[$] More timing side-channels for the page cache

In 2019, researchers published a way to identify which file-backed pages were being accessed on a system using timing information from the page cache, leading to a handful of unpleasant consequences and a change to the design of the

mincore() system call. Discussion at the time led to a number of ad-hoc patches to address the problem. The lack of new page-cache attacks suggested that attempts to fix things in a piecemeal fashion had succeeded. Now, however, Sudheendra Raghav Neela, Jonas Juffinger, Lukas Maar, and Daniel Gruss have found a new set of holes in the Linux kernel's page-cache-timing protections that allow the same general class of attack.