed and provided no error output. This bug has been
fixed and the SCSI layer now waits for recovery of the host to complete
scan operations for devices. (BZ#772162)

* 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 will simply return an ENOTTY ("Inappropriate
ioctl for device") error and the thread will continue normally. (BZ#773322)

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.

4. 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/kb/docs/DOC-11259

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.

5. Bugs fixed (http://bugzilla.redhat.com/):

747942 - CVE-2011-3638 kernel: ext4: ext4_ext_insert_extent() kernel oops
749143 - CVE-2011-4086 kernel: jbd2: unmapped buffer with _Unwritten or _Delay flags set can lead to DoS
752375 - CVE-2011-4127 kernel: possible privilege escalation via SG_IO ioctl
771764 - CVE-2012-0028 kernel: futex: clear robust_list on execve
772867 - CVE-2012-0207 kernel: igmp: Avoid zero delay when receiving odd mixture of IGMP queries