RHEL 6 : kernel (RHSA-2016:0024)

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 packages that fix two security issues and several bugs
are now available for Red Hat Enterprise Linux 6.6 Extended Update

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

* It was found that the x86 ISA (Instruction Set Architecture) is
prone to a denial of service attack inside a virtualized environment
in the form of an infinite loop in the microcode due to the way
(sequential) delivering of benign exceptions such as #AC (alignment
check exception) and #DB (debug exception) is handled. A privileged
user inside a guest could use these flaws to create denial of service
conditions on the host kernel. (CVE-2015-5307, CVE-2015-8104,

Red Hat would like to thank Ben Serebrin of Google Inc. for reporting
the CVE-2015-5307 issue.

This update also fixes the following bugs :

* When doing TSO/GSO in the presence of VLAN headers on a macvtap
device, the header offsets were incorrectly calculated. As a
consequence, when 2 guests on the same host communicated over a guest
configured VLAN, performance dropped to about 1 Mbps. A set of patches
has been provided to fix this bug, and network performance with VLAN
tags now works with optimal performance. (BZ#1215914)

* Prior to this update, TSO acceleration features have been removed
from the VLAN device which caused that VLAN performance on top of a
virtio device was much lower than that of a virtio device itself. This
update re-enables TSO acceleration features, and performance of VLAN
devices on top of a virtio device has thus been restored. (BZ#1240988)

* With an IPv6 address on a bond and a slave failover, Unsolicited
Neighbor Advertisement (UNA) was previously sent using the link global
IPv6 address as source address. The underlying source code has been
patched, and, after the failover in bonding, UNA is sent using both
the corresponding link IPv6 address and global IPv6 address of bond0
and bond0.vlan. (BZ#1258480)

* Previously, Human Interface Device (HID) would run a report on an
unaligned buffer, which could cause a page fault interrupt and an oops
when the end of the report was read. This update fixes this bug by
padding the end of the report with extra bytes, so the reading of the
report never crosses a page boundary. As a result, a page fault and
subsequent oops no longer occur. (BZ#1268202)

* Inside hugetlb, region data structures were protected by a
combination of a memory map semaphore and a single hugetlb instance
mutex. However, a page-fault scalability improvement backported to the
kernel on previous releases removed the single hugetlb instance mutex
and introduced a new mutex table, making the locking combination
insufficient, leading to possible race windows that could cause
corruption and undefined behavior. The problem could be seen for
example with software mapping or re-mapping hugetlb areas with
concurrent threads reading/writing to same areas causing page faults.
This update fixes the problem by introducing now a required spinlock
to the region tracking functions for proper serialization. The problem
only affects software using huge pages through hugetlb interface.

* Previously, VLAN stacked on the macvlan or macvtap device did not
work for devices that implement and use VLAN filters. As a
consequence, macvtap passthrough mode failed to transfer VLAN packets
over the be2net driver. This update implements VLAN ndo calls to the
macvlan driver to pass appropriate VLAN tag IDs to lower devices. As a
result, macvtap transfers VLAN packets over be2net successfully.

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.

See also :


Solution :

Update the affected packages.

Risk factor :

Medium / CVSS Base Score : 4.9
CVSS Temporal Score : 4.7
Public Exploit Available : true

Family: Red Hat Local Security Checks

Nessus Plugin ID: 87886 ()

Bugtraq ID:

CVE ID: CVE-2015-5307

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