Red Hat Enterprise Linux 6 RHSA-2018:2390 Important: Kernel Security

The kernel packages contain the Linux kernel, the core of any Linux operating system.
Security Fix(es):
* Modern operating systems implement virtualization of physical memory to efficiently use available system resources and provide inter-domain protection through access control and isolation. The L1TF issue was found in the way the x86 microprocessor designs have implemented speculative execution of instructions (a commonly used performance optimisation) in combination with handling of page-faults caused by terminated virtual to physical address resolving process. As a result, an unprivileged attacker could use this flaw to read privileged memory of the kernel or other processes and/or cross guest/host boundaries to read host memory by conducting targeted cache side-channel attacks. (CVE-2018-3620, CVE-2018-3646)
* An industry-wide issue was found in the way many modern microprocessor designs have implemented speculative execution of instructions past bounds check. The flaw relies on the presence of a precisely-defined instruction sequence in the privileged code and the fact that memory writes occur to an address which depends on the untrusted value. Such writes cause an update into the microprocessor's data cache even for speculatively executed instructions that never actually commit (retire). As a result, an unprivileged attacker could use this flaw to influence speculative execution and/or read privileged memory by conducting targeted cache side-channel attacks. (CVE-2018-3693)
* kernel: kvm: vmx: host GDT limit corruption (CVE-2018-10901)
* kernel: Use-after-free in snd_pcm_info function in ALSA subsystem potentially leads to privilege escalation (CVE-2017-0861)
* kernel: Use-after-free in snd_seq_ioctl_create_port() (CVE-2017-15265)
* kernel: race condition in snd_seq_write() may lead to UAF or OOB-access (CVE-2018-7566)
* kernel: Race condition in sound system can lead to denial of service (CVE-2018-1000004)
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.
Red Hat would like to thank Intel OSSIRT (Intel.com) for reporting CVE-2018-3620 and CVE-2018-3646; Vladimir Kiriansky (MIT) and Carl Waldspurger (Carl Waldspurger Consulting) for reporting CVE-2018-3693; and Vegard Nossum (Oracle Corporation) for reporting CVE-2018-10901.
Bug Fix(es):
* The Least recently used (LRU) operations are batched by caching pages in per-cpu page vectors to prevent contention of the heavily used lru_lock spinlock. The page vectors can hold even the compound pages. Previously, the page vectors were cleared only if they were full. Subsequently, the amount of memory held in page vectors, which is not reclaimable, was sometimes too high. Consequently the page reclamation started the Out of Memory (OOM) killing processes. With this update, the underlying source code has been fixed to clear LRU page vectors each time when a compound page is added to them. As a result, OOM killing processes due to high amounts of memory held in page vectors no longer occur. (BZ#1575819)