Moderate: kernel security and bug fix update

Synopsis

Moderate: kernel security and bug fix update

Type/Severity

Security Advisory: Moderate

Topic

An update for kernel is now available for Red Hat Enterprise Linux 7.4 Extended Update Support.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

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

Security Fix(es):

• kernel: userfaultfd bypasses tmpfs file permissions (CVE-2018-18397)
  

For more details about the security issue(s), including the impact, a CVSS score, and other related information, refer to the CVE page(s) listed in the References section.

Bug Fix(es):

• The timeout handling in the libfc.ko kernel module did not work correctly. This was happening during certain steps of the Fibre Channel login procedure, when the timeout handling was not synchronized with the state of a partially offloaded Fibre Channel over Ethernet (FCoE) in the lower-level driver. Consequently, the offloaded FCoE state was incorrect, which led to I/O timeout errors until the SCSI error recovery issued a host reset. This update fixes the bug by improving the libfc.ko error handling during the fabric login. As a result, the fabric login errors are addressed in time, without the I/O timeouts in the described scenario. (BZ#1655042)
  
• Symmetric Multi-Processing (SMP) or Non-Uniform Memory Access (NUMA) systems in some cases experienced deadlocks during a task migration and task wakeup operations. Consequently, the systems terminated unexpectedly with the following message:
  

NMI watchdog: Watchdog detected hard LOCKUP on

This update fixes the bug by queueing the stopper thread to run after locks are released. As a result, the deadlocks and the system crashes no longer occur in the described scenario. (BZ#1667326)

Users of kernel are advised to upgrade to these updated packages, which fix these bugs.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.

Affected Products

• Red Hat Enterprise Linux Server - Extended Update Support 7.4 x86_64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.4 ppc64
• Red Hat Enterprise Linux EUS Compute Node 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.4 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.4 s390x
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.4 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.4 x86_64
• Red Hat Enterprise Linux Server (for IBM Power LE) - Update Services for SAP Solutions 7.4 ppc64le
• Red Hat Enterprise Linux Server - Update Services for SAP Solutions 7.4 x86_64

Fixes

• BZ - 1641548 - CVE-2018-18397 kernel: userfaultfd bypasses tmpfs file permissions

CVEs

• CVE-2018-18397

References

• https://access.redhat.com/security/updates/classification/#moderate