linux-kernel - Re: [Patch v6 12/16] x86/speculation: Add 'seccomp' Spectre v2 app to app protection mode

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Date:   Wed, 21 Nov 2018 01:44:41 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     Thomas Gleixner <tglx@...utronix.de>,
        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
Subject: Re: [Patch v6 12/16] x86/speculation: Add 'seccomp' Spectre v2 app
 to app protection mode

On Tue, 20 Nov 2018, Tim Chen wrote:

> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index d2255f7..89b193c 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4227,12 +4227,17 @@
>  				  and STIBP mitigations against Spectre V2 attacks.
>  				  If the CPU is not vulnerable, "off" is selected.
>  				  If the CPU is vulnerable, the default mitigation
> -				  is "prctl".
> +				  is architecture and Kconfig dependent. See below.
>  			prctl   - Enable mitigations per thread by restricting
>  				  indirect branch speculation via prctl.
>  				  Mitigation for a thread is not enabled by default to
>  				  avoid mitigation overhead. The state of
>  				  of the control is inherited on fork.
> +			seccomp - Same as "prctl" above, but all seccomp threads
> +				  will disable SSB unless they explicitly opt out.

As Dave already pointed out elsewhere -- the "SSB" here is probably a 
copy/paste error. It should read something along the lines of "... will 
restrict indirect branch speculation ..."

Thanks,

-- 
Jiri Kosina
SUSE Labs