RHEL 7 : kernel-rt (RHSA-2016:0212)

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
Linux 7.

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,

The kernel-rt packages have been upgraded to version 3.10.0-327.10.1,
which 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()


This update also fixes the following bugs :

* 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 have been hardened
to enforce the State machine sanity to help ensure the system
continues to function properly under pressure. (BZ#1293230)

* 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 were prevented from
running on the CPUs affected by the livelock. Among those lower
priority threads are the rcuc/ threads. With this update, 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 has also
been updated to be more robust. These modifications allow the rcuc/
threads to execute even under system pressure, mitigating the RCU
stalls. (BZ#1293229)

* Multiple CPUs trying to take an rq lock previously caused large
latencies on machines with many CPUs. On systems with more than 32
cores, this update uses the 'push' rather than 'pull' approach and
provides multiple changes to the scheduling of rq locks. As a result,
machines no longer suffer from multiplied latencies on large CPU
systems. (BZ#1282597)

* Previously, the SFC driver for 10 GB cards executed polling in NAPI
mode, using a locking mechanism similar to a 'trylock'. Consequently,
when running on a Realtime kernel, a livelock could occur. This update
modifies the locking mechanism so that once the lock is taken it is
not released until the operation is complete. (BZ#1282609)

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 :


Solution :

Update the affected packages.

Risk factor :

High / CVSS Base Score : 7.2
CVSS Temporal Score : 5.3
Public Exploit Available : false

Family: Red Hat Local Security Checks

Nessus Plugin ID: 88791 ()

Bugtraq ID:

CVE ID: CVE-2015-5157

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