linux-kernel - Re: [PATCH] mm/mincore: allow for making sys

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <nycvar.YFH.7.76.1901090326460.16954@cbobk.fhfr.pm>
Date:   Wed, 9 Jan 2019 03:31:35 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Dave Chinner <david@...morbit.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jann Horn <jannh@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>, Linux-MM <linux-mm@...ck.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

On Wed, 9 Jan 2019, Dave Chinner wrote:

> > But mincore is certainly the easiest interface, and the one that
> > doesn't require much effort or setup.
> 
> Off the top of my head, here's a few vectors for reading the page
> cache residency state without perturbing the page cache residency
> pattern:
> 	- mincore
> 	- preadv2(RWF_NOWAIT)
> 	- fadvise(POSIX_FADV_RANDOM); timed read(2) syscalls
> 	- madvise(MADV_RANDOM); timed read of first byte in each page

While I obviously agree that all those are creating pagecache sidechannel 
in principle, I think we really should mostly focus on the first two (with 
mincore() already having been covered).

Rationale has been provided by Daniel Gruss in this thread -- if the 
attacker is left with cache timing as the only available vector, he's 
going to be much more successful with mounting hardware cache timing 
attack anyway.

Thanks,

-- 
Jiri Kosina
SUSE Labs