7.2 - RHSA-2012:0670

Problem Description:

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.

2. Relevant releases/architectures:

MRG Realtime for RHEL 6 Server v.2 - noarch, x86_64

3. 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.

4. 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.

5. Bugs fixed (http://bugzilla.redhat.com/):

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