The kernel packages contain the Linux kernel, the core of any Linux operating system.
This update fixes the following security issues:
A NULL pointer dereference flaw was found in the Linux kernel's Stream Control Transmission Protocol (SCTP) implementation. A remote attacker could send a specially-crafted SCTP packet to a target system, resulting in a denial of service. (CVE-2011-2482, Important)
A flaw in the Linux kernel's client-side NFS Lock Manager (NLM) implementation could allow a local, unprivileged user to cause a denial of service. (CVE-2011-2491, Important)
Buffer overflow flaws in the Linux kernel's netlink-based wireless configuration interface implementation could allow a local user, who has the CAP_NET_ADMIN capability, to cause a denial of service or escalate their privileges on systems that have an active wireless interface. (CVE-2011-2517, Important)
A flaw was found in the way the Linux kernel's Xen hypervisor implementation emulated the SAHF instruction. When using a fully-virtualized guest on a host that does not use hardware assisted paging (HAP), such as those running CPUs that do not have support for (or those that have it disabled) Intel Extended Page Tables (EPT) or AMD Virtualization (AMD-V) Rapid Virtualization Indexing (RVI), a privileged guest user could trigger this flaw to cause the hypervisor to crash. (CVE-2011-2519, Moderate)
An off-by-one flaw was found in the __addr_ok() macro in the Linux kernel's Xen hypervisor implementation when running on 64-bit systems. A privileged guest user could trigger this flaw to cause the hypervisor to crash. (CVE-2011-2901, Moderate)
/proc/[PID]/io is world-readable by default. Previously, these files could be read without any further restrictions. A local, unprivileged user could read these files, belonging to other, possibly privileged processes to gather confidential information, such as the length of a password used in a process. (CVE-2011-2495, Low)
Red Hat would like to thank Vasily Averin for reporting CVE-2011-2491, and Vasiliy Kulikov of Openwall for reporting CVE-2011-2495.
This update also fixes several bugs. Documentation for these bug fixes will be available shortly from the Technical Notes document linked to in the References section.
Users should upgrade to these updated packages, which contain backported patches to correct these issues, and fix the bugs noted in the Technical Notes. The system must be rebooted for this update to take effect.