【CESA-2016:2124 】An update for kernel is now available for Red Hat Enterprise Linux 5

CESA-2016:2124

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.

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)

Bugs Fixed

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