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

First published: Tue Sep 29 2009(Updated: )

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

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