RHSA-2012:1087 - Security Advisory

Topic

Updated kernel packages that fix one security issue and multiple 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. 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

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

This update fixes the following security issue:

• It was found that the data_len parameter of the sock_alloc_send_pskb()

function in the Linux kernel's networking implementation was not validated
before use. A local user with access to a TUN/TAP virtual interface could
use this flaw to crash the system or, potentially, escalate their
privileges. Note that unprivileged users cannot access TUN/TAP devices
until the root user grants them access. (CVE-2012-2136, Important)

This update also fixes the following bugs:

• An insufficiently designed calculation in the CPU accelerator in the

previous kernel caused an arithmetic overflow in the sched_clock() function
when system uptime exceeded 208.5 days. This overflow led to a kernel panic
on the systems using the Time Stamp Counter (TSC) or Virtual Machine
Interface (VMI) clock source. This update corrects the described
calculation so that this arithmetic overflow and kernel panic can no longer
occur under these circumstances. (BZ#825981, BZ#835449)

• Previously, a race condition between the journal_write_metadata_buffer()

and jbd_unlock_bh_state() functions could occur. Consequently, another
thread could call the get_write_access() function on the buffer head and
cause the wrong data to be written into the journal. If the system
terminated unexpectedly or was shut down incorrectly, subsequent file
system journal replay could result in file system corruption. This update
fixes the race condition and the file system corruption no longer occurs in
the described scenario. (BZ#833764)

• When the kvmclock initialization was used in a guest, it could write to

the Time Stamp Counter (TSC) and, under certain circumstances, could cause
the kernel to become unresponsive on boot. With this update, TSC
synchronization, which is unnecessary due to kvmclock, has been disabled,
thus fixing this bug. (BZ#834557)

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.

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

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 5.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.6 ia64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.6 i386
• Red Hat Enterprise Linux Server - AUS 5.6 x86_64
• Red Hat Enterprise Linux Server - AUS 5.6 ia64
• Red Hat Enterprise Linux Server - AUS 5.6 i386
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 5.6 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 5.6 ppc
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 5.6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 5.6 i386

Fixes

• BZ - 816289 - CVE-2012-2136 kernel: net: insufficient data_len validation in sock_alloc_send_pskb()

CVEs

• CVE-2012-2136

References

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