Synopsis

Important: kernel-rt security and bug fix update

Type/Severity

Security Advisory: Important

Topic

Updated kernel-rt packages that fix two security issues and various bugs
are now available for Red Hat Enterprise MRG 2.1.

The Red Hat Security Response Team 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.

Description

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

This update fixes the following security issues:

• When a set user ID (setuid) application is executed, certain personality

flags for controlling the application's behavior are cleared (that is, a
privileged application will not be affected by those flags). It was found
that those flags were not cleared if the application was made privileged
via file system capabilities. A local, unprivileged user could use this
flaw to change the behavior of such applications, allowing them to bypass
intended restrictions. Note that for default installations, no application
shipped by Red Hat for Red Hat Enterprise MRG is made privileged via file
system capabilities. (CVE-2012-2123, Important)

• A flaw was found in the way the Linux kernel's journal_unmap_buffer()

function handled buffer head states. On systems that have an ext4 file
system with a journal mounted, a local, unprivileged user could use this
flaw to cause a denial of service. (CVE-2011-4086, Moderate)

This update also fixes the following bugs:

• The CAP_SYS_ADMIN check was missing from the dmesg_restrict feature.

Consequently, an unprivileged and jailed root user could bypass the
dmesg_restrict protection. This update adds CAP_SYS_ADMIN to both
dmesg_restrict and kptr_restrict, which only allows writing to
dmesg_restrict when root has CAP_SYS_ADMIN. (BZ#808271)

• Previously, the _copy_from_pages() function, which is used to copy data

from the temporary buffer to the user-passed buffer, was passed the wrong
size parameter when copying data. Consequently, if the user provided a
buffer greater than PAGE_SIZE, the getxattr() syscalls were handled
incorrectly. This update fixes _copy_from_pages() to use the ACL length,
which uses a correctly-sized buffer. (BZ#753230)

• Some older versions of hardware or their software could not recognize

certain commands and would log messages for illegal or unsupported errors
the driver could not properly handle. This bug has been fixed and no bogus
error messages are now returned in the described scenario. (BZ#813892)

• Previously, the qla2x00_poll() function did the local_irq_save() call

before calling qla24xx_intr_handler(), which had a spinlock. Since
spinlocks are sleepable in the real-time kernel, it is not allowed to call
them with interrupts disabled. This scenario produced error messages and
could cause a system deadlock. With this update, the
local_irq_save_nort(flags) function is used to save flags without disabling
interrupts, which prevents potential deadlocks and removes the error
messages. (BZ#818220)

Users should upgrade to these updated packages, which 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.

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
https://access.redhat.com/knowledge/articles/11258

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.

Affected Products

• MRG Realtime 2 x86_64

Fixes

• BZ - 749143 - CVE-2011-4086 kernel: jbd2: unmapped buffer with _Unwritten or _Delay flags set can lead to DoS
• BZ - 806722 - CVE-2012-2123 kernel: fcaps: clear the same personality flags as suid when fcaps are used
• BZ - 818220 - qla2xxx does a spinlock with interrupts disabled

CVEs

• CVE-2011-4086
• CVE-2012-2123

References