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Red Hat Security Advisory
Synopsis: Moderate: kernel security and bug fix update
Advisory ID: RHSA-2011:1321-01
Product: Red Hat Enterprise Linux
Advisory URL: https://rhn.redhat.com/errata/RHSA-2011-1321.html
Issue date: 2011-09-20
CVE Names: CVE-2011-2723
Updated kernel packages that fix one security issue and several bugs are
now available for Red Hat Enterprise Linux 5.6 Extended Update Support.
The Red Hat Security Response Team has rated this update as having moderate
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 (v. 5 server) - i386, ia64, noarch, ppc, s390x, x86_64
The kernel packages contain the Linux kernel.
* A flaw in skb_gro_header_slow() in the Linux kernel could lead to GRO
(Generic Receive Offload) fields being left in an inconsistent state. An
attacker on the local network could use this flaw to trigger a denial of
service. (CVE-2011-2723, Moderate)
Red Hat would like to thank Brent Meshier for reporting this issue.
* When reading a file from a subdirectory in /proc/bus/pci/ while
hot-unplugging the device related to that file, the system will crash. Now,
the kernel correctly handles the simultaneous removal of a device and
access to the representation of that device in the proc file system.
* RHSA-2011:0017 introduced a regression: Non-disk SCSI devices (except for
tape drives) such as enclosure or CD-ROM devices were hidden when attached
to a SAS based RAID controller that uses the megaraid_sas driver. With this
update, such devices are accessible, as expected. (BZ#726487)
* The fix for CVE-2010-3432 provided in RHSA-2011:0004 introduced a
regression: Information in sctp_packet_config(), which was called before
appending data chunks to a packet, was not reset, causing considerably poor
SCTP (Stream Control Transmission Protocol) performance. With this update,
the packet information is reset after transmission. (BZ#727591)
* Certain systems do not correctly set the ACPI FADT APIC mode bit. They
set the bit to "cluster" mode instead of "physical" mode which caused these
systems to boot without the TSC (Time Stamp Counter). With this update, the
ACPI FADT check has been removed due to its unreliability. (BZ#728162)
* Performance when invalidating and rereading cached data as a glock moves
around the cluster with GFS2 is improved. (BZ#729082)
* Performance issues occurred when multiple nodes attempted to call mmap()
on the same inode at the same time on a GFS2 file system, as it was using
an exclusive glock. With this update, a shared lock is used when "noatime"
is set on the mount, allowing mmap() operations to occur in parallel,
fixing this bug. Note that this issue only refers to mmap() system calls,
and not to subsequent page faults. (BZ#729090)
* Some of the functions in the GFS2 file system were not reserving enough
space for the resource group header in a transaction and for resource
groups bit blocks that get added when a memory allocation is performed.
That resulted in failed write and allocation operations. With this update,
GFS2 makes sure to reserve space in the described scenario, using the new
gfs2_rg_blocks() inline function. (BZ#729092)
* When GFS2 grew the file system, it never reread the rindex file during
the grow. This is necessary for large grows when the file system is almost
full, and GFS2 needs to use some of the space allocated earlier in the grow
to complete it. Now, if GFS2 fails to reserve the necessary space and the
rindex data is not up-to-date, it rereads it. (BZ#729094)
* Previously, when the Xen hypervisor split a 2 MB page into 4 KB pages, it
linked the new page from PDE (Page Directory Entry) before it filled
entries of the page with appropriate data. Consequently, when doing a live
migration with EPT (Extended Page Tables) enabled on a non-idle guest
running with more than two virtual CPUs, the guest often terminated
unexpectedly. With this update, the Xen hypervisor prepares the page table
entry first, and then links it in. (BZ#730684)
* Changes made to TSC as a clock source for IRQs caused virtual machines
running under the VMware ESX or ESXi hypervisors to become unresponsive
during the initial kernel boot process. With this update, the
enable_tsc_timer flag enables the do_timer_tsc_timekeeping() function to be
called in the do_timer_interrupt_hook() function, preventing a deadlock in
the timer interrupt handler. (BZ#730688)
Users should upgrade to these updated packages, which contain backported
patches to correct 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/):
726552 - CVE-2011-2723 kernel: gro: only reset frag0 when skb can be pulled
729090 - mmapping a read only file on a gfs2 filesystem incorrectly acquires an exclusive glock
729092 - GFS2: Not enough space reserved in gfs2_write_begin and possibly elsewhere.
729094 - GFS2: Kernel changes necessary to allow growing completely full filesystems.
6. Package List:
Red Hat Enterprise Linux (v. 5 server):
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 2011 Red Hat, Inc.
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