linux-kernel - Re: [RFC v2 00/27] Kernel Address Space Isolation

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Message-ID: <20190712190620.GX3419@hirez.programming.kicks-ass.net>
Date:   Fri, 12 Jul 2019 21:06:20 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Dave Hansen <dave.hansen@...el.com>, pbonzini@...hat.com,
        rkrcmar@...hat.com, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org, kvm@...r.kernel.org,
        x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        konrad.wilk@...cle.com, jan.setjeeilers@...cle.com,
        liran.alon@...cle.com, jwadams@...gle.com, graf@...zon.de,
        rppt@...ux.vnet.ibm.com, Paul Turner <pjt@...gle.com>
Subject: Re: [RFC v2 00/27] Kernel Address Space Isolation

On Fri, Jul 12, 2019 at 06:37:47PM +0200, Alexandre Chartre wrote:
> On 7/12/19 5:16 PM, Thomas Gleixner wrote:

> > Right. If we decide to expose more parts of the kernel mappings then that's
> > just adding more stuff to the existing user (PTI) map mechanics.
> 
> If we expose more parts of the kernel mapping by adding them to the existing
> user (PTI) map, then we only control the mapping of kernel sensitive data but
> we don't control user mapping (with ASI, we exclude all user mappings).
> 
> How would you control the mapping of userland sensitive data and exclude them
> from the user map? Would you have the application explicitly identify sensitive
> data (like Andy suggested with a /dev/xpfo device)?

To what purpose do you want to exclude userspace from the kernel
mapping; that is, what are you mitigating against with that?