linux-kernel - Re: [Patch v7 14/18] x86/speculation: Add 'seccomp' Spectre v2 app to app protection mode

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Message-ID: <alpine.DEB.2.21.1811211451250.1665@nanos.tec.linutronix.de>
Date:   Wed, 21 Nov 2018 14:52:40 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     Jiri Kosina <jikos@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        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>,
        Waiman Long <longman9394@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Stewart <david.c.stewart@...el.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        stable@...r.kernel.org, Jiri Kosina <jkosina@...e.cz>
Subject: Re: [Patch v7 14/18] x86/speculation: Add 'seccomp' Spectre v2 app
 to app protection mode

On Tue, 20 Nov 2018, Tim Chen wrote:
> According to software guidance:
> 
> "Setting ... STIBP ... on a logical processor prevents the predicted
> targets of indirect branches on any logical processor of that core
> from being controlled by software that executes (or executed
> previously) on another logical processor of the same core."
> 
> https://software.intel.com/security-software-guidance/insights/deep-dive-single-thread-indirect-branch-predictors
> 
> Hence setting STIBP on a sandboxed task will prevent the task
> from attacking other sibling threads or getting attacked.

That's not sufficient, because you need an IBPB when the sandboxed task is
switched out.

Thanks,

	tglx