A logic bug flaw was found in Linux kernel before 5.8-rc1 in the
implementation of SSBD. A bug in the logic handling allows an attacker with
a local account to disable SSBD protection during a context switch when
additional speculative execution mitigations are in place. This issue was
introduced when the per task/process conditional STIPB switching was added
on top of the existing SSBD switching. The highest threat from this
vulnerability is to confidentiality.

It was discovered that the Linux kernel did not correctly apply Speculative
Store Bypass Disable (SSBD) mitigations in certain situations. A local
attacker could possibly use this to expose sensitive information.