7.2 - RHSA-2012:0720

Problem Description:

Updated kernel packages that fix two security issues and multiple 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 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:

Red Hat Enterprise Linux EUS (v. 5.6 server) - i386, ia64, noarch, ppc, s390x, x86_64

3. Description:

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

This update fixes the following security issues:

* It was found that the Xen hypervisor implementation as shipped with Red Hat Enterprise Linux 5 did not properly restrict the syscall return addresses in the sysret return path to canonical addresses. An unprivileged user in a 64-bit para-virtualized guest, that is running on a 64-bit host that has an Intel CPU, could use this flaw to crash the host or, potentially, escalate their privileges, allowing them to execute arbitrary code at the hypervisor level. (CVE-2012-0217, Important)

Note: For Red Hat Enterprise Linux guests, only privileged guest users can exploit CVE-2012-0217.

* A flaw in the xfrm6_tunnel_rcv() function in the Linux kernel's IPv6 implementation could lead to a use-after-free or double free flaw in tunnel6_rcv(). A remote attacker could use this flaw to send specially-crafted packets to a target system that is using IPv6 and also has the xfrm6_tunnel kernel module loaded, causing it to crash. (CVE-2012-1583, Important)

If you do not run applications that use xfrm6_tunnel, you can prevent the xfrm6_tunnel module from being loaded by creating (as the root user) a "/etc/modprobe.d/xfrm6_tunnel.conf" file, and adding the following line to it:

blacklist xfrm6_tunnel

This way, the xfrm6_tunnel module cannot be loaded accidentally. A reboot is not necessary for this change to take effect.

Red Hat would like to thank the Xen project for reporting CVE-2012-0217. Upstream acknowledges Rafal Wojtczuk as the original reporter of CVE-2012-0217.

This update also fixes the following bugs:

* Under rare circumstances, a bug in the vsyscall interface caused the gdb debugger to terminate unexpectedly with a segmentation fault when run on the AMD64 or Intel 64 architecture. A patch has been provided to address this issue and the crashes no longer occur in the described scenario. (BZ#807929)

* Incorrect duplicate MAC addresses were being used on a rack network daughter card that contained a quad-port Intel I350 Gigabit Ethernet Controller. With this update, the underlying source code has been modified to address this issue, and correct MAC addresses are now used under all circumstances. (BZ#813195)

* When the Fibre Channel (FC) layer sets a device to "running", the layer also scans for other new devices. Previously, there was a race condition between these two operations. Consequently, for certain targets, thousands of invalid devices were created by the SCSI layer and the udev service. This update ensures that the FC layer always sets a device to "online" before scanning for others, thus fixing this bug.

Additionally, when attempting to transition priority groups on a busy FC device, the multipath layer retried immediately. If this was the only available path, a large number of retry operations were performed in a short period of time. Consequently, the logging of retry messages slowed down the system. This bug has been fixed by ensuring that the DM Multipath feature delays retry operations in the described scenario. (BZ#816683)

* Due to incorrect use of the list_for_each_entry_safe() macro, the enumeration of remote procedure calls (RPCs) priority wait queue tasks stored in the tk_wait.links list failed. As a consequence, the rpc_wake_up() and rpc_wake_up_status() functions failed to wake up all tasks. This caused the system to become unresponsive and could significantly decrease system performance. Now, the list_for_each_entry_safe() macro is no longer used in rpc_wake_up(), ensuring reasonable system performance. (BZ#817570)

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.

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/):

752304 - CVE-2012-1583 kernel: ipv6: panic using raw sockets 813428 - CVE-2012-0217 kernel: x86-64: avoid sysret to non-canonical address 817570 - Fix RPC priority queue wake up all tasks processing [rhel-5.6.z]