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Category:   OS (Linux)  >   Linux Kernel Vendors:   kernel.org
(Red Hat Issues Fix for Linux Kernel) Xen Exception Handling Bugs Let Local Users on a Guest System Cause Denial of Service Conditions on the Host System
SecurityTracker Alert ID:  1034421
SecurityTracker URL:  http://securitytracker.com/id/1034421
CVE Reference:   CVE-2015-5307, CVE-2015-8104   (Links to External Site)
Date:  Dec 15 2015
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): RHEL 6.5
Description:   Two vulnerabilities were reported in Xen. A local user on the guest system can cause denial of service conditions on the host system. The Linux Kernel is affected.

The processing of benign exceptions may result in an infinite loop in the CPU. A local user on the guest system can exploit this to cause denial of service conditions on the host system.

An alignment check exception may be triggered by a 32-bit guest [CVE-2015-5307].

A debug exception can be triggered [CVE-2015-8104].

ARM is not affected.

x86 PV VMs are not affected.

x86 CPUs from all manufacturers are affected.

Ben Serebrin from Google and Jan Beulich from SUSE reported these vulnerabilities.

Impact:   A local user on the guest system can cause denial of service conditions on the host system.
Solution:   Red Hat has issued a fix for the Linux Kernel.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2015-2645.html

Vendor URL:  rhn.redhat.com/errata/RHSA-2015-2645.html (Links to External Site)
Cause:   Exception handling error

Message History:   This archive entry is a follow-up to the message listed below.
Nov 10 2015 Xen Exception Handling Bugs Let Local Users on a Guest System Cause Denial of Service Conditions on the Host System



 Source Message Contents

Subject:  [RHSA-2015:2645-01] Important: kernel security and bug fix update

-----BEGIN PGP SIGNED MESSAGE-----
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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Important: kernel security and bug fix update
Advisory ID:       RHSA-2015:2645-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2015-2645.html
Issue date:        2015-12-15
CVE Names:         CVE-2015-5307 CVE-2015-8104 
=====================================================================

1. Summary:

Updated kernel packages that fix two security issues and two bugs are now
available for Red Hat Enterprise Linux 6.5 Advanced Update Support.

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.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Server AUS (v. 6.5) - i386, noarch, ppc64, s390x, x86_64
Red Hat Enterprise Linux Server Optional AUS (v. 6.5) - i386, ppc64, s390x, x86_64

3. Description:

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, Important)

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:

* 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#1258479)

* 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#1268201)

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.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

5. Bugs fixed (https://bugzilla.redhat.com/):

1277172 - CVE-2015-5307 virt: guest to host DoS by triggering an infinite loop in microcode via #AC exception
1278496 - CVE-2015-8104 virt: guest to host DoS by triggering an infinite loop in microcode via #DB exception

6. Package List:

Red Hat Enterprise Linux Server AUS (v. 6.5):

Source:
kernel-2.6.32-431.68.1.el6.src.rpm

i386:
kernel-2.6.32-431.68.1.el6.i686.rpm
kernel-debug-2.6.32-431.68.1.el6.i686.rpm
kernel-debug-debuginfo-2.6.32-431.68.1.el6.i686.rpm
kernel-debug-devel-2.6.32-431.68.1.el6.i686.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.i686.rpm
kernel-debuginfo-common-i686-2.6.32-431.68.1.el6.i686.rpm
kernel-devel-2.6.32-431.68.1.el6.i686.rpm
kernel-headers-2.6.32-431.68.1.el6.i686.rpm
perf-2.6.32-431.68.1.el6.i686.rpm
perf-debuginfo-2.6.32-431.68.1.el6.i686.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.i686.rpm

noarch:
kernel-abi-whitelists-2.6.32-431.68.1.el6.noarch.rpm
kernel-doc-2.6.32-431.68.1.el6.noarch.rpm
kernel-firmware-2.6.32-431.68.1.el6.noarch.rpm

ppc64:
kernel-2.6.32-431.68.1.el6.ppc64.rpm
kernel-bootwrapper-2.6.32-431.68.1.el6.ppc64.rpm
kernel-debug-2.6.32-431.68.1.el6.ppc64.rpm
kernel-debug-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm
kernel-debug-devel-2.6.32-431.68.1.el6.ppc64.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm
kernel-debuginfo-common-ppc64-2.6.32-431.68.1.el6.ppc64.rpm
kernel-devel-2.6.32-431.68.1.el6.ppc64.rpm
kernel-headers-2.6.32-431.68.1.el6.ppc64.rpm
perf-2.6.32-431.68.1.el6.ppc64.rpm
perf-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm

s390x:
kernel-2.6.32-431.68.1.el6.s390x.rpm
kernel-debug-2.6.32-431.68.1.el6.s390x.rpm
kernel-debug-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
kernel-debug-devel-2.6.32-431.68.1.el6.s390x.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
kernel-debuginfo-common-s390x-2.6.32-431.68.1.el6.s390x.rpm
kernel-devel-2.6.32-431.68.1.el6.s390x.rpm
kernel-headers-2.6.32-431.68.1.el6.s390x.rpm
kernel-kdump-2.6.32-431.68.1.el6.s390x.rpm
kernel-kdump-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
kernel-kdump-devel-2.6.32-431.68.1.el6.s390x.rpm
perf-2.6.32-431.68.1.el6.s390x.rpm
perf-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.s390x.rpm

x86_64:
kernel-2.6.32-431.68.1.el6.x86_64.rpm
kernel-debug-2.6.32-431.68.1.el6.x86_64.rpm
kernel-debug-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm
kernel-debug-devel-2.6.32-431.68.1.el6.x86_64.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm
kernel-debuginfo-common-x86_64-2.6.32-431.68.1.el6.x86_64.rpm
kernel-devel-2.6.32-431.68.1.el6.x86_64.rpm
kernel-headers-2.6.32-431.68.1.el6.x86_64.rpm
perf-2.6.32-431.68.1.el6.x86_64.rpm
perf-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm

Red Hat Enterprise Linux Server Optional AUS (v. 6.5):

Source:
kernel-2.6.32-431.68.1.el6.src.rpm

i386:
kernel-debug-debuginfo-2.6.32-431.68.1.el6.i686.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.i686.rpm
kernel-debuginfo-common-i686-2.6.32-431.68.1.el6.i686.rpm
perf-debuginfo-2.6.32-431.68.1.el6.i686.rpm
python-perf-2.6.32-431.68.1.el6.i686.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.i686.rpm

ppc64:
kernel-debug-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm
kernel-debuginfo-common-ppc64-2.6.32-431.68.1.el6.ppc64.rpm
perf-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm
python-perf-2.6.32-431.68.1.el6.ppc64.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.ppc64.rpm

s390x:
kernel-debug-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
kernel-debuginfo-common-s390x-2.6.32-431.68.1.el6.s390x.rpm
kernel-kdump-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
perf-debuginfo-2.6.32-431.68.1.el6.s390x.rpm
python-perf-2.6.32-431.68.1.el6.s390x.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.s390x.rpm

x86_64:
kernel-debug-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm
kernel-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm
kernel-debuginfo-common-x86_64-2.6.32-431.68.1.el6.x86_64.rpm
perf-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm
python-perf-2.6.32-431.68.1.el6.x86_64.rpm
python-perf-debuginfo-2.6.32-431.68.1.el6.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/

7. References:

https://access.redhat.com/security/cve/CVE-2015-5307
https://access.redhat.com/security/cve/CVE-2015-8104
https://access.redhat.com/security/updates/classification/#important

8. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2015 Red Hat, Inc.
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