RHSA-2016:1406 - Security Advisory

Topic

Updated kernel packages that fix one security issue and several bugs are now available for Red Hat Enterprise Linux 6.

Red Hat Product Security has rated this update as having Important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section.

Description

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

Security Fix:

• A flaw was found in the way certain interfaces of the Linux kernel's Infiniband subsystem used write() as bi-directional ioctl() replacement, which could lead to insufficient memory security checks when being invoked using the the splice() system call. A local unprivileged user on a system with either Infiniband hardware present or RDMA Userspace Connection Manager Access module explicitly loaded, could use this flaw to escalate their privileges on the system. (CVE-2016-4565, Important)

Red Hat would like to thank Jann Horn for reporting this issue.

This update also fixes the following bugs:

• When providing some services and using the Integrated Services Digital Network (ISDN), the system could terminate unexpectedly due to the call of the tty_ldisc_flush() function. The provided patch removes this call and the system no longer hangs in the described scenario. (BZ#1337443)
• An update to the Red Hat Enterprise Linux 6.8 kernel added calls of two

functions provided by the ipv6.ko kernel module, which added a dependency on that module. On systems where ipv6.ko was prevented from being loaded, the nfsd.ko and lockd.ko modules were unable to be loaded. Consequently, it was not possible to run an NFS server or to mount NFS file systems as a client. The underlying source code has been fixed by adding the symbol_get() function, which determines if nfsd.ko and lock.ko are loaded into memory and calls them through function pointers, not directly. As a result, the aforementioned kernel modules are allowed to be loaded even if ipv6.ko is not, and the NFS mount works as expected. (BZ#1341496)

• After upgrading the kernel, CPU load average increased compared to the prior kernel version due to the modification of the scheduler. The provided patch set reverts the calculation algorithm of this load average to the the previous version thus resulting in relatively lower values under the same system load. (BZ#1343015)

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 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 - 1310570 - CVE-2016-4565 kernel: infiniband: Unprivileged process can overwrite kernel memory using rdma_ucm.ko

CVEs

• CVE-2016-4565

References

• http://www.redhat.com/security/updates/classification/#normal