linux-kernel - Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO)

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: <20171115145835.GB319@bombadil.infradead.org>
Date:   Wed, 15 Nov 2017 06:58:35 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Tycho Andersen <tycho@...ker.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, kernel-hardening@...ts.openwall.com,
        Marco Benatto <marco.antonio.780@...il.com>,
        Juerg Haefliger <juerg.haefliger@...onical.com>, x86@...nel.org
Subject: Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame
 Ownership (XPFO)

On Tue, Nov 14, 2017 at 11:00:20PM -0800, Dave Hansen wrote:
> On 11/14/2017 07:44 PM, Matthew Wilcox wrote:
> > We don't need to kmap in order to access MOVABLE allocations.  kmap is
> > only needed for HIGHMEM allocations.  So there's nothing wrong with ext4
> > or set_bh_page().
> 
> Yeah, it's definitely not _buggy_.
> 
> Although, I do wonder what we should do about these for XPFO.  Should we
> just stick a kmap() in there and comment it?  What we really need is a
> mechanism to say "use this as a kernel page" and "stop using this as a
> kernel page".  kmap() does that... kinda.  It's not a perfect fit, but
> it's pretty close.

It'd be kind of funny if getting XPFO working better means improving
how well Linux runs on 32-bit machines with HIGHMEM.  I think there's
always going to be interest in those -- ARM developed 36 bit physmem
before biting the bullet and going to arm64.  Maybe OpenRISC will do
that next ;-)