RHBA-2016:2966 - Bug Fix Advisory

Topic

Updated kernel packages that fix several bugs and add various enhancements are now available for Red Hat Enterprise Linux 7.

Description

The kernel packages contain the Linux kernel, the core of any Linux
operating system.

This update fixes the following bugs:

• Previously, a "NULL pointer dereference" problem in the pick_next_task_fair() function occurred. This update fixes the bug by applying a set of patches on the Completely Fair Scheduler (CFS) group scheduling. As a result, the "NULL pointer dereference" problem no longer occurs. (BZ#1373820)
• When repetitively shutting down and powering on the Chrony Network Time Protocol (NTP) client, the following error occurred on the Hyper-V servers: "Adjusting Time Stamp Counter (TSC) more than 11%." This update limits the maximum adjustment cap in the internal steering to 11%, and the error no longer occurs under the described circumstances. (BZ#1375599)
• Previously, tasks writing to a NFS file in some cases became unresponsive, because they waited for the PG_BUSY flag to be cleared. This update fixes the problem by ignoring the zero-length requests at the page I/O layer. As a result, writing to affected NFS files now proceeds as expected. (BZ#1378916)
• Prior to this update, if a Red Hat Enterprise Linux 6 guest running on a Hyper-V hypervisor took a long time to boot, the hypervkvpd daemon in some cases failed to start. As a consequence, the guest could not use the services provided by these daemons, including online backup, file copy, and network settings. This update fixes the problem by refactoring the hv_util service corresponding to hypervkvpd. As a result, hypervkvpd starts properly in the described scenario, which makes the affected services available as expected regardless of the virtual machine's boot time. (BZ#1380305)
• In some cases, mounting a new file system to a slave mount tree caused the operating system to terminate unexpectedly. This update modifies handling of the mnt_group_id parameter in the propagate_one() function, and the operating system no longer crashes in the described situation. (BZ#1381319)
• Previously, an XFS metadata buffer reference counting race error sometimes caused soft lockups in the filesystem freeze path. For example, this problem occurred when creating device mapper snapshots. This update fixes the buffer reference counting, and all buffers are now reclaimed correctly during a filesystem freeze. As a result, the kernel soft lockup no longer occurs under the described circumstances. (BZ#1381563)
• Previously, changing the speed of a network device with the "ethtool -s" command in the mlx5 driver did not work correctly. Running the command switched the speed to unknown and caused mlx5 to become unresponsive. This update enforces the transition of the speed regardless of the port's current operation state. As a result, speed change of a network device in mlx5 now works as expected. (BZ#1385479)
• When rebinding a PF_PACKET socket with the same protocol and device as in the previous bind, the use count of the interface was not decreased. As a consequence, the deletion of the interface failed with the following error message: "unregister_netdevice: waiting for dummy0 to become free. Usage count = 1". This update removes the race condition in the packet_bind() function. As a result, the deletion of the interface now proceeds as expected, and the error message no longer occurs. (BZ#1388615)

All users are advised to upgrade to these updated packages, which fix these bugs and add these enhancements. The system must be rebooted for this update to take effect.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.2 x86_64
• Red Hat Enterprise Linux Server - AUS 7.2 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.2 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.2 ppc64
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.2 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.2 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.2 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.2 x86_64

Fixes

CVEs

(none)

References

(none)