linux-kernel - Re: [PATCH 2/2] x86/speculation: Provide application property based STIBP protection

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Message-ID: <a66fc9d3-db2d-a6b6-9f09-032597a8c3b0@linux.intel.com>
Date:   Thu, 20 Sep 2018 10:32:20 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
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 2/2] x86/speculation: Provide application property based
 STIBP protection

On 09/20/2018 01:00 AM, Peter Zijlstra wrote:
> On Wed, Sep 19, 2018 at 02:35:30PM -0700, Tim Chen wrote:
>> This patch provides an application property based spectre_v2
>> protection with STIBP against attack from another app from
>> a sibling hyper-thread.  For security sensitive non-dumpable
>> app, STIBP will be turned on before switching to it for Intel
>> processors vulnerable to spectre_v2.
> 
> Why does that non dumpable thing make sense? Why not use the same
> prctl() we already use for SSBD?
> 

Something like the following?

   prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_SPECTREV2_APP, 0, 0, 0);
   prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_SPECTREV2_APP, PR_SPEC_ENABLE, 0, 0);
   prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_SPECTREV2_APP, PR_SPEC_DISABLE, 0, 0);
   prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_SPECTREV2_APP, PR_SPEC_FORCE_DISABLE, 0, 0);

People may have already made changes to their app using non-dumpable to mitigate app-app
attack.  So I think we should still protect the non-dumpable processes so they don't
have to change their application code.

Tim