On 2/1/19 10:11 AM, Michal Hocko wrote:

On Fri 01-02-19 10:04:23, Vlastimil Babka wrote:

quoted

The side channel exists anyway as long as process can e.g. check if
its rss shrinked, and I doubt we are going to remove that possibility.

Well, but rss update will not tell you that the page has been faulted in
which is the most interesting part.

Sure, but the patch doesn't add back that capability neither. It allows
to recognize page being reclaimed, and I argue you can infer that from
rss change as well. That change is mentioned in the last paragraph in
changelog, and I thought "add a hard to evaluate side channel" in your
reply referred to that. It doesn't add back the "original" side channel
to detect somebody else accessed a page.

You shouldn't be able to sniff on
/proc/$vicimt/smaps as an attacker.