The Spectre variant 2 vulnerability allows the speculative execution of incorrect (in an attacker-controllable way) indirect branch predictions, resulting in the ability to exfiltrate information via side channels. The kernel has been reasonably well protected against this variant since shortly after its disclosure in January. It is, however, possible for user-space processes to use Spectre v2 to attack each other; thus far, the mainline kernel has offered relatively little protection against such attacks. A recent proposal from Jiri Kosina may change that situation, but there are still some disagreements around the details.