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Date:   Fri, 1 Feb 2019 10:11:52 +0100
From:   Michal Hocko <mhocko@kernel.org>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-api@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Jann Horn <jannh@google.com>, Jiri Kosina <jikos@kernel.org>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Dave Chinner <david@fromorbit.com>,
        Kevin Easton <kevin@guarana.org>,
        Matthew Wilcox <willy@infradead.org>,
        Cyril Hrubis <chrubis@suse.cz>, Tejun Heo <tj@kernel.org>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Daniel Gruss <daniel@gruss.cc>, Jiri Kosina <jkosina@suse.cz>,
        Josh Snyder <joshs@netflix.com>
Subject: Re: [PATCH 3/3] mm/mincore: provide mapped status when cached status
 is not allowed
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On Fri 01-02-19 10:04:23, Vlastimil Babka wrote:
> 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. You shouldn't be able to sniff on
/proc/$vicimt/smaps as an attacker.
-- 
Michal Hocko
SUSE Labs