RHBA-2016:0345 - Bug Fix Advisory

Topic

Updated kernel packages that fix several bugs are now available for Red Hat
Enterprise Linux 6.6 Extended Update Support.

Description

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

This update also fixes the following bugs:

• When removing a directory and 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#1282620)

• Previously, 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#1285692)

• Due to a race condition, the journal_remove_journal_head() function could

previously oops when trying to access journal_head returned by the bh2jh()
function. This update provides an upstream patch fixing this oops. (BZ#1291346)

• 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#1292081)

• 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 netpoll transmit
path, preventing kernel crashes in this situation.(BZ#1295368)

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 for x86_64 - Extended Update Support 6.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.6 i386
• Red Hat Enterprise Linux Server - AUS 6.6 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 6.6 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 6.6 ppc64
• Red Hat Enterprise Linux Server - TUS 6.6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.6 i386
• Red Hat Enterprise Linux EUS Compute Node 6.6 x86_64

Fixes

CVEs

(none)

References

(none)