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Category:   OS (Linux)  >   Linux Kernel Vendors:   kernel.org
(Red Hat Issues Fix for the 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:  1034373
SecurityTracker URL:  http://securitytracker.com/id/1034373
CVE Reference:   CVE-2015-5307   (Links to External Site)
Date:  Dec 10 2015
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-2015-5307 for the Linux Kernel.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2015-2587.html

Vendor URL:  rhn.redhat.com/errata/RHSA-2015-2587.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-2015:2587-01] Important: kernel security, bug fix, and enhancement update

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

Synopsis:          Important: kernel security, bug fix, and enhancement update
Advisory ID:       RHSA-2015:2587-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2015-2587.html
Issue date:        2015-12-09
CVE Names:         CVE-2015-2925 CVE-2015-5307 CVE-2015-7613 
=====================================================================

1. Summary:

Updated kernel packages that fix three security issues, several 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, s390x, x86_64
Red Hat Enterprise Linux Server Optional EUS (v. 7.1) - ppc64, s390x, x86_64

3. Description:

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

* A flaw was found in the way the Linux kernel's file system implementation
handled rename operations in which the source was inside and the
destination was outside of a bind mount. A privileged user inside a
container could use this flaw to escape the bind mount and, potentially,
escalate their privileges on the system. (CVE-2015-2925, Important)

* 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) is handled.
A privileged user inside a guest could use this flaw to create denial of
service conditions on the host kernel. (CVE-2015-5307, Important)

* A race condition flaw was found in the way the Linux kernel's IPC
subsystem initialized certain fields in an IPC object structure that were
later used for permission checking before inserting the object into a
globally visible list. A local, unprivileged user could potentially use
this flaw to elevate their privileges on the system. (CVE-2015-7613,
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 and adds one enhancement:

* When setting up an ESP IPsec connection, the aes_ctr algorithm did not
work for ESP on a Power little endian VM host. As a consequence, a kernel
error was previously returned and the connection failed to be established.
A set of patches has been provided to fix this bug, and aes_ctr works for
ESP in the described situation as expected. (BZ#1247127)

* The redistribute3() function distributed entries across 3 nodes. However,
some entries were moved an incorrect way, breaking the ordering. As a
result, BUG() in the dm-btree-remove.c:shift() function occurred when
entries were removed from the btree. A patch has been provided to fix this
bug, and redistribute3() now works as expected. (BZ#1263945)

* When booting an mpt2sas adapter in a huge DDW enabled slot on Power, the
kernel previously generated a warning followed by a call trace.
The provided patch set enhances the Power kernel to be able to support
IOMMU as a fallback for the cases where the coherent mask of the device is
not suitable for direct DMA. As a result, neither the warning nor the call
trace occur in this scenario. (BZ#1267133)

* If the client mounted /exports and tried to execute the "chown -R"
command across the entire mountpoint, a warning about a circular directory
structure was previously returned because mount points all had the same
inode number. A set of patches has been provided to fix this bug, and mount
points are now assigned with unique inode numbers as expected. (BZ#1273239)

* Due to a validation error of in-kernel MMIO tracing, a VM became
previously unresponsive when connected to Red Hat Enterprise Virtualization
Hypervisor. The provided patch fixes this bug by dropping the check in MMIO
handler, and a VM continues running as expected. (BZ#1275149)

* The NFS client could previously fail to send a CLOSE operation if the
file was opened with O_WRONLY and the server restarted after the OPEN.
Consequently, the server appeared in a state that could block other NFS
operations from completing. The client's state flags have been modified to
catch this condition and correctly CLOSE the file. (BZ#1275298)

* This update sets multicast filters for multicast packets when the
interface is not in promiscuous mode. This change has an impact on the RAR
usage such that SR-IOV has some RARs reserved for its own usage as well.
(BZ#1265091)

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.

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/):

1209367 - CVE-2015-2925 Kernel: vfs: Do not allow escaping from bind mounts
1268270 - CVE-2015-7613 kernel: Unauthorized access to IPC objects with SysV shm
1277172 - CVE-2015-5307 virt: guest to host DoS by triggering an infinite loop in microcode via #AC exception

6. Package List:

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

Source:
kernel-3.10.0-229.24.2.el7.src.rpm

noarch:
kernel-abi-whitelists-3.10.0-229.24.2.el7.noarch.rpm
kernel-doc-3.10.0-229.24.2.el7.noarch.rpm

x86_64:
kernel-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debug-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debug-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debug-devel-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.24.2.el7.x86_64.rpm
kernel-devel-3.10.0-229.24.2.el7.x86_64.rpm
kernel-headers-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-libs-3.10.0-229.24.2.el7.x86_64.rpm
perf-3.10.0-229.24.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm

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

x86_64:
kernel-debug-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-libs-devel-3.10.0-229.24.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
python-perf-3.10.0-229.24.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm

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

Source:
kernel-3.10.0-229.24.2.el7.src.rpm

noarch:
kernel-abi-whitelists-3.10.0-229.24.2.el7.noarch.rpm
kernel-doc-3.10.0-229.24.2.el7.noarch.rpm

ppc64:
kernel-3.10.0-229.24.2.el7.ppc64.rpm
kernel-bootwrapper-3.10.0-229.24.2.el7.ppc64.rpm
kernel-debug-3.10.0-229.24.2.el7.ppc64.rpm
kernel-debug-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
kernel-debug-devel-3.10.0-229.24.2.el7.ppc64.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
kernel-debuginfo-common-ppc64-3.10.0-229.24.2.el7.ppc64.rpm
kernel-devel-3.10.0-229.24.2.el7.ppc64.rpm
kernel-headers-3.10.0-229.24.2.el7.ppc64.rpm
kernel-tools-3.10.0-229.24.2.el7.ppc64.rpm
kernel-tools-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
kernel-tools-libs-3.10.0-229.24.2.el7.ppc64.rpm
perf-3.10.0-229.24.2.el7.ppc64.rpm
perf-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm

s390x:
kernel-3.10.0-229.24.2.el7.s390x.rpm
kernel-debug-3.10.0-229.24.2.el7.s390x.rpm
kernel-debug-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
kernel-debug-devel-3.10.0-229.24.2.el7.s390x.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
kernel-debuginfo-common-s390x-3.10.0-229.24.2.el7.s390x.rpm
kernel-devel-3.10.0-229.24.2.el7.s390x.rpm
kernel-headers-3.10.0-229.24.2.el7.s390x.rpm
kernel-kdump-3.10.0-229.24.2.el7.s390x.rpm
kernel-kdump-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
kernel-kdump-devel-3.10.0-229.24.2.el7.s390x.rpm
perf-3.10.0-229.24.2.el7.s390x.rpm
perf-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.s390x.rpm

x86_64:
kernel-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debug-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debug-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debug-devel-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.24.2.el7.x86_64.rpm
kernel-devel-3.10.0-229.24.2.el7.x86_64.rpm
kernel-headers-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-libs-3.10.0-229.24.2.el7.x86_64.rpm
perf-3.10.0-229.24.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm

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

ppc64:
kernel-debug-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
kernel-debuginfo-common-ppc64-3.10.0-229.24.2.el7.ppc64.rpm
kernel-tools-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
kernel-tools-libs-devel-3.10.0-229.24.2.el7.ppc64.rpm
perf-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm
python-perf-3.10.0-229.24.2.el7.ppc64.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.ppc64.rpm

s390x:
kernel-debug-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
kernel-debuginfo-common-s390x-3.10.0-229.24.2.el7.s390x.rpm
kernel-kdump-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
perf-debuginfo-3.10.0-229.24.2.el7.s390x.rpm
python-perf-3.10.0-229.24.2.el7.s390x.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.s390x.rpm

x86_64:
kernel-debug-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-debuginfo-common-x86_64-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
kernel-tools-libs-devel-3.10.0-229.24.2.el7.x86_64.rpm
perf-debuginfo-3.10.0-229.24.2.el7.x86_64.rpm
python-perf-3.10.0-229.24.2.el7.x86_64.rpm
python-perf-debuginfo-3.10.0-229.24.2.el7.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-2015-2925
https://access.redhat.com/security/cve/CVE-2015-5307
https://access.redhat.com/security/cve/CVE-2015-7613
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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