RHEL 6 : kernel (RHSA-2015:1623)

This script is Copyright (C) 2015-2017 Tenable Network Security, Inc.


Synopsis :

The remote Red Hat host is missing one or more security updates.

Description :

Updated kernel packages that fix two security issues and several bugs
are now available for Red Hat Enterprise Linux 6.

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.

[Updated 3 September 2015] This advisory has been updated to push
packages into the Red Hat Enterprise Linux 6 Client channels. The
packages included in this revised update have not been changed in any
way from the packages included in the original advisory.

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

Two flaws were found in the way the Linux kernel's networking
implementation handled UDP packets with incorrect checksum values. A
remote attacker could potentially use these flaws to trigger an
infinite loop in the kernel, resulting in a denial of service on the
system, or cause a denial of service in applications using the edge
triggered epoll functionality. (CVE-2015-5364, CVE-2015-5366,
Important)

This update also fixes the following bugs :

* When removing a directory, and a reference was held to that
directory by a reference to a negative child dentry, the directory
dentry was previously not killed. In addition, once the negative child
dentry was killed, an unlinked and unused dentry was present in the
cache. As a consequence, deadlock could be caused by forcing the
dentry eviction while the file system in question was frozen. With
this update, all unused dentries are unhashed and evicted just after a
successful directory removal, which avoids the deadlock, and the
system no longer hangs in the aforementioned scenario. (BZ#1243400)

* Due to the broken s_umount lock ordering, a race condition occurred
when an unlinked file was closed and the sync (or syncfs) utility was
run at the same time. As a consequence, deadlock occurred on a frozen
file system between sync and a process trying to unfreeze the file
system. With this update, sync (or syncfs) is skipped on a frozen file
system, and deadlock no longer occurs in the aforementioned situation.
(BZ#1243404)

* Previously, in the scenario when a file was opened by file handle
(fhandle) with its dentry not present in dcache ('cold dcache') and
then making use of the unlink() and close() functions, the inode was
not freed upon the close() system call. As a consequence, the iput()
final was delayed indefinitely. A patch has been provided to fix this
bug, and the inode is now freed as expected. (BZ#1243406)

* Due to a corrupted Executable and Linkable Format (ELF) header in
the /proc/vmcore file, the kdump utility failed to provide any
information. The underlying source code has been patched, and kdump
now provides debuging information for kernel crashes as intended.
(BZ#1245195)

* Previously, running the multipath request queue caused regressions
in cases where paths failed regularly under I/O load. This regression
manifested as I/O stalls that exceeded 300 seconds. This update
reverts the changes aimed to reduce running the multipath request
queue resulting in I/O completing in a timely manner. (BZ#1246095)

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.

See also :

https://www.redhat.com/security/data/cve/CVE-2015-5364.html
https://www.redhat.com/security/data/cve/CVE-2015-5366.html
http://rhn.redhat.com/errata/RHSA-2015-1623.html

Solution :

Update the affected packages.

Risk factor :

High / CVSS Base Score : 7.8
(CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:C)
CVSS Temporal Score : 5.8
(CVSS2#E:U/RL:OF/RC:C)
Public Exploit Available : false

Family: Red Hat Local Security Checks

Nessus Plugin ID: 85396 ()

Bugtraq ID:

CVE ID: CVE-2015-5364
CVE-2015-5366

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