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

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Date:   Wed, 21 Nov 2018 14:29:29 -0800
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     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 11/20/2018 04:08 PM, Tim Chen wrote:

> From: Jiri Kosina <jkosina@...e.cz>
> 
> If 'prctl' mode of app2app protection from spectre_v2 is selected on
> kernel command-line, we are currently applying STIBP protection to
> tasks that restrict their indirect branch speculation via
> 
> 	prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0);
> 
> Let's extend this to cover also SECCOMP tasks (analogically to how we
> apply SSBD protection).
> 
> 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.
> 
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> ---

Will need this chunk added, which I missed in my update of Jiri's patch.

Thanks.

Tim

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c4d010d..d070e84 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -275,6 +275,7 @@ enum spectre_v2_app2app_cmd {
 	{ "off",	SPECTRE_V2_APP2APP_CMD_NONE,	false },
 	{ "on",		SPECTRE_V2_APP2APP_CMD_FORCE,	true  },
 	{ "prctl",	SPECTRE_V2_APP2APP_CMD_PRCTL,	false },
+	{ "seccomp",	SPECTRE_V2_APP2APP_CMD_SECCOMP,	false },
 };
 
 static void __init spec_v2_app_print_cond(const char *reason, bool secure)