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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 F09E2C43441 for ; Wed, 21 Nov 2018 20:18:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B50F1214DA for ; Wed, 21 Nov 2018 20:18:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B50F1214DA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de 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 S2389465AbeKVGyV (ORCPT ); Thu, 22 Nov 2018 01:54:21 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:45437 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389441AbeKVGyU (ORCPT ); Thu, 22 Nov 2018 01:54:20 -0500 Received: from localhost ([127.0.0.1] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1gPYxB-0000LX-0r; Wed, 21 Nov 2018 21:18:29 +0100 Message-Id: <20181121201724.414692525@linutronix.de> User-Agent: quilt/0.65 Date: Wed, 21 Nov 2018 21:14:52 +0100 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, Peter Zijlstra , Andy Lutomirski , Linus Torvalds , Jiri Kosina , Tom Lendacky , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , Waiman Long , Greg KH , Dave Stewart , Kees Cook , Tim Chen Subject: [patch 22/24] x86/speculation: Create PRCTL interface to restrict indirect branch speculation References: <20181121201430.559770965@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=x86-speculation-Create-PRCTL-interface-to-restrict-indirect-branch-speculation.patch Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tim Chen Add the PR_SPEC_INDIR_BRANCH option for the PR_GET_SPECULATION_CTRL and PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of indirect branch speculation via STIBP. Invocations: Check indirect branch speculation status with - prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, 0, 0, 0); Enable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0); Disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_DISABLE, 0, 0); Force disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0); See Documentation/userspace-api/spec_ctrl.rst. Signed-off-by: Tim Chen Signed-off-by: Thomas Gleixner --- Documentation/userspace-api/spec_ctrl.rst | 9 +++ arch/x86/include/asm/nospec-branch.h | 1 arch/x86/kernel/cpu/bugs.c | 71 ++++++++++++++++++++++++++++++ include/linux/sched.h | 9 +++ include/uapi/linux/prctl.h | 1 tools/include/uapi/linux/prctl.h | 1 6 files changed, 92 insertions(+) --- a/Documentation/userspace-api/spec_ctrl.rst +++ b/Documentation/userspace-api/spec_ctrl.rst @@ -92,3 +92,12 @@ Speculation misfeature controls * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_ENABLE, 0, 0); * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_DISABLE, 0, 0); * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_STORE_BYPASS, PR_SPEC_FORCE_DISABLE, 0, 0); + +- PR_SPEC_INDIR_BRANCH: Indirect Branch Speculation in User Processes + (Mitigate Spectre V2 style attacks against user processes) + + Invocations: + * prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, 0, 0, 0); + * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_ENABLE, 0, 0); + * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_DISABLE, 0, 0); + * prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIR_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0); --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -232,6 +232,7 @@ enum spectre_v2_mitigation { enum spectre_v2_app2app_mitigation { SPECTRE_V2_APP2APP_NONE, SPECTRE_V2_APP2APP_STRICT, + SPECTRE_V2_APP2APP_PRCTL, }; /* The Speculative Store Bypass disable variants */ --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -567,6 +567,8 @@ void arch_smt_update(void) case SPECTRE_V2_APP2APP_STRICT: update_stibp_strict(); break; + case SPECTRE_V2_APP2APP_PRCTL: + break; } mutex_unlock(&spec_ctrl_mutex); @@ -753,12 +755,56 @@ static int ssb_prctl_set(struct task_str return 0; } +static int indir_branch_prctl_set(struct task_struct *task, unsigned long ctrl) +{ + switch (ctrl) { + case PR_SPEC_ENABLE: + if (spectre_v2_app2app == SPECTRE_V2_APP2APP_NONE) + return 0; + /* + * Indirect branch speculation is always disabled in strict + * mode. + */ + if (spectre_v2_app2app == SPECTRE_V2_APP2APP_STRICT) + return -EPERM; + task_clear_spec_indir_branch_disable(task); + task_update_spec_tif(task, TIF_SPEC_IB, false); + break; + case PR_SPEC_DISABLE: + /* + * Indirect branch speculation is always allowed when + * mitigation is force disabled. + */ + if (spectre_v2_app2app == SPECTRE_V2_APP2APP_NONE) + return -EPERM; + if (spectre_v2_app2app == SPECTRE_V2_APP2APP_STRICT) + return 0; + task_set_spec_indir_branch_disable(task); + task_update_spec_tif(task, TIF_SPEC_IB, true); + break; + case PR_SPEC_FORCE_DISABLE: + if (spectre_v2_app2app == SPECTRE_V2_APP2APP_NONE) + return -EPERM; + if (spectre_v2_app2app == SPECTRE_V2_APP2APP_STRICT) + return 0; + task_set_spec_indir_branch_disable(task); + task_set_spec_indir_branch_force_disable(task); + task_update_spec_tif(task, TIF_SPEC_IB, true); + break; + default: + return -ERANGE; + } + return 0; +} + int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, unsigned long ctrl) { switch (which) { case PR_SPEC_STORE_BYPASS: return ssb_prctl_set(task, ctrl); + case PR_SPEC_INDIR_BRANCH: + return indir_branch_prctl_set(task, ctrl); default: return -ENODEV; } @@ -791,11 +837,34 @@ static int ssb_prctl_get(struct task_str } } +static int indir_branch_prctl_get(struct task_struct *task) +{ + if (!boot_cpu_has_bug(X86_BUG_SPECTRE_V2)) + return PR_SPEC_NOT_AFFECTED; + + switch (spectre_v2_app2app) { + case SPECTRE_V2_APP2APP_NONE: + return PR_SPEC_ENABLE; + case SPECTRE_V2_APP2APP_PRCTL: + if (task_spec_indir_branch_force_disable(task)) + return PR_SPEC_PRCTL | PR_SPEC_FORCE_DISABLE; + if (test_tsk_thread_flag(task, TIF_SPEC_IB)) + return PR_SPEC_PRCTL | PR_SPEC_DISABLE; + return PR_SPEC_PRCTL | PR_SPEC_ENABLE; + case SPECTRE_V2_APP2APP_STRICT: + return PR_SPEC_DISABLE; + default: + return PR_SPEC_NOT_AFFECTED; + } +} + int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) { switch (which) { case PR_SPEC_STORE_BYPASS: return ssb_prctl_get(task); + case PR_SPEC_INDIR_BRANCH: + return indir_branch_prctl_get(task); default: return -ENODEV; } @@ -975,6 +1044,8 @@ static char *stibp_state(void) return ", STIBP: disabled"; case SPECTRE_V2_APP2APP_STRICT: return ", STIBP: forced"; + case SPECTRE_V2_APP2APP_PRCTL: + return ""; } return ""; } --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1453,6 +1453,8 @@ static inline bool is_percpu_thread(void #define PFA_SPREAD_SLAB 2 /* Spread some slab caches over cpuset */ #define PFA_SPEC_SSB_DISABLE 3 /* Speculative Store Bypass disabled */ #define PFA_SPEC_SSB_FORCE_DISABLE 4 /* Speculative Store Bypass force disabled*/ +#define PFA_SPEC_INDIR_BRANCH_DISABLE 5 /* Indirect branch speculation restricted */ +#define PFA_SPEC_INDIR_BRANCH_FORCE_DISABLE 6 /* Indirect branch speculation permanentely restricted */ #define TASK_PFA_TEST(name, func) \ static inline bool task_##func(struct task_struct *p) \ @@ -1484,6 +1486,13 @@ TASK_PFA_CLEAR(SPEC_SSB_DISABLE, spec_ss TASK_PFA_TEST(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable) TASK_PFA_SET(SPEC_SSB_FORCE_DISABLE, spec_ssb_force_disable) +TASK_PFA_TEST(SPEC_INDIR_BRANCH_DISABLE, spec_indir_branch_disable) +TASK_PFA_SET(SPEC_INDIR_BRANCH_DISABLE, spec_indir_branch_disable) +TASK_PFA_CLEAR(SPEC_INDIR_BRANCH_DISABLE, spec_indir_branch_disable) + +TASK_PFA_TEST(SPEC_INDIR_BRANCH_FORCE_DISABLE, spec_indir_branch_force_disable) +TASK_PFA_SET(SPEC_INDIR_BRANCH_FORCE_DISABLE, spec_indir_branch_force_disable) + static inline void current_restore_flags(unsigned long orig_flags, unsigned long flags) { --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -212,6 +212,7 @@ struct prctl_mm_map { #define PR_SET_SPECULATION_CTRL 53 /* Speculation control variants */ # define PR_SPEC_STORE_BYPASS 0 +# define PR_SPEC_INDIR_BRANCH 1 /* Return and control values for PR_SET/GET_SPECULATION_CTRL */ # define PR_SPEC_NOT_AFFECTED 0 # define PR_SPEC_PRCTL (1UL << 0) --- a/tools/include/uapi/linux/prctl.h +++ b/tools/include/uapi/linux/prctl.h @@ -212,6 +212,7 @@ struct prctl_mm_map { #define PR_SET_SPECULATION_CTRL 53 /* Speculation control variants */ # define PR_SPEC_STORE_BYPASS 0 +# define PR_SPEC_INDIR_BRANCH 1 /* Return and control values for PR_SET/GET_SPECULATION_CTRL */ # define PR_SPEC_NOT_AFFECTED 0 # define PR_SPEC_PRCTL (1UL << 0)