Post Syndicated from original https://lwn.net/Articles/901834/

“Retbleed”
is the name given to a class of speculative-execution vulnerabilities
involving return instructions. Mitigations for Retbleed have found their
way into the mainline kernel but, as of this writing, some remaining
problems have kept them from the stable update releases. Mitigating
Retbleed can impede performance severely, especially on some Intel
processors. Thomas Gleixner and Peter Zijlstra think they have found a better
way that bypasses the existing mitigations and misleads the processor’s
speculative-execution mechanisms instead.