linux-kernel - Re: [Patch v3 00/13] Provide process property based options to enable Spectre v2 userspace-userspace protection

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Message-ID: <20181019183841.GB31016@hirez.programming.kicks-ass.net>
Date:   Fri, 19 Oct 2018 20:38:41 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: Re: [Patch v3 00/13] Provide process property based options to
 enable Spectre v2 userspace-userspace protection

On Fri, Oct 19, 2018 at 09:43:35AM -0700, Tim Chen wrote:
> On 10/19/2018 12:57 AM, Peter Zijlstra wrote:
> > On Wed, Oct 17, 2018 at 10:59:28AM -0700, Tim Chen wrote:
> >> Application to application exploit is in general difficult due to address
> >> space layout randomization in applications and the need to know an
> > 
> > Does the BTB attack on KASLR not work for userspace?
> > 
> 
> With KASLR, you can probe the kernel mapped and unmapped
> addresses with side channels like TLB and infer the kernel mapping
> offsets much more easily, as kernel is in the same address
> space as the attack process.  It is a lot harder to do
> such probing from another process that doesn't share the
> same page tables.

I said BTB; see: http://www.cs.binghamton.edu/~dima/micro16.pdf

>From what I understood, local ASLR (of any kind) is a pipe dream.