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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 3F462C48BD1 for ; Wed, 9 Jun 2021 12:20:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 23A5A61287 for ; Wed, 9 Jun 2021 12:20:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239794AbhFIMWw (ORCPT ); Wed, 9 Jun 2021 08:22:52 -0400 Received: from foss.arm.com ([217.140.110.172]:58798 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235788AbhFIMWj (ORCPT ); Wed, 9 Jun 2021 08:22:39 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7B31D150C; Wed, 9 Jun 2021 05:20:44 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 511BE3F73D; Wed, 9 Jun 2021 05:20:41 -0700 (PDT) From: Mark Rutland To: linux-kernel@vger.kernel.org Cc: benh@kernel.crashing.org, boqun.feng@gmail.com, bp@alien8.de, catalin.marinas@arm.com, dvyukov@google.com, elver@google.com, ink@jurassic.park.msu.ru, jonas@southpole.se, juri.lelli@redhat.com, linux@armlinux.org.uk, luto@kernel.org, mark.rutland@arm.com, mattst88@gmail.com, mingo@redhat.com, monstr@monstr.eu, mpe@ellerman.id.au, paulmck@kernel.org, paulus@samba.org, peterz@infradead.org, rth@twiddle.net, shorne@gmail.com, stefan.kristiansson@saunalahti.fi, tglx@linutronix.de, vincent.guittot@linaro.org, will@kernel.org Subject: [RFC PATCH 10/10] x86: snapshot thread flags Date: Wed, 9 Jun 2021 13:20:01 +0100 Message-Id: <20210609122001.18277-11-mark.rutland@arm.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20210609122001.18277-1-mark.rutland@arm.com> References: <20210609122001.18277-1-mark.rutland@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some thread flags can be set remotely, and so even when IRQs are disabled, the flags can change under our feet. Generally this is unlikely to cause a problem in practice, but it is somewhat unsound, and KCSAN will legitimately warn that there is a data race. To avoid such issues, we should snapshot the flags prior to using them. Let's use the new helpers to do so on x86. Signed-off-by: Mark Rutland Cc: Borislav Petkov Cc: Ingo Molnar Cc: Thomas Gleixner --- arch/x86/kernel/process.c | 8 ++++---- arch/x86/kernel/process.h | 6 +++--- arch/x86/mm/tlb.c | 2 +- 3 files changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 5e1f38179f49..d1c4a93c6e26 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -332,7 +332,7 @@ void arch_setup_new_exec(void) clear_thread_flag(TIF_SSBD); task_clear_spec_ssb_disable(current); task_clear_spec_ssb_noexec(current); - speculation_ctrl_update(task_thread_info(current)->flags); + speculation_ctrl_update(read_thread_flags()); } } @@ -584,7 +584,7 @@ static unsigned long speculation_ctrl_update_tif(struct task_struct *tsk) clear_tsk_thread_flag(tsk, TIF_SPEC_IB); } /* Return the updated threadinfo flags*/ - return task_thread_info(tsk)->flags; + return read_task_thread_flags(tsk); } void speculation_ctrl_update(unsigned long tif) @@ -620,8 +620,8 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p) { unsigned long tifp, tifn; - tifn = READ_ONCE(task_thread_info(next_p)->flags); - tifp = READ_ONCE(task_thread_info(prev_p)->flags); + tifn = read_task_thread_flags(next_p); + tifp = read_task_thread_flags(prev_p); switch_to_bitmap(tifp); diff --git a/arch/x86/kernel/process.h b/arch/x86/kernel/process.h index 1d0797b2338a..0b1be8685b49 100644 --- a/arch/x86/kernel/process.h +++ b/arch/x86/kernel/process.h @@ -13,9 +13,9 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p); static inline void switch_to_extra(struct task_struct *prev, struct task_struct *next) { - unsigned long next_tif = task_thread_info(next)->flags; - unsigned long prev_tif = task_thread_info(prev)->flags; - + unsigned long next_tif = read_task_thread_flags(next); + unsigned long prev_tif = read_task_thread_flags(prev); + if (IS_ENABLED(CONFIG_SMP)) { /* * Avoid __switch_to_xtra() invocation when conditional diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 78804680e923..fcc5e22050d4 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -318,7 +318,7 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next, static unsigned long mm_mangle_tif_spec_ib(struct task_struct *next) { - unsigned long next_tif = task_thread_info(next)->flags; + unsigned long next_tif = read_task_thread_flags(next); unsigned long ibpb = (next_tif >> TIF_SPEC_IB) & LAST_USER_MM_IBPB; return (unsigned long)next->mm | ibpb; -- 2.11.0