RHSA-2015:0726: Important: kernel security and bug fix update

The kernel packages contain the Linux kernel, the core of any Linuxoperating system. It was found that the Linux kernel's Infiniband subsystem did not properly sanitize input parameters while registering memory regions fromuser space via the (u)verbs API. A local user with access to a/dev/infiniband/uverbsX device could use this flaw to crash the system or,potentially, escalate their privileges on the system. (CVE-2014-8159,Important) A use-after-free flaw was found in the way the Linux kernel's SCTP implementation handled authentication key reference counting during INITcollisions. A remote attacker could use this flaw to crash the system or,potentially, escalate their privileges on the system. (CVE-2015-1421,Important)Red Hat would like to thank Mellanox for reporting the CVE-2014-8159 issue.The CVE-2015-1421 issue was discovered by Sun Baoliang of Red Hat.This update also fixes the following bugs: In certain systems with multiple CPUs, when a crash was triggered on one CPU with an interrupt handler and this CPU sent Non-Maskable Interrupt(NMI) to another CPU, and, at the same time, ioapiclock had already beenacquired, a deadlock occurred in ioapiclock. As a consequence, the kdumpservice could become unresponsive. This bug has been fixed and kdump nowworks as expected. (BZ#1197742) On Lenovo X1 Carbon 3rd Gen, X250, and T550 laptops, the thinkpadacpi module was not properly loaded, and thus the function keys and radioswitches did not work. This update applies a new string pattern of BIOSversion, which fixes this bug, and function keys and radio switches nowwork as intended. (BZ#1197743) During a heavy file system load involving many worker threads, all worker threads in the pool became blocked on a resource, and no manager threadexisted to create more workers. As a consequence, the running processesbecame unresponsive. With this update, the logic around manager creationhas been changed to assure that the last worker thread becomes a managerthread and does not start executing work items. Now, a manager threadexists, spawns new workers as needed, and processes no longer hang.(BZ#1197744) If a thin-pool's metadata enters read-only or fail mode, for example, due to thin-pool running out of metadata or data space, any attempt to makemetadata changes such as creating a thin device or snapshot thin deviceshould error out cleanly. However, previously, the kernel code returnedverbose and alarming error messages to the user. With this update, due toearly trapping of attempt to make metadata changes, informative errors aredisplayed, no longer unnecessarily alarming the user. (BZ#1197745) When running Red Hat Enterprise Linux as a guest on Microsoft Hyper-V hypervisor, the storvsc module did not return the correct error code forthe upper level Small Computer System Interface (SCSI) subsystem. As aconsequence, a SCSI command failed and storvsc did not handle such afailure properly under some conditions, for example, when RAID devices werecreated on top of storvsc devices. An upstream patch has been applied tofix this bug, and storvsc now returns the correct error code in thedescribed situation. (BZ#1197749)All kernel users are advised to upgrade to these updated packages, whichcontain backported patches to correct these issues. The system must berebooted for this update to take effect.