kernel, perf, python security update

CentOS Errata and Security Advisory CESA-2012:0052

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 permissions were not checked properly in the Linux
  kernel when handling the /proc/[pid]/mem writing functionality. A local,
  unprivileged user could use this flaw to escalate their privileges. Refer
  to Red Hat Knowledgebase article DOC-69129, linked to in the References,
  for further information. (CVE-2012-0056, Important)

Red Hat would like to thank Jüri Aedla for reporting this issue.

This update fixes the following bugs:

• The RHSA-2011:1849 kernel update introduced a bug in the Linux kernel
  scheduler, causing a “WARNING: at kernel/sched.c:5915 thread_return”
  message and a call trace to be logged. This message was harmless, and was
  not due to any system malfunctions or adverse behavior. With this update,
  the WARN_ON_ONCE() call in the scheduler that caused this harmless message
  has been removed. (BZ#768288)

• The RHSA-2011:1530 kernel update introduced a regression in the way
  the Linux kernel maps ELF headers for kernel modules into kernel memory.
  If a third-party kernel module is compiled on a Red Hat Enterprise Linux
  system with a kernel prior to RHSA-2011:1530, then loading that module on
  a system with RHSA-2011:1530 kernel would result in corruption of one byte
  in the memory reserved for the module. In some cases, this could prevent
  the module from functioning correctly. (BZ#769595)

• On some SMP systems the tsc may erroneously be marked as unstable during
  early system boot or while the system is under heavy load. A “Clocksource
  tsc unstable” message was logged when this occurred. As a result the system
  would switch to the slower access, but higher precision HPET clock.

The “tsc=reliable” kernel parameter is supposed to avoid this problem by
indicating that the system has a known good clock, however, the parameter
only affected run time checks. A fix has been put in to avoid the boot
time checks so that the TSC remains as the clock for the duration of
system runtime. (BZ#755867)

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.

Merged security bulletin from advisories:
https://lists.centos.org/pipermail/centos-announce/2012-January/080546.html

Affected packages:
kernel
kernel-debug
kernel-debug-devel
kernel-devel
kernel-doc
kernel-firmware
kernel-headers
perf
python-perf

Upstream details at:
https://access.redhat.com/errata/RHSA-2012:0052