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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 23B00C004D5 for ; Sat, 29 Sep 2018 21:49:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E56432087A for ; Sat, 29 Sep 2018 21:49:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E56432087A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk 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 S1729177AbeI3ETs (ORCPT ); Sun, 30 Sep 2018 00:19:48 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:52144 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728890AbeI3ESh (ORCPT ); Sun, 30 Sep 2018 00:18:37 -0400 Received: from [2a02:8011:400e:2:cbab:f00:c93f:614] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1g6N6H-0000H1-I3; Sat, 29 Sep 2018 22:48:33 +0100 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1g6N5v-0006qh-R9; Sat, 29 Sep 2018 22:48:11 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Thomas Gleixner" Date: Sat, 29 Sep 2018 22:43:07 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 023/131] seccomp: Move speculation migitation control to arch code In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:cbab:f00:c93f:614 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.59-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit 8bf37d8c067bb7eb8e7c381bdadf9bd89182b6bc upstream. The migitation control is simpler to implement in architecture code as it avoids the extra function call to check the mode. Aside of that having an explicit seccomp enabled mode in the architecture mitigations would require even more workarounds. Move it into architecture code and provide a weak function in the seccomp code. Remove the 'which' argument as this allows the architecture to decide which mitigations are relevant for seccomp. Signed-off-by: Thomas Gleixner [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- arch/x86/kernel/cpu/bugs.c | 29 ++++++++++++++++++----------- include/linux/nospec.h | 2 ++ kernel/seccomp.c | 15 ++------------- 3 files changed, 22 insertions(+), 24 deletions(-) --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -606,6 +606,24 @@ static int ssb_prctl_set(struct task_str 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); + default: + return -ENODEV; + } +} + +#ifdef CONFIG_SECCOMP +void arch_seccomp_spec_mitigate(struct task_struct *task) +{ + ssb_prctl_set(task, PR_SPEC_FORCE_DISABLE); +} +#endif + static int ssb_prctl_get(struct task_struct *task) { switch (ssb_mode) { @@ -624,17 +642,6 @@ static int ssb_prctl_get(struct task_str } } -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); - default: - return -ENODEV; - } -} - int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) { switch (which) { --- a/include/linux/nospec.h +++ b/include/linux/nospec.h @@ -62,5 +62,7 @@ static inline unsigned long array_index_ int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which); int arch_prctl_spec_ctrl_set(struct task_struct *task, unsigned long which, unsigned long ctrl); +/* Speculation control for seccomp enforced mitigation */ +void arch_seccomp_spec_mitigate(struct task_struct *task); #endif /* _LINUX_NOSPEC_H */ --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -207,18 +207,7 @@ static inline bool seccomp_may_assign_mo return true; } -/* - * If a given speculation mitigation is opt-in (prctl()-controlled), - * select it, by disabling speculation (enabling mitigation). - */ -static inline void spec_mitigate(struct task_struct *task, - unsigned long which) -{ - int state = arch_prctl_spec_ctrl_get(task, which); - - if (state > 0 && (state & PR_SPEC_PRCTL)) - arch_prctl_spec_ctrl_set(task, which, PR_SPEC_FORCE_DISABLE); -} +void __weak arch_seccomp_spec_mitigate(struct task_struct *task) { } static inline void seccomp_assign_mode(unsigned long seccomp_mode, unsigned long flags) @@ -226,7 +215,7 @@ static inline void seccomp_assign_mode(u current->seccomp.mode = seccomp_mode; /* Assume default seccomp processes want spec flaw mitigation. */ if ((flags & SECCOMP_FILTER_FLAG_SPEC_ALLOW) == 0) - spec_mitigate(current, PR_SPEC_STORE_BYPASS); + arch_seccomp_spec_mitigate(current); set_tsk_thread_flag(current, TIF_SECCOMP); }