RHSA-2016:2766 - Security Advisory

Topic

An update for kernel is now available for Red Hat Enterprise Linux 6.

Red Hat Product Security has rated this update as having a security impact of Important. 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):

• It was found that stacking a file system over procfs in the Linux kernel could lead to a kernel stack overflow due to deep nesting, as demonstrated by mounting ecryptfs over procfs and creating a recursion by mapping /proc/environ. An unprivileged, local user could potentially use this flaw to escalate their privileges on the system. (CVE-2016-1583, Important)
• It was reported that on s390x, the fork of a process with four page table levels will cause memory corruption with a variety of symptoms. All processes are created with three level page table and a limit of 4TB for the address space. If the parent process has four page table levels with a limit of 8PB, the function that duplicates the address space will try to copy memory areas outside of the address space limit for the child process. (CVE-2016-2143, Moderate)

Bug Fix(es):

• Use of a multi-threaded workload with high memory mappings sometiems caused a kernel panic, due to a race condition between the context switch and the pagetable upgrade. This update fixes the switch_mm() by using the complete asce parameter instead of the asce_bits parameter. As a result, the kernel no longer panics in the described scenario. (BZ#1377472)
• When iptables created the Transmission Control Protocol (TCP) reset packet, a kernel crash could occur due to uninitialized pointer to the TCP header within the Socket Buffer (SKB). This update fixes the transport header pointer in TCP reset for both IPv4 and IPv6, and the kernel no longer crashes in the described situation.(BZ#1372266)
• Previously, when the Enhanced Error Handling (EEH) mechanism did not block the PCI configuration space access and an error was detected, a kernel panic occurred. This update fixes EEH to fix this problem. As a result, the kernel no longer panics in the described scenario. (BZ#1379596)
• When the lockd service failed to start up completely, the notifier blocks were in some cases registered on a notification chain multiple times, which caused the occurrence of a circular list on the notification chain. Consequently, a soft lock-up or a kernel oops occurred. With this update, the notifier blocks are unregistered if lockd fails to start up completely, and the soft lock-ups or the kernel oopses no longer occur under the described circumstances. (BZ#1375637)
• When the Fibre Channel over Ethernet (FCoE) was configured, the FCoE MaxFrameSize parameter was incorrectly restricted to 1452. With this update, the NETIF_F_ALL_FCOE symbol

is no longer ignored, which fixes this bug. MaxFrameSize is now restricted to 2112, which is the correct value. (BZ#1381592)

• When the fnic driver was installed on Cisco UCS Blade Server, the discs were under certain circumstances put into the offline state with the following error message: "Medium access timeout failure. Offlining disk!". This update fixes fnic to set the Small Computer System Interface (SCSI) status as DID_ABORT after a successful abort operation. As a result, the discs are no longer put into the offlined state in the described situation. (BZ#1382620)

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 6 x86_64
• Red Hat Enterprise Linux Server 6 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 Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x

Fixes

• BZ - 1308908 - CVE-2016-2143 kernel: Fork of large process causes memory corruption
• BZ - 1344721 - CVE-2016-1583 kernel: Stack overflow via ecryptfs and /proc/$pid/environ

CVEs

• CVE-2016-1583
• CVE-2016-2143

References

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