RHBA-2015:1689 - 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 fixes the following bugs:

• If a server returned an empty or malformed READDIR response, the NFS client

could previously terminate unexpectedly while attempting to decode that
response. This update uses the response size to determine if existing pages of
data are available for decoding, and the client only decodes the responses if
they exist. As a result, the NFS client no longer attempts to decode pages of
data that may not exist, and the aforementioned crash is thus avoided.
(BZ#1231075)

• Due to the need to initialize the memory block and create the sysfs file

system entries, the memory_dev_init() function previously took a very long time
to finish its task on systems with a high number of memory blocks. An upstream
patch has been applied to enhance memory_dev_init() so that memory
initialization proceeds in a more timely manner. (BZ#1231643)

• Due to bad memory or memory corruption, an isolated BUG_ON(mm->nr_ptes) was

sometimes reported, indicating that not all the page tables allocated could be
found and freed when the exit_mmap() function cleared the user address space. As
a consequence, a kernel panic occurred. To fix this bug, the BUG_ON() function
has been replaced by WARN_ON(), which prevents the kernel from panicking in the
aforementioned situation. (BZ#1235931)

• 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#1243397)

• Due to the broken s_umount lock ordering, a race condition occurred when an

unlinked file was closed and the sync (or syncfs) utility was run at the same
time. As a consequence, deadlock occurred on a frozen file system between sync
and a process trying to unfreeze the file system. With this update, sync (or
syncfs) is skipped on a frozen file system, and deadlock no longer occurs in the
aforementioned situation. (BZ#1243402)

• Previously, in the scenario when a file was opened by file handle (fhandle)

with its dentry not present in dcache ("cold dcache") and then making use of the
unlink() and close() functions, the inode was not freed upon the close() system
call. As a consequence, the final iput() was delayed indefinitely. A patch has
been provided to fix this bug, and the inode is now freed as expected.
(BZ#1243405)

All users 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

• BZ - 1230291 - Block stats broken, using non-atomic inflight counter. [rhel-6.6.z]

CVEs

(none)

References

(none)