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AUSCERT External Security Bulletin Redistribution
Important: kernel security and bug fix update
24 October 2012
AusCERT Security Bulletin Summary
Publisher: Red Hat
Operating System: Red Hat Enterprise Linux Server 6
Impact/Access: Denial of Service -- Remote/Unauthenticated
CVE Names: CVE-2012-3412
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Red Hat Security Advisory
Synopsis: Important: kernel security and bug fix update
Advisory ID: RHSA-2012:1401-01
Product: Red Hat Enterprise Linux
Advisory URL: https://rhn.redhat.com/errata/RHSA-2012-1401.html
Issue date: 2012-10-23
CVE Names: CVE-2012-3412
Updated kernel packages that fix one security issue and several bugs are
now available for Red Hat Enterprise Linux 6.2 Extended Update Support.
The Red Hat Security Response Team has rated this update as having
important security impact. A Common Vulnerability Scoring System (CVSS)
base score, which gives a detailed severity rating, is available from the
CVE link in the References section.
2. Relevant releases/architectures:
Red Hat Enterprise Linux Server EUS (v. 6.2) - i386, noarch, ppc64, s390x, x86_64
Red Hat Enterprise Linux Server Optional EUS (v. 6.2) - i386, ppc64, s390x, x86_64
The kernel packages contain the Linux kernel, the core of any Linux
This update fixes the following security issue:
* A flaw was found in the way socket buffers (skb) requiring TSO (TCP
segment offloading) were handled by the sfc driver. If the skb did not fit
within the minimum-size of the transmission queue, the network card could
repeatedly reset itself. A remote attacker could use this flaw to cause a
denial of service. (CVE-2012-3412, Important)
Red Hat would like to thank Ben Hutchings of Solarflare (tm) for reporting
This update also fixes the following bugs:
* Previously, when a server attempted to shut down a socket, the
svc_tcp_sendto() function set the XPT_CLOSE variable if the entire reply
failed to be transmitted. However, before XPT_CLOSE could be acted upon,
other threads could send further replies before the socket was really shut
down. Consequently, data corruption could occur in the RPC record marker.
With this update, send operations on a closed socket are stopped
immediately, thus preventing this bug. (BZ#853256)
* When a PIT (Programmable Interval Timer) MSB (Most Significant Byte)
transition occurred very close to an SMI (System Management Interrupt)
execution, the pit_verify_msb() function did not see the MSB transition.
Consequently, the pit_expect_msb() function returned success incorrectly,
eventually causing a large clock drift in the quick_pit_calibrate()
function. As a result, the TSC (Time Stamp Counter) calibration on some
systems was off by Ã‚Â± 20 MHz, which led to inaccurate timekeeping or ntp
synchronization failures. This update fixes pit_expect_msb() and the clock
drift no longer occurs in the described scenario. (BZ#853952)
* Sometimes, the crypto allocation code could become unresponsive for 60
seconds or multiples thereof due to an incorrect notification mechanism.
This could cause applications, like Openswan, to become unresponsive. The
notification mechanism has been improved to avoid such hangs. (BZ#854475)
* Traffic to the NFS server could trigger a kernel oops in the
svc_tcp_clear_pages() function. The source code has been modified, and the
kernel oops no longer occurs in this scenario. (BZ#856105)
* Under certain circumstances, a system crash could result in data loss on
XFS file systems. If files were created immediately before the file system
was left to idle for a long period of time and then the system crashed,
those files could appear as zero-length once the file system was remounted.
This occurred even if a sync or fsync was run on the files. This was
because XFS was not correctly idling the journal, and therefore it
incorrectly replayed the inode allocation transactions upon mounting after
the system crash, which zeroed the file size. This problem has been fixed
by re-instating the periodic journal idling logic to ensure that all
metadata is flushed within 30 seconds of modification, and the journal is
updated to prevent incorrect recovery operations from occurring.
* On architectures with the 64-bit cputime_t type, it was possible to
trigger the "divide by zero" error, namely, on long-lived processes. A
patch has been applied to address this problem, and the "divide by zero"
error no longer occurs under these circumstances. (BZ#856702)
Users should upgrade to these updated packages, which contain backported
patches to resolve these issues. The system must be rebooted for this
update to take effect.
Before applying this update, make sure all previously-released errata
relevant to your system have been applied.
This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
To install kernel packages manually, use "rpm -ivh [package]". Do not
use "rpm -Uvh" as that will remove the running kernel binaries from
your system. You may use "rpm -e" to remove old kernels after
determining that the new kernel functions properly on your system.
5. Bugs fixed (http://bugzilla.redhat.com/):
844714 - CVE-2012-3412 kernel: sfc: potential remote denial of service through TCP MSS option
6. Package List:
Red Hat Enterprise Linux Server EUS (v. 6.2):
Red Hat Enterprise Linux Server Optional EUS (v. 6.2):
These packages are GPG signed by Red Hat for security. Our key and
details on how to verify the signature are available from
The Red Hat security contact is <email@example.com>. More contact
details at https://access.redhat.com/security/team/contact/
Copyright 2012 Red Hat, Inc.
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