RHBA-2016:0150 - 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:

• Attempting to use the request_key() function to add a key into a revoked

keyring was causing a resource leak in the kernel error path. Keys which were
allocated and then failed became stuck in memory and were impossible for the
garbage collector to remove. With this update, the reference count on failed
keys correctly reaches 0 in this situation, allowing the garbage collector to
remove them. (BZ#1288095)

• A bug in the ipr driver on IBM Power Systems (ppc64) could result in backwards

memory buffer indexing and cause a kernel crash when running the Hardware Test
Exerciser (HTX) test suite. With this update, ipr memory buffer indexing uses a
bit mask operation instead of modulo, causing low bits to be masked off so that
backwards indexing is no longer possible. (BZ#1280211)

• Resetting an ixgbe or vmxnet3 adapter while sending a message over netconsole

or netpoll at the same time could previously cause a kernel crash. This update
adds mutual exclusion between the core adapter reset path and the netpoll
transmit path, and the crash no longer occurs. (BZ#1295370)

• When removing a directory while a reference was held to that directory by a

reference to a negative child dentry, the directory dentry was previously not
killed. In addition, once the negative child dentry was killed, unlinked and
unused dentry was present in the cache. As a consequence, deadlock could be
caused by forcing the dentry eviction while the file system in question was
frozen. With this update, all unused dentries are unhashed and evicted just
after a successful directory removal, which avoids the deadlock, and the system
no longer hangs in the aforementioned scenario. (BZ#1282621)

• Previously, an unusual forking pattern could cause the anon_vma_chain and

anon_vma slab memory to grow infinitely even though the number of processes
involved stayed low. As a consequence, a kernel panic occurred. The provided
patch adds a heuristic which reuses existing anon_vma instead of forking a new
one and adds the anon_vma->degree counter which makes sure the count of
anon_vmas is not bigger than twice the count of vmas. As a result, the kernel
panic no longer occurs in this situation. (BZ#1285693)

• A race condition was found in hash table invalidation code between inode

invalidation and inode clearing code in the GFS2 file system. In some
circumstances, two processes could attempt to free the same memory, resulting in
a kernel panic. This update adds a "spin_lock" to the hash table invalidation
code allowing only a single process to attempt to free a specific memory page,
which prevents the race condition from occurring. (BZ#1288093)

• Due to a timer expiry issue, the scheduler tick previously stopped for too

long when the ksoftirqd daemon for hrtimer was blocked by a running process.
This update adds the force_hrtimer_reprogram kernel parameter. If
"force_hrtimer_reprogram=1" is used on the kernel command line, the
reprogramming of all expired timers is forced, which prevents this bug.
(BZ#1292082)

• The kernel was incorrectly assigning multicast groups for the nl80211

protocol, causing problems with nl80211 wireless drivers. For example,
preventing hostapd from starting and initializing wireless devices in Access
Point mode. This update fixes multicast group assignments for nl80211 and allows
wireless devices to be managed correctly. (BZ#1259870)

• Large Receive Offload (LRO) flag disabling was not being propagated downwards

from above devices in vlan and bond hierarchy, breaking the flow of traffic.
This problem has been fixed and LRO flags now propagate correctly. (BZ#1259008)

Users of kernel are advised to upgrade to these updated packages, which fix
these bugs. 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 Server - Extended Life Cycle Support 6 i386
• 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 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
• 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 EUS Compute Node 6.7 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support Extension (for IBM z Systems) 6 s390x

Fixes

CVEs

(none)

References

(none)