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=-13.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 1088DC433E6 for ; Tue, 1 Sep 2020 16:27:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2C8D2098B for ; Tue, 1 Sep 2020 16:27:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598977676; bh=R6W6fnSTZ1QTJue7Um2IqVtxneaYMRCI+li5qnZYrcw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=mCHx7MKVRynsbUx9TytS5R/+B654ZUVQiAhApHXHEtX7fyEvKYgUj+R9FzceLqZiI 32rjNpshbhyNGYjeP59riw2H9XyQqEQ81VwkFOnTDGJK3nXWbwKDW836vKW21t6Ilb KFtSqRO3oQeQSjKIyHDJu2BZs+Zgvi9xXvxDM3rg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730860AbgIAPcE (ORCPT ); Tue, 1 Sep 2020 11:32:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:59774 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730573AbgIAP3z (ORCPT ); Tue, 1 Sep 2020 11:29:55 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 55FAB206C0; Tue, 1 Sep 2020 15:29:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598974194; bh=R6W6fnSTZ1QTJue7Um2IqVtxneaYMRCI+li5qnZYrcw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IQpTy3SRivpUmlq9Sh5g8djRHfKSv1C1F9lvIkUehyv0xMc7BKW3FATMmJhGOm/km Gldm2wWt1vak3CUqksb1fpjg7sh93SVqPHwb3Z0kcIGUCUQzDGNIPjFVMgh5L446J0 k9ZnV4kWyeyNOufJU4TZx/jwHr6bSG+3TGNYFUds= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , "Peter Zijlstra (Intel)" , Andrew Morton , Nicholas Piggin , Jens Axboe , Kees Cook , Jann Horn , Will Deacon , Christoph Hellwig , Mathieu Desnoyers , Linus Torvalds , Sasha Levin Subject: [PATCH 5.4 081/214] mm: fix kthread_use_mm() vs TLB invalidate Date: Tue, 1 Sep 2020 17:09:21 +0200 Message-Id: <20200901150956.873446830@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200901150952.963606936@linuxfoundation.org> References: <20200901150952.963606936@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra [ Upstream commit 38cf307c1f2011d413750c5acb725456f47d9172 ] For SMP systems using IPI based TLB invalidation, looking at current->active_mm is entirely reasonable. This then presents the following race condition: CPU0 CPU1 flush_tlb_mm(mm) use_mm(mm) tsk->active_mm = mm; if (tsk->active_mm == mm) // flush TLBs switch_mm(old_mm,mm,tsk); Where it is possible the IPI flushed the TLBs for @old_mm, not @mm, because the IPI lands before we actually switched. Avoid this by disabling IRQs across changing ->active_mm and switch_mm(). Of the (SMP) architectures that have IPI based TLB invalidate: Alpha - checks active_mm ARC - ASID specific IA64 - checks active_mm MIPS - ASID specific flush OpenRISC - shoots down world PARISC - shoots down world SH - ASID specific SPARC - ASID specific x86 - N/A xtensa - checks active_mm So at the very least Alpha, IA64 and Xtensa are suspect. On top of this, for scheduler consistency we need at least preemption disabled across changing tsk->mm and doing switch_mm(), which is currently provided by task_lock(), but that's not sufficient for PREEMPT_RT. [akpm@linux-foundation.org: add comment] Reported-by: Andy Lutomirski Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Andrew Morton Cc: Nicholas Piggin Cc: Jens Axboe Cc: Kees Cook Cc: Jann Horn Cc: Will Deacon Cc: Christoph Hellwig Cc: Mathieu Desnoyers Cc: Link: http://lkml.kernel.org/r/20200721154106.GE10769@hirez.programming.kicks-ass.net Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/mmu_context.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/mmu_context.c b/mm/mmu_context.c index 3e612ae748e96..a1da47e027479 100644 --- a/mm/mmu_context.c +++ b/mm/mmu_context.c @@ -25,13 +25,16 @@ void use_mm(struct mm_struct *mm) struct task_struct *tsk = current; task_lock(tsk); + /* Hold off tlb flush IPIs while switching mm's */ + local_irq_disable(); active_mm = tsk->active_mm; if (active_mm != mm) { mmgrab(mm); tsk->active_mm = mm; } tsk->mm = mm; - switch_mm(active_mm, mm, tsk); + switch_mm_irqs_off(active_mm, mm, tsk); + local_irq_enable(); task_unlock(tsk); #ifdef finish_arch_post_lock_switch finish_arch_post_lock_switch(); @@ -56,9 +59,11 @@ void unuse_mm(struct mm_struct *mm) task_lock(tsk); sync_mm_rss(mm); + local_irq_disable(); tsk->mm = NULL; /* active_mm is still 'mm' */ enter_lazy_tlb(mm, tsk); + local_irq_enable(); task_unlock(tsk); } EXPORT_SYMBOL_GPL(unuse_mm); -- 2.25.1