RHSA-2013:1519 - 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
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.

Description

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

• A race condition was found in the way asynchronous I/O and fallocate()

interacted when using the ext4 file system. A local, unprivileged user
could use this flaw to expose random data from an extent whose data blocks
have not yet been written, and thus contain data from a deleted file.
(CVE-2012-4508, Important)

• An information leak flaw was found in the way Linux kernel's device

mapper subsystem, under certain conditions, interpreted data written to
snapshot block devices. An attacker could use this flaw to read data from
disk blocks in free space, which are normally inaccessible. (CVE-2013-4299,
Moderate)

Red Hat would like to thank Theodore Ts'o for reporting CVE-2012-4508, and
Fujitsu for reporting CVE-2013-4299. Upstream acknowledges Dmitry Monakhov
as the original reporter of CVE-2012-4508.

This update also fixes the following bugs:

• When the Audit subsystem was under heavy load, it could loop infinitely

in the audit_log_start() function instead of failing over to the error
recovery code. This would cause soft lockups in the kernel. With this
update, the timeout condition in the audit_log_start() function has been
modified to properly fail over when necessary. (BZ#1017898)

• When handling Memory Type Range Registers (MTRRs), the

stop_one_cpu_nowait() function could potentially be executed in parallel
with the stop_machine() function, which resulted in a deadlock. The MTRR
handling logic now uses the stop_machine() function and makes use of mutual
exclusion to avoid the aforementioned deadlock. (BZ#1017902)

• Power-limit notification interrupts were enabled by default. This could

lead to degradation of system performance or even render the system
unusable on certain platforms, such as Dell PowerEdge servers. Power-limit
notification interrupts have been disabled by default and a new kernel
command line parameter "int_pln_enable" has been added to allow users to
observe these events using the existing system counters. Power-limit
notification messages are also no longer displayed on the console.
The affected platforms no longer suffer from degraded system performance
due to this problem. (BZ#1020519)

• Package level thermal and power limit events are not defined as MCE

errors for the x86 architecture. However, the mcelog utility erroneously
reported these events as MCE errors with the following message:

kernel: [Hardware Error]: Machine check events logged

Package level thermal and power limit events are no longer reported as MCE
errors by mcelog. When these events are triggered, they are now reported
only in the respective counters in sysfs (specifically,
/sys/devices/system/cpu/cpu<number>/thermal_throttle/). (BZ#1021950)

• An insufficiently designed calculation in the CPU accelerator could cause

an arithmetic overflow in the set_cyc2ns_scale() function if the system
uptime exceeded 208 days prior to using kexec to boot into a new kernel.
This overflow led to a kernel panic on systems using the Time Stamp Counter
(TSC) clock source, primarily systems using Intel Xeon E5 processors that
do not reset TSC on soft power cycles. A patch has been applied to modify
the calculation so that this arithmetic overflow and kernel panic can no
longer occur under these circumstances. (BZ#1024453)

All kernel users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues. The system must be
rebooted 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/site/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
• Red Hat Enterprise Linux EUS Compute Node 6.2 x86_64

Fixes

• BZ - 869904 - CVE-2012-4508 kernel: ext4: AIO vs fallocate stale data exposure
• BZ - 1004233 - CVE-2013-4299 kernel: dm: dm-snapshot data leak

CVEs

• CVE-2012-4508
• CVE-2013-4299

References

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