RHBA-2017:3089 - Bug Fix Advisory

Topic

Updated kernel packages that fix five bugs 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, the bonding driver incorrectly renamed the symlinks referencing bonded devices in the sysfs pseudo filesystem. Consequently, the Application Binary Interface (ABI) exported to userspace and customer's scripts were broken. This update fixes the bonding driver to restore old symlink names in sysfs. As a result, ABI is no longer broken, and scripts using symlinks to bonded devices now work as expected. (BZ#1471679)
• Previously, the 'stack:TID' annotation was applied to correctly mark the thread stack in a /proc/<pid>/maps file and it required processing the entire thread list to find the task of a stack Virtual Memory Area (VMA). Consequently, rendering and accessing /proc/<pid>/maps took a long time

on systems with a large number of threads running. This update removes the annotation to make the /proc/<pid>/maps and /proc/<pid>/numa_maps files usable for higher thread counts. As a result, the system performance while rendering and accessing /proc/<pid>/maps has improved significantly (BZ#1481723)

• Previously, the debugging information for the cifs module could not be printed due to a regression in Red Hat Enterprise Linux 7.3. This update fixes the regression. With the new kernel, the cifs module uses the dynamic debugging facility available in the Linux kernel, which allows better control on which debugging content is printed. To enable debugging for the entire cifs module, use the following command in addition to the commands used to enable cifs debugging:

echo ´module cifs +p´ >/sys/kernel/debug/dynamic_debug/control
(BZ#1484266)

• If an NFS client with TCP time stamps disabled initiated a TCP disconnect sequence, the NFS TCP connection waited 60 seconds during the TIME_WAIT state because the source TCP port could not be re-used. Consequently, multiple side-effects could occur during the 60 second period. These side effects included unresponsive NFS mount points, an rpciod kernel thread consuming 100% CPU, the "retrans" number of "nfsstat -r" becoming a very large number or "not responding" and I/O errors at NFS mounts with low values of 'timeo' and 'retrans'. With this update, the NFS client selects a different source port when the NFS TCP connection needs to reconnect during the TIME_WAIT status. As a result, the NFS TCP connection now reconnects immediately after a disconnect sequence without waiting 60 seconds for TIME_WAIT to complete. (BZ#1484268)
• Previously, the value of the sg_tablesize variable, which represents the maximum allowable number of requests in the scatter-gather list, was calculated incorrectly for devices that can register page list bigger than 65536. Consequently, the performance of such devices was suboptimal. This update removes the wrong sg_tablesize assignment, and uses the value that was set during address resolution handling. As a result, performance issues no longer occur in the described situation. (BZ#1487608)

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 7.3 x86_64
• Red Hat Enterprise Linux Server - AUS 7.3 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.3 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.3 ppc64
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.3 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.3 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.3 x86_64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.3 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.3 x86_64

Fixes

CVEs

(none)

References

(none)