From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 822B3C2BC61 for ; Tue, 30 Oct 2018 21:34:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C2292081B for ; Tue, 30 Oct 2018 21:34:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C2292081B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727547AbeJaG3x (ORCPT ); Wed, 31 Oct 2018 02:29:53 -0400 Received: from mga04.intel.com ([192.55.52.120]:2367 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725743AbeJaG3x (ORCPT ); Wed, 31 Oct 2018 02:29:53 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Oct 2018 14:34:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,446,1534834800"; d="scan'208";a="104625428" Received: from schen9-desk.jf.intel.com (HELO [10.54.74.144]) ([10.54.74.144]) by orsmga002.jf.intel.com with ESMTP; 30 Oct 2018 14:34:44 -0700 Subject: Re: [Patch v4 16/18] x86/speculation: Enable STIBP to protect security sensitive tasks To: "Schaufler, Casey" , Jiri Kosina , Thomas Gleixner Cc: Tom Lendacky , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Andi Kleen , "Hansen, Dave" , "Mallick, Asit K" , Arjan van de Ven , Jon Masters , Waiman Long , "linux-kernel@vger.kernel.org" , "x86@kernel.org" References: <26ec186930a8fb33033743997bd56e5ce44050ec.1540923609.git.tim.c.chen@linux.intel.com> <99FC4B6EFCEFD44486C35F4C281DC6732148DC8C@ORSMSX110.amr.corp.intel.com> From: Tim Chen Openpgp: preference=signencrypt Autocrypt: addr=tim.c.chen@linux.intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <99FC4B6EFCEFD44486C35F4C281DC6732148DC8C@ORSMSX110.amr.corp.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/30/2018 02:07 PM, Schaufler, Casey wrote: >> -----Original Message----- >> From: Tim Chen [mailto:tim.c.chen@linux.intel.com] >> Sent: Tuesday, October 30, 2018 11:49 AM >> To: Jiri Kosina ; Thomas Gleixner >> Cc: Tim Chen ; Tom Lendacky >> ; Ingo Molnar ; Peter >> Zijlstra ; Josh Poimboeuf ; >> Andrea Arcangeli ; David Woodhouse >> ; Andi Kleen ; Hansen, Dave >> ; Schaufler, Casey ; >> Mallick, Asit K ; Arjan van de Ven >> ; Jon Masters ; Waiman Long >> ; linux-kernel@vger.kernel.org; x86@kernel.org >> Subject: [Patch v4 16/18] x86/speculation: Enable STIBP to protect security >> sensitive tasks >> >> Enable STIBP defense on high security tasks. >> >> For normal tasks, STIBP is unused so they are not impacted by overhead >> from STIBP in lite protection mode. >> >> Signed-off-by: Tim Chen >> --- >> arch/x86/kernel/cpu/bugs.c | 33 +++++++++++++++++++++++++++++++++ >> 1 file changed, 33 insertions(+) >> >> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c >> index 54f4675..b402b96 100644 >> --- a/arch/x86/kernel/cpu/bugs.c >> +++ b/arch/x86/kernel/cpu/bugs.c >> @@ -14,6 +14,8 @@ >> #include >> #include >> #include >> +#include >> +#include >> >> #include >> #include >> @@ -770,6 +772,37 @@ static int ssb_prctl_set(struct task_struct *task, >> unsigned long ctrl) >> return 0; >> } >> >> +static void set_task_stibp(struct task_struct *tsk, bool stibp_on) >> +{ >> + bool update = false; >> + >> + if (!static_branch_unlikely(&spectre_v2_app_lite)) >> + return; >> + >> + if (stibp_on) >> + update = !test_and_set_tsk_thread_flag(tsk, TIF_STIBP); >> + else >> + update = test_and_clear_tsk_thread_flag(tsk, TIF_STIBP); >> + >> + if (!update) >> + return; >> + >> + if (tsk == current) >> + speculation_ctrl_update_current(); >> +} >> + >> +void arch_set_security(struct task_struct *tsk, unsigned int value) > > In this context "security" isn't descriptive. arch_set_stibp_defenses() > would be better. A more generic name decoupled from STIBP will be preferable. There can other kind of security defenses to be erected in the future. Perhaps arch_set_mitigation? Thanks. Tim > > Since "value" should only ever have one of two values, and those > map directly to "true" or "false" this should be a bool, making the > code trivial: > > void arch_set_stibp_defenses(struct task_struct *task, bool stibp) > { > set_task_stibp(task, stibp); > } > > Or perhaps arch_set_security() should go away, and the calling > code would call set_task_stibp() directly. Unless there is some compelling > reason for the abstractions. > >> +{ >> + if (value > SECURITY_HIGH) >> + return; >> + >> + /* Update STIBP defenses */ >> + if (value == SECURITY_HIGH) >> + set_task_stibp(tsk, true); >> + else >> + set_task_stibp(tsk, false); >> +} >> + >> int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, >> unsigned long ctrl) >> { >> -- >> 2.9.4 >