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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:  1034917
SecurityTracker URL:  http://securitytracker.com/id/1034917
CVE Reference:   CVE-2015-8104   (Links to External Site)
Date:  Feb 3 2016
Impact:   Denial of service via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): RHEL 7.1
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 CVE-2015-8104.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2016-0103.html

Vendor URL:  rhn.redhat.com/errata/RHSA-2016-0103.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-2016:0103-01] Important: kernel security, bug fix, and enhancement update

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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Important: kernel security, bug fix, and enhancement update
Advisory ID:       RHSA-2016:0103-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2016-0103.html
Issue date:        2016-02-02
CVE Names:         CVE-2015-8104 CVE-2016-0728 CVE-2016-0774 
=====================================================================

1. Summary:

Updated kernel packages that fix three security issues, multiple bugs, and
one enhancement are now available for Red Hat Enterprise Linux 7.1 Extended
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 ComputeNode EUS (v. 7.1) - noarch, x86_64
Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.1) - x86_64
Red Hat Enterprise Linux Server EUS (v. 7.1) - noarch, ppc64, ppc64le, s390x, x86_64
Red Hat Enterprise Linux Server Optional EUS (v. 7.1) - ppc64, ppc64le, 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 #DB (debug exception) is handled. A privileged
user inside a guest could use this flaw to create denial of service
conditions on the host kernel. (CVE-2015-8104, Important)

* A use-after-free flaw was found in the way the Linux kernel's key
management subsystem handled keyring object reference counting in certain
error path of the join_session_keyring() function. A local, unprivileged
user could use this flaw to escalate their privileges on the system.
(CVE-2016-0728, Important)

* It was found that the fix for CVE-2015-1805 incorrectly kept buffer
offset and buffer length in sync on a failed atomic read, potentially
resulting in a pipe buffer state corruption. A local, unprivileged user
could use this flaw to crash the system or leak kernel memory to user
space. (CVE-2016-0774, Moderate)

Red Hat would like to thank the Perception Point research team for
reporting the CVE-2016-0728 issue. The security impact of the CVE-2016-0774
issue was discovered by Red Hat.

Bug fixes:

* NMI watchdog of guests using legacy LVT0-based NMI delivery did not work
with APICv. Now, NMI works with LVT0 regardless of APICv. (BZ#1244726)

* Parallel file-extending direct I/O writes could previously race to update
the size of the file. If they executed out-of-order, the file size could
move backwards and push a previously completed write beyond the end of the
file, causing it to be lost. (BZ#1258942)

* The GHES NMI handler had a global spin lock that significantly increased
the latency of each perf sample collection. This update simplifies locking
inside the handler. (BZ#1280200)

* Sometimes, iptables rules are updated along with ip rules, and routes are
reloaded. Previously, skb->sk was mistakenly attached to some IPv6
forwarding traffic packets, which could cause kernel panic. Now, such
packets are checked and not processed. (BZ#1281700)

* The NUMA node was not reported for PCI adapters, which affected every
POWER system deployed with Red Hat Enterprise Linux 7 and caused
significant decrease in the system performance. (BZ#1283525)

* Processing packets with a lot of different IPv6 source addresses caused
the kernel to return warnings concerning soft-lockups due to high lock
contention and latency increase. (BZ#1285369)

* Running edge triggered interrupts with an ack notifier when
simultaneously reconfiguring the Intel I/O IOAPIC did not work correctly,
so EOI in the interrupt did not cause a VM to exit if APICv was enabled.
Consequently, the VM sometimes became unresponsive. (BZ#1287001)

* Block device readahead was artificially limited, so the read performance
was poor, especially on RAID devices. Now, per-device readahead limits are
used for each device, which has improved read performance. (BZ#1287548)

* Identical expectations could not be tracked simultaneously even if they
resided in different connection tracking zones. Now, an expectation insert
attempt is rejected only if the zone is also identical. (BZ#1290093)

* The storvsc kernel driver for Microsoft Hyper-V storage was setting
incorrect SRB flags, and Red Hat Enterprise Linux 7 guests running on
Microsoft Hyper-V were experiencing slow I/O as well as I/O failures when
they were connected to a virtual SAN. Now, SRB flags are set correctly.
(BZ#1290095)

* When a NUMA system with no memory in node 0 was used, the system
terminated unexpectedly during boot or when using OpenVSwitch. Now, the
kernel tries to allocate memory from other nodes when node 0 is not
present. (BZ#1300950)

Enhancement:

* IPsec has been updated to provide many fixes and some enhancements.
Of particular note is the ability to match on outgoing interfaces.
(BZ#1287407)

4. Solution:

All kernel users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues and add this
enhancement. The system must be rebooted for this update to take effect.

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/):

1278496 - CVE-2015-8104 virt: guest to host DoS by triggering an infinite loop in microcode via #DB exception
1297475 - CVE-2016-0728 kernel: Possible use-after-free vulnerability in keyring facility
1303961 - CVE-2016-0774 kernel: pipe buffer state corruption after unsuccessful atomic read from pipe

6. Package List:

Red Hat Enterprise Linux ComputeNode EUS (v. 7.1):

Source:
kernel-3.10.0-229.26.2.el7.src.rpm

noarch:
kernel-abi-whitelists-3.10.0-229.26.2.el7.noarch.rpm
kernel-doc-3.10.0-229.26.2.el7.noarch.rpm

x86_64:
kernel-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debug-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debug-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debug-devel-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.26.2.el7.x86_64.rpm
kernel-devel-3.10.0-229.26.2.el7.x86_64.rpm
kernel-headers-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-libs-3.10.0-229.26.2.el7.x86_64.rpm
perf-3.10.0-229.26.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm

Red Hat Enterprise Linux ComputeNode Optional EUS (v. 7.1):

x86_64:
kernel-debug-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-libs-devel-3.10.0-229.26.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
python-perf-3.10.0-229.26.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm

Red Hat Enterprise Linux Server EUS (v. 7.1):

Source:
kernel-3.10.0-229.26.2.el7.src.rpm

noarch:
kernel-abi-whitelists-3.10.0-229.26.2.el7.noarch.rpm
kernel-doc-3.10.0-229.26.2.el7.noarch.rpm

ppc64:
kernel-3.10.0-229.26.2.el7.ppc64.rpm
kernel-bootwrapper-3.10.0-229.26.2.el7.ppc64.rpm
kernel-debug-3.10.0-229.26.2.el7.ppc64.rpm
kernel-debug-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
kernel-debug-devel-3.10.0-229.26.2.el7.ppc64.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
kernel-debuginfo-common-ppc64-3.10.0-229.26.2.el7.ppc64.rpm
kernel-devel-3.10.0-229.26.2.el7.ppc64.rpm
kernel-headers-3.10.0-229.26.2.el7.ppc64.rpm
kernel-tools-3.10.0-229.26.2.el7.ppc64.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
kernel-tools-libs-3.10.0-229.26.2.el7.ppc64.rpm
perf-3.10.0-229.26.2.el7.ppc64.rpm
perf-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm

s390x:
kernel-3.10.0-229.26.2.el7.s390x.rpm
kernel-debug-3.10.0-229.26.2.el7.s390x.rpm
kernel-debug-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
kernel-debug-devel-3.10.0-229.26.2.el7.s390x.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
kernel-debuginfo-common-s390x-3.10.0-229.26.2.el7.s390x.rpm
kernel-devel-3.10.0-229.26.2.el7.s390x.rpm
kernel-headers-3.10.0-229.26.2.el7.s390x.rpm
kernel-kdump-3.10.0-229.26.2.el7.s390x.rpm
kernel-kdump-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
kernel-kdump-devel-3.10.0-229.26.2.el7.s390x.rpm
perf-3.10.0-229.26.2.el7.s390x.rpm
perf-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.s390x.rpm

x86_64:
kernel-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debug-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debug-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debug-devel-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.26.2.el7.x86_64.rpm
kernel-devel-3.10.0-229.26.2.el7.x86_64.rpm
kernel-headers-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-libs-3.10.0-229.26.2.el7.x86_64.rpm
perf-3.10.0-229.26.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm

Red Hat Enterprise Linux Server EUS (v. 7.1):

Source:
kernel-3.10.0-229.26.2.ael7b.src.rpm

noarch:
kernel-abi-whitelists-3.10.0-229.26.2.ael7b.noarch.rpm
kernel-doc-3.10.0-229.26.2.ael7b.noarch.rpm

ppc64le:
kernel-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-bootwrapper-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-debug-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-debug-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-debuginfo-common-ppc64le-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-devel-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-headers-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-tools-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-tools-libs-3.10.0-229.26.2.ael7b.ppc64le.rpm
perf-3.10.0-229.26.2.ael7b.ppc64le.rpm
perf-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
python-perf-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm

Red Hat Enterprise Linux Server Optional EUS (v. 7.1):

ppc64:
kernel-debug-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
kernel-debuginfo-common-ppc64-3.10.0-229.26.2.el7.ppc64.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
kernel-tools-libs-devel-3.10.0-229.26.2.el7.ppc64.rpm
perf-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm
python-perf-3.10.0-229.26.2.el7.ppc64.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.ppc64.rpm

s390x:
kernel-debug-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
kernel-debuginfo-common-s390x-3.10.0-229.26.2.el7.s390x.rpm
kernel-kdump-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
perf-debuginfo-3.10.0-229.26.2.el7.s390x.rpm
python-perf-3.10.0-229.26.2.el7.s390x.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.s390x.rpm

x86_64:
kernel-debug-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
kernel-tools-libs-devel-3.10.0-229.26.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm
python-perf-3.10.0-229.26.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.26.2.el7.x86_64.rpm

Red Hat Enterprise Linux Server Optional EUS (v. 7.1):

ppc64le:
kernel-debug-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-debug-devel-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-debuginfo-common-ppc64le-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-tools-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
kernel-tools-libs-devel-3.10.0-229.26.2.ael7b.ppc64le.rpm
perf-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.rpm
python-perf-3.10.0-229.26.2.ael7b.ppc64le.rpm
python-perf-debuginfo-3.10.0-229.26.2.ael7b.ppc64le.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-2015-8104
https://access.redhat.com/security/cve/CVE-2016-0728
https://access.redhat.com/security/cve/CVE-2016-0774
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 2016 Red Hat, Inc.
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