RHSA-2009:1239: Important: kernel-rt security and bug fix update

The kernel-rt packages contain the Linux kernel, the core of any Linuxoperating system.These updated packages fix the following security issues: Tavis Ormandy and Julien Tinnes of the Google Security Team reported a flaw in the SOCKOPSWRAP macro in the Linux kernel. This macro did notinitialize the sendpage operation in the protoops structure correctly. Alocal, unprivileged user could use this flaw to cause a local denial ofservice or escalate their privileges. (CVE-2009-2692, Important) 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: 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#511187) a bug in the locking strategy for the freepagesbulk() kernel function was found, where a lock in a code branch was not held. This could havecreated a "double free" problem that resulted in a kernel panic.(BZ#513715) udevd and multipathd were unable to service events fast enough when a Fibre Channel cable was unplugged. This caused the cable state to be out ofsync if the cable was plugged back in quickly, possibly resulting indevices being removed, or path issues when using Device-Mapper Multipath.This has been changed so that users can specify devices that should not beremoved if a cable is unplugged. (BZ#514541) a race condition in exitthread() could have eventually caused a kernel oops. (BZ#514587) a race condition was fixed between kthreadstop() and kthreadcreate(). Kernel subsystems creating and stopping threads at a fast pace could hitthis issue. Several inexplicable backtraces observed during testscaused this race condition. (BZ#518967) HPETEMULATERTC was being disabled during kernel compile. This was caused by an incorrect requirement in the related Kconfig entry. This issueled to failures when accessing the RTC (real time clock) in machines thathad the RTC emulated by HPET (High Precision Event Timer). (BZ#519433)Users should upgrade to these updated packages, which contain backportedpatches to correct these issues. The system must be rebooted for thisupdate to take effect.