qemu-kvm (SL6)

Synopsis: Important: qemu-kvm security update
Advisory ID: SLSA-2019:1181-1
Issue Date: 2019-05-14
CVE Numbers: CVE-2018-12126

Security Fix(es):

* 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. (CVE-2018-12130)

* 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 CPUs 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)

* 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.


– Scientific Linux Development Team