Post Syndicated from corbet original https://lwn.net/Articles/940783/

There is a newly disclosed set of vulnerabilities in Intel processors that
have been given the name Downfall
attacks.

Downfall attacks targets a critical weakness found in billions of
modern processors used in personal and cloud computers. This
vulnerability, identified as CVE-2022-40982, enables a user to
access and steal data from other users who share the same
computer. For instance, a malicious app obtained from an app store
could use the Downfall attack to steal sensitive information like
passwords, encryption keys, and private data such as banking
details, personal emails, and messages. Similarly, in cloud
computing environments, a malicious customer could exploit the
Downfall vulnerability to steal data and credentials from other
customers who share the same cloud computer.

A series of patches has landed in the mainline kernel, including one for gather data sampling
mitigation and one to disable the AVX
extension on CPUs where microcode mitigation is not available.
“This is a *big* hammer. It is known to break buggy userspace that
uses incomplete, buggy AVX enumeration.”

Not to be left out, AMD processors suffer from a return-stack overflow
vulnerability, again exploitable via speculative execution; this patch, also just
merged, describes the problem and its mitigation.