kernel: Indirect branch speculation can be enabled after it was force-disabled by the PR_SPEC_FORCE_DISABLE prctl command.

A flaw was found in the prctl function, where it can be used to enable indirect branch speculation after it has been disabled. This call incorrectly reports it as being 'force disabled' when it is not and opens the system to Spectre v2 attacks. The highest threat from this vulnerability is to...