RHSA-2015:1623 - Security Advisory

Topic

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.

Description

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.

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

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.7 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 6.7 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 6.7 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux for SAP Solutions for x86_64 - Extended Update Support 6.7 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.7 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.7 i386
• Red Hat Enterprise Linux EUS Compute Node 6.7 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

• BZ - 1239029 - CVE-2015-5366 CVE-2015-5364 kernel: net: incorrect processing of checksums in UDP implementation

CVEs

• CVE-2015-5364
• CVE-2015-5366

References

• http://www.redhat.com/security/updates/classification/#normal