Important kernel security update: Fixes for Meltdown and Spectre exploits; new kernel 2.6.32-042stab127.2, Virtuozzo 6.0 Update 12 Hotfix 20 (6.0.12-3690)

This update provides a new Virtuozzo 6.0 kernel 2.6.32-042stab127.2 that is a rebase to the Red Hat Enterprise Linux 6.9 kernel 2.6.32-696.18.7.el6. The rebase fixes an industry-wide issue that was found in the way many modern microprocessor designs have implemented speculative execution of instructions (a commonly used performance optimization). There are three primary variants of the issue which differ in the way the speculative execution can be exploited. NOTE: This issue is present in hardware and cannot be fully fixed via software update. The updated kernel packages provide software mitigation for this hardware issue at a cost of potential performance penalty. Please refer to References section for further information about this issue and the performance impact. In this update mitigations for x86-64 architecture are provided. The new kernel also introduces internal stability fixes.
Vulnerability id: CVE-2017-5715
CVE-2017-5715 triggers the speculative execution by utilizing branch target injection. It relies on the presence of a precisely-defined instruction sequence in the privileged code as well as the fact that memory accesses may cause allocation 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 cross the syscall and guest/host boundaries and read privileged memory by conducting targeted cache side-channel attacks.

Vulnerability id: CVE-2017-5753
CVE-2017-5753 triggers the speculative execution by performing a bounds-check bypass. It relies on the presence of a precisely-defined instruction sequence in the privileged code as well as the fact that memory accesses may cause allocation 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 cross the syscall boundary and read privileged memory by conducting targeted cache side-channel attacks.

Vulnerability id: CVE-2017-5754
CVE-2017-5754 relies on the fact that, on impacted microprocessors, during speculative execution of instruction permission faults, exception generation triggered by a faulting access is suppressed until the retirement of the whole instruction block. In a combination with the fact that memory accesses may populate the cache even when the block is being dropped and never committed (executed), an unprivileged local attacker could use this flaw to read privileged (kernel space) memory by conducting targeted cache side-channel attacks.