RHSA-2009:1466: Important: kernel security and bug fix update

The kernel packages contain the Linux kernel, the core of any Linuxoperating system.This update includes backported fixes for two security issues. These issuesonly affected users of Red Hat Enterprise Linux 5.3 Extended Update Supportas they have already been addressed for users of Red Hat Enterprise Linux 5in the 5.4 update, RHSA-2009:1243.In accordance with the support policy, future security updates to Red HatEnterprise Linux 5.3 Extended Update Support will only include issues ofcritical security impact.This update fixes the following security issues: it was discovered that, when executing a new process, the clearchildtid pointer in the Linux kernel is not cleared. If this pointer points to awritable portion of the memory of the new program, the kernel could corruptfour bytes of memory, possibly leading to a local denial of service orprivilege escalation. (CVE-2009-2848, Important) a flaw was found in the way the dosigaltstack() function in the Linux kernel copies the stackt structure to user-space. On 64-bit machines, thisflaw could lead to a four-byte information leak. (CVE-2009-2847, Moderate)This update also fixes the following bugs: a regression was found in the SCSI retry logic: SCSI mode select was not retried when retryable errors were encountered. In Device-Mapper Multipathenvironments, this could cause paths to fail, or possibly preventsuccessful failover. (BZ#506905) the gcc flag "-fno-delete-null-pointer-checks" was added to the kernel build options. This prevents gcc from optimizing out NULL pointer checksafter the first use of a pointer. NULL pointer bugs are often exploited byattackers, and keeping these checks is considered a safety measure.(BZ#515468) due to incorrect APIC timer calibration, a system hang could have occurred while booting certain systems. This incorrect timer calibrationcould have also caused the system time to become faster or slower. Withthis update, it is still possible for APIC timer calibration issues tooccur; however, a clear warning is now provided if they do. (BZ#521237) gettimeofday() experienced poor performance (which caused performance problems for applications using gettimeofday()) when running on hypervisorsthat use hardware assisted virtualization. With this update, MFENCE/LFENCEis used instead of CPUID for gettimeofday() serialization, which resolvesthis issue. (BZ#523280)Users should upgrade to these updated packages, which contain backportedpatches to correct these issues. The system must be rebooted for thisupdate to take effect.