RHSA-2012:1541 - Security Advisory

Topic

Updated kernel packages that fix two security issues and several bugs are
now available for Red Hat Enterprise Linux 6.2 Extended Update Support.

The Red Hat Security Response Team has rated this update as having moderate
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.

Description

These packages contain the Linux kernel.

Security fixes:

• A malicious NFSv4 server could return a crafted reply to a GETACL

request, causing a denial of service on the client. (CVE-2011-4131,
Moderate)

• A flaw in the dl2k driver could allow a local, unprivileged user to issue

potentially harmful IOCTLs, possibly causing Ethernet adapters using the
driver to malfunction (such as losing network connectivity).
(CVE-2012-2313, Low)

Red Hat would like to thank Andy Adamson for reporting CVE-2011-4131, and
Stephan Mueller for reporting CVE-2012-2313.

Bug fixes:

• A kernel oops occurred in the nf_nat code when a bogus pointer was

dereferenced in the nf_conn_nat structure. Consequently, if Source Network
Address Translation (SNAT) was performed, incorrect information could be
received by other CTS (Clear to Send) signals. A conntrack entry is now
placed in the source hash after SNAT has been completed, which prevents the
described problems. (BZ#865715)

• Previously, the ixgbe_setup_tc() function was called recursively when the

set_state() CEE (Convergence Enhanced Ethernet) API routine was called in
IEEE DCBX (Data Center Bridging eXchange) mode. This is considered unsafe
according to the IEEE standards. With this update, the ixgbe driver has
been modified to no longer call the set_state() routine in IEEE DCBX mode.
The driver now calls routines of the PFC (Priority-based Flow Control) and
ETS (Enhanced Transmission Selection) extensions instead of the CEE
extension routines in IEEE DCBX mode. (BZ#867859)

• A Symmetric Multi Processing (SMP) race condition between the munmap()

and exit() function could lead to false-positive triggering of the BUG_ON()
macro if Transparent Huge Pages (THP) were enabled. This update fixes the
race condition, which avoids false-positive triggering of the BUG_ON()
macro in this scenario. (BZ#875121)

• The kernel allows high priority real time tasks, such as tasks scheduled

with the SCHED_FIFO policy, to be throttled. Previously, the CPU stop tasks
were scheduled as high priority real time tasks and could be thus throttled
accordingly. However, the replenishment timer, which is responsible for
clearing a throttle flag on tasks, could be pending on the just disabled
CPU. This could lead to the situation that the throttled tasks were never
scheduled to run. Consequently, if any of such tasks was needed to complete
the CPU disabling, the system became unresponsive. This update introduces a
new scheduler class, which gives a task the highest possible system
priority and such a task cannot be throttled. The stop-task scheduling
class is now used for the CPU stop tasks, and the system shutdown completes
as expected in the scenario described. (BZ#876078)

• Previously, XFS log buffers were handled incorrectly so that XFS could,

in certain circumstances, incorrectly read metadata from the journal during
XFS log recovery. As a consequence, XFS log recovery terminated with an
error message and prevented the file system from being mounted. This
problem could result in a loss of data if the user forcibly emptied the log
to allow the file system to be mounted. This update ensures that metadata
is read correctly from the log and journal recovery thus completes
successfully, and the file system mounts as expected. (BZ#876498)

• Previously, kernel was allowed to reduce the number of unnecessary commit

calls by skipping the commit when there was a large number of outstanding
pages being written. However, a test on the number of commits (ncommit) did
not properly handle the edge case when ncommit was zero. Consequently,
inodes sometimes remained on the sb->s_dirty list and could not be freed by
the inode cache shrinker. As a result, the nfs_inode_cache structure grew
very large over time. With this update, the call to the nfs_write_inode()
function is immediately returned when commit == 0, thus fixing this bug.
(BZ#877394)

Solution

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.

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.2 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.2 i386
• Red Hat Enterprise Linux Server - AUS 6.2 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 6.2 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 6.2 ppc64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.2 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.2 i386
• Red Hat Storage 2.0 x86_64
• Red Hat Gluster Storage Server for On-premise 2.0 x86_64
• Red Hat Storage for Public Cloud (via RHUI) 2.0 x86_64

Fixes

• BZ - 747106 - CVE-2011-4131 kernel: nfs4_getfacl decoding kernel oops
• BZ - 818820 - CVE-2012-2313 kernel: unfiltered netdev rio_ioctl access by users

CVEs

• CVE-2011-4131
• CVE-2012-2313

References

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