Advisories » MGASA-2019-0174

Updated kernel packages fix security vulnerability

Publication date: 16 May 2019
Type: security
Affected Mageia releases : 6
CVE: CVE-2018-12126 , CVE-2018-12127 , CVE-2018-12130 , CVE-2019-11091


This kernel update provides the upstream 4.14.119 that adds the kernel side
mitigations for the Microarchitectural Data Sampling (MDS, also called
ZombieLoad attack) vulnerabilities in Intel processors that can allow
attackers to retrieve data being processed inside a CPU. To complete the
mitigations new microcode is also needed, either by installing the
microcode-0.20190514-1.mga6 package, or get an updated bios / uefi
firmware from the motherboard vendor.

The fixed / mitigated issues are:

Modern Intel microprocessors implement hardware-level micro-optimizations
to improve the performance of writing data back to CPU caches. The write
operation is split into STA (STore Address) and STD (STore Data)
sub-operations. These sub-operations allow the processor to hand-off
address generation logic into these sub-operations for optimized writes.
Both of these sub-operations write to a shared distributed processor
structure called the 'processor store buffer'. As a result, an
unprivileged attacker could use this flaw to read private data resident
within the CPU's processor store buffer. (CVE-2018-12126)

Microprocessors use a ‘load port’ subcomponent to perform load operations
from memory or IO. During a load operation, the load port receives data
from the memory or IO subsystem and then provides the data to the CPU
registers and operations in the CPU’s pipelines. Stale load operations
results are stored in the 'load port' table until overwritten by newer
operations. Certain load-port operations triggered by an attacker can be
used to reveal data about previous stale requests leaking data back to the
attacker via a timing side-channel. (CVE-2018-12127)

A flaw was found in the implementation of the "fill buffer", a mechanism
used by modern CPUs when a cache-miss is made on L1 CPU cache. If an
attacker can generate a load operation that would create a page fault,
the execution will continue speculatively with incorrect data from the
fill buffer while the data is fetched from higher level caches. This
response time can be measured to infer data in the fill buffer.

Uncacheable memory on some microprocessors utilizing speculative execution
may allow an authenticated user to potentially enable information disclosure
via a side channel with local access. (CVE-2019-11091)