Red Hat Enterprise Linux 5.3 RHSA-2009:1466-01 Important Security Update

The kernel packages contain the Linux kernel, the core of any Linux operating system.
This update includes backported fixes for two security issues. These issues only affected users of Red Hat Enterprise Linux 5.3 Extended Update Support as they have already been addressed for users of Red Hat Enterprise Linux 5 in the 5.4 update, RHSA-2009:1243.
In accordance with the support policy, future security updates to Red Hat Enterprise Linux 5.3 Extended Update Support will only include issues of critical security impact.
This update fixes the following security issues:
* it was discovered that, when executing a new process, the clear_child_tid pointer in the Linux kernel is not cleared. If this pointer points to a writable portion of the memory of the new program, the kernel could corrupt four bytes of memory, possibly leading to a local denial of service or privilege escalation. (CVE-2009-2848, Important)
* a flaw was found in the way the do_sigaltstack() function in the Linux kernel copies the stack_t structure to user-space. On 64-bit machines, this flaw 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 Multipath environments, this could cause paths to fail, or possibly prevent successful 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 checks after the first use of a pointer. NULL pointer bugs are often exploited by attackers, 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 calibration could have also caused the system time to become faster or slower. With this update, it is still possible for APIC timer calibration issues to occur; 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/LFENCE is used instead of CPUID for gettimeofday() serialization, which resolves this issue. (BZ#523280)
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.