RHBA-2015:1992 - Bug Fix Advisory

Topic

Updated kernel packages that fix several bugs are now available for Red Hat
Enterprise Linux 6.

Description

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

This update fixes the following bugs:

• The memory used by the defragmentation engine is accounted for per CPU.

However, on systems with numerous CPUs, the per-CPU caches could deviate from
reality, thus causing the defragmentation engine to discard old fragments too
early. This update adds a fix to minimize this discrepancy, and old fragments
are now discarded in time. (BZ#1246088)

• Previously, reloading or removing edac modules on a system using the

i7core_edac module could lead to a number of returned warning messages and a
subsequent kernel crash. The underlying source code has been patched, and the
kernel no longer crashes when operating with edac modules. (BZ#1255492)

• Due to a regression, packets counter detected only the number of normally

processed completions (packets), not the erroneous ones. As these packets were
thus never acknowledged, the firmware kept returning interrupt requests (IRQs).
A patch has been provided to fix this bug, and all packets are now counted as
expected. (BZ#1260535)

• Unlikely conditions in the nfs_clear_inode() function can cause a kernel panic

due to the use of the BUG_ON() macro. An upstream patch replacing the BUG_ON()
macro with WARN_ON_ONCE() in this function has been provided to avoid this panic
and the kernel panic no longer occurs in this situation. (BZ#1266364)

• Previously, a bridge interface could exist on top of a bonded interface, which

was above a physical interface with the large receive offload (LRO) flag still
on. Bridge interfaces are incompatible with LRO enabled on any underlying
devices, which caused network communications on the bridge, such as that from a
Virtual Machine (VM) to fail to function properly. This update makes sure
devices underneath a bridge all get LRO disabled, and a VM now connects via a
bridged interface successfully. (BZ#1266366)

• During a KVM guest shutdown, if a virtio device generated interrupts, the

virtio driver sometimes could not correctly handle or clear the interrupt. As a
consequence, the system became busy, continuously processing the same interrupt,
leading to an incomplete shutdown of the KVM guest. This bug has been fixed, and
the guest now shuts down properly. (BZ#1266369)

• After adjusting the extent size with the xfs_fio utility and running the fio

command with the configuration file provided, the XFS file system became
corrupted. This update makes sure the extent size hints can round up extents
past the maximum extent length, and the XFS file system now preserves fio
operations. (BZ#1266372)

• At a process or thread exit, when the Linux kernel undoes any SysV semaphore

operations done previously (the ones done using semop with the SEM_UNDO flag),
there was a possible flaw and race with another process or thread removing the
same semaphore set where the operations occurred, leading to possible use of
in-kernel-freed memory and then to possible unpredictable behaviour. This bug
could be noticed with software which uses IPC SysV semaphores, such as IBM DB2,
which for example in certain cases could lead to a situation where its processes
or utilities could get incorrectly stalled in some IPC semaphore operation or
syscall after the race or problem happened. A patch has been provided to fix
this bug, and the kernel now behaves as expected in the aforementioned scenario.
(BZ#1266373).

• On a system with a bonded interface, the user could not specify a custom MAC

address for the bond. A patch has been provided to fix this bug, and custom MAC
addresses can be specified again in the aforementioned situation. (BZ#1266374)

Users of kernel are advised to upgrade to these updated packages. 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 Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.7 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 6.7 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 6.7 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.7 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.7 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux EUS Compute Node 6.7 x86_64
• Red Hat Enterprise Linux for SAP Solutions for x86_64 - Extended Update Support 6.7 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x

Fixes

CVEs

(none)

References

(none)