The kernel packages contain the Linux kernel, the core of any Linux operating system.
This update fixes the following security issues:
The way IPv4 and IPv6 protocol sequence numbers and fragment IDs were generated could allow a man-in-the-middle attacker to inject packets and possibly hijack connections. Protocol sequence numbers and fragment IDs are now more random. (CVE-2011-3188, Moderate)
A flaw was found in the Linux kernel's clock implementation on 32-bit, SMP (symmetric multiprocessing) systems. A local, unprivileged user could use this flaw to cause a divide error fault, resulting in a denial of service. (CVE-2011-3209, Moderate)
Red Hat would like to thank Dan Kaminsky for reporting CVE-2011-3188, and Yasuaki Ishimatsu for reporting CVE-2011-3209.
In addition, this update fixes the following bugs:
When the Global File System 2 (GFS2) file system is suspended, its delete work queue is also suspended, along with any pending work on the queue. Prior to this update, if GFS2's transaction lock was demoted while the delete work queue was suspended, a deadlock could occur on the file system because the file system tried to flush the work queue in the lock demotion code. With this update, the delete work queue is no longer flushed by the lock demotion code, and a deadlock no longer occurs. Instead, the work queue is flushed by the unmount operation, so that pending work is properly completed. (BZ#733678)
A previously applied patch introduced a regression for third-party file systems that do not set the FS_HAS_IODONE2 flag, specifically, Oracle Cluster File System 2 (OCFS2). The patch removed a call to the aio_complete function, resulting in no completion events being processed, causing user-space applications to become unresponsive. This update reintroduces the aio_complete function call, fixing this issue. (BZ#734156)
Certain devices support multiple operation modes. For example, EMC CLARiiON disk arrays support ALUA mode and their own vendor specific mode for failover. In Red Hat Enterprise Linux 5.5, a bug was discovered that prevented tools such as multipath from being able to select the device/hardware handler plug-in to use. This resulted in the application (for example, multipath) not working properly. With this update, the kernel has been modified to allow applications to select the device/hardware handler to use, thus resolving this issue. (BZ#739900)
This update improves the performance of delete/unlink operations in a GFS2 file system with large files by adding a layer of metadata read-ahead for indirect blocks. (BZ#743805)
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.