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Category:   OS (Linux)  >   Linux Kernel Vendors:   kernel.org
(Red Hat Issues Fix) Linux Kernel Copy-on-Write Memory Management Race Condition Lets Local Users Obtain Elevated Privileges
SecurityTracker Alert ID:  1037147
SecurityTracker URL:  http://securitytracker.com/id/1037147
CVE Reference:   CVE-2016-5195   (Links to External Site)
Date:  Oct 28 2016
Impact:   Execution of arbitrary code via local system, Root access via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): RHEL 5
Description:   A vulnerability was reported in the Linux kernel. A local user can obtain root privileges on the target system.

A local user can a race condition in the kernel memory subsystem in the management of copy-on-write operations on read-only memory mappings to overwrite kernel memory and gain kernel-level privileges.

This vulnerability is being actively exploited.

Some demonstration exploit code is listed at:

https://github.com/dirtycow/dirtycow.github.io/wiki/PoCs

Impact:   A local user can obtain root privileges on the target system.
Solution:   Red Hat has issued a fix.

The Red Hat advisory is available at:

https://rhn.redhat.com/errata/RHSA-2016-2124.html

Vendor URL:  rhn.redhat.com/errata/RHSA-2016-2124.html (Links to External Site)
Cause:   Access control error, State error

Message History:   This archive entry is a follow-up to the message listed below.
Oct 22 2016 Linux Kernel Copy-on-Write Memory Management Race Condition Lets Local Users Obtain Elevated Privileges



 Source Message Contents

Subject:  [RHSA-2016:2124-01] Important: kernel security and bug fix update

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

Synopsis:          Important: kernel security and bug fix update
Advisory ID:       RHSA-2016:2124-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://rhn.redhat.com/errata/RHSA-2016-2124.html
Issue date:        2016-10-28
CVE Names:         CVE-2016-1583 CVE-2016-5195 
=====================================================================

1. Summary:

An update for kernel is now available for Red Hat Enterprise Linux 5.

Red Hat Product Security has rated this update as having a security impact
of Important. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available for each vulnerability
from the CVE link(s) in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux (v. 5 server) - i386, ia64, noarch, ppc, s390x, x86_64
Red Hat Enterprise Linux Desktop (v. 5 client) - i386, noarch, x86_64

3. Description:

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

Security Fix(es):

* A race condition was found in the way the Linux kernel's memory subsystem
handled the copy-on-write (COW) breakage of private read-only memory
mappings. An unprivileged, local user could use this flaw to gain write
access to otherwise read-only memory mappings and thus increase their
privileges on the system. (CVE-2016-5195, Important)

* It was found that stacking a file system over procfs in the Linux kernel
could lead to a kernel stack overflow due to deep nesting, as demonstrated
by mounting ecryptfs over procfs and creating a recursion by mapping
/proc/environ. An unprivileged, local user could potentially use this flaw
to escalate their privileges on the system. (CVE-2016-1583, Important)

Red Hat would like to thank Phil Oester for reporting CVE-2016-5195.

Bug Fix(es):

* In some cases, a kernel crash or file system corruption occurred when
running journal mode 'ordered'. The kernel crash was caused by a null
pointer dereference due to a race condition between two journal functions.
The file system corruption occurred due to a race condition between the
do_get_write_access() function and buffer writeout. This update fixes both
race conditions. As a result, neither the kernel crash, nor the file system
corruption now occur. (BZ#1067708)

* Prior to this update, some Global File System 2 (GFS2) files had
incorrect time stamp values due to two problems with handling time stamps
of such files. The first problem concerned the atime time stamp, which
ended up with an arbitrary value ahead of the actual value, when a GFS2
file was accessed. The second problem was related to the mtime and ctime
time stamp updates, which got lost when a GFS2 file was written to from one
node and read from or written to from another node. With this update, a set
of patches has been applied that fix these problems. As a result, the time
stamps of GFS2 files are now handled correctly. (BZ#1374861)

4. Solution:

For details on how to apply this update, which includes the changes
described in this advisory, refer to:

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

The system must be rebooted for this update to take effect.

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

1344721 - CVE-2016-1583 kernel: Stack overflow via ecryptfs and /proc/$pid/environ
1384344 - CVE-2016-5195 kernel: mm: privilege escalation via MAP_PRIVATE COW breakage

6. Package List:

Red Hat Enterprise Linux Desktop (v. 5 client):

Source:
kernel-2.6.18-416.el5.src.rpm

i386:
kernel-2.6.18-416.el5.i686.rpm
kernel-PAE-2.6.18-416.el5.i686.rpm
kernel-PAE-debuginfo-2.6.18-416.el5.i686.rpm
kernel-PAE-devel-2.6.18-416.el5.i686.rpm
kernel-debug-2.6.18-416.el5.i686.rpm
kernel-debug-debuginfo-2.6.18-416.el5.i686.rpm
kernel-debug-devel-2.6.18-416.el5.i686.rpm
kernel-debuginfo-2.6.18-416.el5.i686.rpm
kernel-debuginfo-common-2.6.18-416.el5.i686.rpm
kernel-devel-2.6.18-416.el5.i686.rpm
kernel-headers-2.6.18-416.el5.i386.rpm
kernel-xen-2.6.18-416.el5.i686.rpm
kernel-xen-debuginfo-2.6.18-416.el5.i686.rpm
kernel-xen-devel-2.6.18-416.el5.i686.rpm

noarch:
kernel-doc-2.6.18-416.el5.noarch.rpm

x86_64:
kernel-2.6.18-416.el5.x86_64.rpm
kernel-debug-2.6.18-416.el5.x86_64.rpm
kernel-debug-debuginfo-2.6.18-416.el5.x86_64.rpm
kernel-debug-devel-2.6.18-416.el5.x86_64.rpm
kernel-debuginfo-2.6.18-416.el5.x86_64.rpm
kernel-debuginfo-common-2.6.18-416.el5.x86_64.rpm
kernel-devel-2.6.18-416.el5.x86_64.rpm
kernel-headers-2.6.18-416.el5.x86_64.rpm
kernel-xen-2.6.18-416.el5.x86_64.rpm
kernel-xen-debuginfo-2.6.18-416.el5.x86_64.rpm
kernel-xen-devel-2.6.18-416.el5.x86_64.rpm

Red Hat Enterprise Linux (v. 5 server):

Source:
kernel-2.6.18-416.el5.src.rpm

i386:
kernel-2.6.18-416.el5.i686.rpm
kernel-PAE-2.6.18-416.el5.i686.rpm
kernel-PAE-debuginfo-2.6.18-416.el5.i686.rpm
kernel-PAE-devel-2.6.18-416.el5.i686.rpm
kernel-debug-2.6.18-416.el5.i686.rpm
kernel-debug-debuginfo-2.6.18-416.el5.i686.rpm
kernel-debug-devel-2.6.18-416.el5.i686.rpm
kernel-debuginfo-2.6.18-416.el5.i686.rpm
kernel-debuginfo-common-2.6.18-416.el5.i686.rpm
kernel-devel-2.6.18-416.el5.i686.rpm
kernel-headers-2.6.18-416.el5.i386.rpm
kernel-xen-2.6.18-416.el5.i686.rpm
kernel-xen-debuginfo-2.6.18-416.el5.i686.rpm
kernel-xen-devel-2.6.18-416.el5.i686.rpm

ia64:
kernel-2.6.18-416.el5.ia64.rpm
kernel-debug-2.6.18-416.el5.ia64.rpm
kernel-debug-debuginfo-2.6.18-416.el5.ia64.rpm
kernel-debug-devel-2.6.18-416.el5.ia64.rpm
kernel-debuginfo-2.6.18-416.el5.ia64.rpm
kernel-debuginfo-common-2.6.18-416.el5.ia64.rpm
kernel-devel-2.6.18-416.el5.ia64.rpm
kernel-headers-2.6.18-416.el5.ia64.rpm
kernel-xen-2.6.18-416.el5.ia64.rpm
kernel-xen-debuginfo-2.6.18-416.el5.ia64.rpm
kernel-xen-devel-2.6.18-416.el5.ia64.rpm

noarch:
kernel-doc-2.6.18-416.el5.noarch.rpm

ppc:
kernel-2.6.18-416.el5.ppc64.rpm
kernel-debug-2.6.18-416.el5.ppc64.rpm
kernel-debug-debuginfo-2.6.18-416.el5.ppc64.rpm
kernel-debug-devel-2.6.18-416.el5.ppc64.rpm
kernel-debuginfo-2.6.18-416.el5.ppc64.rpm
kernel-debuginfo-common-2.6.18-416.el5.ppc64.rpm
kernel-devel-2.6.18-416.el5.ppc64.rpm
kernel-headers-2.6.18-416.el5.ppc.rpm
kernel-headers-2.6.18-416.el5.ppc64.rpm
kernel-kdump-2.6.18-416.el5.ppc64.rpm
kernel-kdump-debuginfo-2.6.18-416.el5.ppc64.rpm
kernel-kdump-devel-2.6.18-416.el5.ppc64.rpm

s390x:
kernel-2.6.18-416.el5.s390x.rpm
kernel-debug-2.6.18-416.el5.s390x.rpm
kernel-debug-debuginfo-2.6.18-416.el5.s390x.rpm
kernel-debug-devel-2.6.18-416.el5.s390x.rpm
kernel-debuginfo-2.6.18-416.el5.s390x.rpm
kernel-debuginfo-common-2.6.18-416.el5.s390x.rpm
kernel-devel-2.6.18-416.el5.s390x.rpm
kernel-headers-2.6.18-416.el5.s390x.rpm
kernel-kdump-2.6.18-416.el5.s390x.rpm
kernel-kdump-debuginfo-2.6.18-416.el5.s390x.rpm
kernel-kdump-devel-2.6.18-416.el5.s390x.rpm

x86_64:
kernel-2.6.18-416.el5.x86_64.rpm
kernel-debug-2.6.18-416.el5.x86_64.rpm
kernel-debug-debuginfo-2.6.18-416.el5.x86_64.rpm
kernel-debug-devel-2.6.18-416.el5.x86_64.rpm
kernel-debuginfo-2.6.18-416.el5.x86_64.rpm
kernel-debuginfo-common-2.6.18-416.el5.x86_64.rpm
kernel-devel-2.6.18-416.el5.x86_64.rpm
kernel-headers-2.6.18-416.el5.x86_64.rpm
kernel-xen-2.6.18-416.el5.x86_64.rpm
kernel-xen-debuginfo-2.6.18-416.el5.x86_64.rpm
kernel-xen-devel-2.6.18-416.el5.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-2016-1583
https://access.redhat.com/security/cve/CVE-2016-5195
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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