From patchwork Tue Dec 12 11:43:50 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 10106743 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id AB9776032B for ; Tue, 12 Dec 2017 11:44:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9540F29B7A for ; Tue, 12 Dec 2017 11:44:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 89C8229B89; Tue, 12 Dec 2017 11:44:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id E99C229B7A for ; Tue, 12 Dec 2017 11:44:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:Message-Id:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Owner; bh=ZZi32uQ6OgT8gj2jZ+FN7llnOjbjvKYInwGHG4OJ6LE=; b=Rlt KLfknv127c9wEFbKwQD9pKrwpBv3G2PjJfEi/KpenjKrlnD4S9W5DdYAp13U4Kq5TBf4T/lJhk3FQ 2pV3qTFMNFHorYW3wKISUvITqgTPFsY0Be23/r7WVyUS6t6S8D7TcOTCxi+7Q55Gf9vjvxUOavmCl bLwRjHifHMWMpM2wM5AXL87E9/uiJvXOHNWk5YmtSPmP6NtgorKsqW2kfVLCTSgRkfm3fo6HP7G0l P/DN0xNt+XzgSvL/cDhv++QKFp9N1nW+RBdkwQOXZewtfhbJuDT3iPsuumC/gvx6Q+FJcr0pJPopj XUIBSV8sCED2yWhGwOPIesGhJmUB+Jw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eOiyn-0005Vj-MT; Tue, 12 Dec 2017 11:44:09 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eOiyk-0005Tb-1E for linux-arm-kernel@lists.infradead.org; Tue, 12 Dec 2017 11:44:07 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 38F8E1529; Tue, 12 Dec 2017 03:43:44 -0800 (PST) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 0A4FF3F24A; Tue, 12 Dec 2017 03:43:44 -0800 (PST) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 1EB401AE13AF; Tue, 12 Dec 2017 11:43:52 +0000 (GMT) From: Will Deacon To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] arm64: mm: Fix false positives in set_pte_at access/dirty race detection Date: Tue, 12 Dec 2017 11:43:50 +0000 Message-Id: <1513079030-8557-1-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 2.1.4 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171212_034406_118866_0C04CE87 X-CRM114-Status: UNSURE ( 9.68 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yisheng Xie , catalin.marinas@arm.com, Will Deacon MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Jiankang reports that our race detection in set_pte_at is firing when copying the page tables in dup_mmap as a result of a fork(). In this situation, the page table isn't actually live and so there is no way that we can race with a concurrent update from the hardware page table walker. This patch reworks the race detection so that we require either the mm to match the current active_mm (i.e. currently installed in our TTBR0) or the mm_users count to be greater than 1, implying that the page table could be live in another CPU. The mm_users check might still be racy, but we'll avoid false positives and it's not realistic to validate that all the necessary locks are held as part of this assertion. Cc: Yisheng Xie Reported-by: Jiankang Chen Tested-by: Jiankang Chen Signed-off-by: Will Deacon --- arch/arm64/include/asm/pgtable.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 3ff03a755c32..bdcc7f1c9d06 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -42,6 +42,8 @@ #include #include #include +#include +#include extern void __pte_error(const char *file, int line, unsigned long val); extern void __pmd_error(const char *file, int line, unsigned long val); @@ -215,9 +217,6 @@ static inline void set_pte(pte_t *ptep, pte_t pte) } } -struct mm_struct; -struct vm_area_struct; - extern void __sync_icache_dcache(pte_t pteval, unsigned long addr); /* @@ -246,7 +245,8 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, * hardware updates of the pte (ptep_set_access_flags safely changes * valid ptes without going through an invalid entry). */ - if (pte_valid(*ptep) && pte_valid(pte)) { + if (IS_ENABLED(CONFIG_DEBUG_VM) && pte_valid(*ptep) && pte_valid(pte) && + (mm == current->active_mm || atomic_read(&mm->mm_users) > 1)) { VM_WARN_ONCE(!pte_young(pte), "%s: racy access flag clearing: 0x%016llx -> 0x%016llx", __func__, pte_val(*ptep), pte_val(pte));