RHEL 6 : kernel-rt (RHSA-2016:0224)

This script is Copyright (C) 2016-2017 Tenable Network Security, Inc.


Synopsis :

The remote Red Hat host is missing one or more security updates.

Description :

Updated kernel-rt packages that fix two security issues, several bugs,
and add various enhancements are now available for Red Hat Enterprise
MRG 2.5.

Red Hat Product Security 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.

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

* It was found that the Linux kernel's keys subsystem did not
correctly garbage collect uninstantiated keyrings. A local attacker
could use this flaw to crash the system or, potentially, escalate
their privileges on the system. (CVE-2015-7872, Important)

* A flaw was found in the way the Linux kernel handled IRET faults
during the processing of NMIs. An unprivileged, local user could use
this flaw to crash the system or, potentially (although highly
unlikely), escalate their privileges on the system. (CVE-2015-5157,
Moderate)

This update provides a build of the kernel-rt package for Red Hat
Enterprise MRG 2.5 that is layered on Red Hat Enterprise Linux 6, and
provides a number of bug fixes and enhancements, including :

* [md] dm: fix AB-BA deadlock in __dm_destroy()

* [md] revert 'dm-mpath: fix stalls when handling invalid ioctl

* [cpufreq] intel_pstate: Fix limits->max_perf and
limits->max_policy_pct rounding errors

* [cpufreq] revert 'intel_pstate: fix rounding error in max_freq_pct'

* [crypto] nx: 842 - Add CRC and validation support

* [of] return NUMA_NO_NODE from fallback of_node_to_nid()

(BZ#1277670)

The HP Smart Array (hpsa) SCSI driver has been updated to the latest
version included in a Red Hat release. (BZ#1224096)

This update also fixes the following bugs :

* A heavy load of incoming packets on a fast networking driver (like
the i40e) will both stress the softirq mechanism on the realtime
kernel (as described in BZ#1293229) and exercise the possible livelock
in the netpoll NAPI/busy polling routines (as described in
BZ#1293230). The fixes applied to both BZ#1293229 and BZ#1293230 will
address these issues by hardening the locking mechanism for the
netpoll NAPI/busy polling and by enhancing the way softirqs are
serviced. These fixes also create a failsafe to avoiding RCU stalls on
a heavily loaded system and allows the networking driver to work as
expected. (BZ#1200766)

* The nohz_full code in older versions of the MRG-Realtime kernels was
incomplete and known to be problematic due to the way the old
implementation interacted with the real time features in the kernel.
The nohz_full kernel code has been updated enabling this feature to
function as expected and allowing this feature to be enabled in the
realtime kernel. (BZ#1278511)

* Because the realtime kernel replaces most of the spinlocks with
rtmutexes, the locking scheme used in both NAPI polling and busy
polling could become out of synchronization with the State Machine
they protected. This could cause system performance degradation or
even a livelock situation when a machine with faster NICs (10g or 40g)
was subject to a heavy pressure receiving network packets. The locking
schemes on NAPI polling and busy polling routines were hardened to
enforce the State machine sanity to help ensure the system continues
to function properly under pressure. (BZ#1295884)

* A possible livelock in the NAPI polling and busy polling routines
could lead the system to a livelock on threads running at high,
realtime, priorities. The threads running at priorities lower than the
ones of the threads involved in the livelock would be prevented from
running on the CPUs affected by the livelock. Among those lower
priority threads are the rcuc/ threads. Right before (4 jiffies) a RCU
stall is detected, the rcuc/ threads on the CPUs facing the livelock
have their priorities boosted above the priority of the threads
involved in the livelock. The softirq code was also updated to be more
robust. These modifications allowed the rcuc/ threads to execute even
under system pressure, mitigating the RCU stalls. (BZ#1295885)

All kernel-rt users are advised to upgrade to these updated packages,
which correct these issues and add these enhancements. The system must
be rebooted for this update to take effect.

See also :

https://www.redhat.com/security/data/cve/CVE-2015-5157.html
https://www.redhat.com/security/data/cve/CVE-2015-7872.html
http://rhn.redhat.com/errata/RHSA-2016-0224.html

Solution :

Update the affected packages.

Risk factor :

High / CVSS Base Score : 7.2
(CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:C)
CVSS Temporal Score : 5.3
(CVSS2#E:U/RL:OF/RC:C)
Public Exploit Available : false

Family: Red Hat Local Security Checks

Nessus Plugin ID: 88792 ()

Bugtraq ID:

CVE ID: CVE-2015-5157
CVE-2015-7872

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