Red Hat Enterprise Linux 7 RHSA-2015:0726-01 Kernel Important Fixes

The kernel packages contain the Linux kernel, the core of any Linux operating system.
* It was found that the Linux kernel's Infiniband subsystem did not properly sanitize input parameters while registering memory regions from user 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 INIT collisions. 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, ioapic_lock had already been acquired, a deadlock occurred in ioapic_lock. As a consequence, the kdump service could become unresponsive. This bug has been fixed and kdump now works as expected. (BZ#1197742)
* On Lenovo X1 Carbon 3rd Gen, X250, and T550 laptops, the thinkpad_acpi module was not properly loaded, and thus the function keys and radio switches did not work. This update applies a new string pattern of BIOS version, which fixes this bug, and function keys and radio switches now work 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 thread existed to create more workers. As a consequence, the running processes became unresponsive. With this update, the logic around manager creation has been changed to assure that the last worker thread becomes a manager thread and does not start executing work items. Now, a manager thread exists, 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 make metadata changes such as creating a thin device or snapshot thin device should error out cleanly. However, previously, the kernel code returned verbose and alarming error messages to the user. With this update, due to early trapping of attempt to make metadata changes, informative errors are displayed, 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 for the upper level Small Computer System Interface (SCSI) subsystem. As a consequence, a SCSI command failed and storvsc did not handle such a failure properly under some conditions, for example, when RAID devices were created on top of storvsc devices. An upstream patch has been applied to fix this bug, and storvsc now returns the correct error code in the described situation. (BZ#1197749)
All kernel users are advised to upgrade to these updated packages, which contain backported patches to correct these issues. The system must be rebooted for this update to take effect.