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 7513AC433B4 for ; Thu, 8 Apr 2021 13:09:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F97F6113C for ; Thu, 8 Apr 2021 13:09:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231622AbhDHNJc (ORCPT ); Thu, 8 Apr 2021 09:09:32 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:16414 "EHLO szxga06-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230412AbhDHNJa (ORCPT ); Thu, 8 Apr 2021 09:09:30 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4FGM4L1CWSzkjgG; Thu, 8 Apr 2021 21:07:30 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.498.0; Thu, 8 Apr 2021 21:09:10 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , Subject: [PATCH 4/5] mm/swap_state: fix potential faulted in race in swap_ra_info() Date: Thu, 8 Apr 2021 09:08:19 -0400 Message-ID: <20210408130820.48233-5-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20210408130820.48233-1-linmiaohe@huawei.com> References: <20210408130820.48233-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.104.175] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While we released the pte lock, somebody else might faulted in this pte. So we should check whether it's swap pte first to guard against such race or swp_type would be unexpected. And we can also avoid some unnecessary readahead cpu cycles possibly. Fixes: ec560175c0b6 ("mm, swap: VMA based swap readahead") Signed-off-by: Miaohe Lin --- mm/swap_state.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 709c260d644a..3bf0d0c297bc 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -724,10 +724,10 @@ static void swap_ra_info(struct vm_fault *vmf, { struct vm_area_struct *vma = vmf->vma; unsigned long ra_val; - swp_entry_t entry; + swp_entry_t swap_entry; unsigned long faddr, pfn, fpfn; unsigned long start, end; - pte_t *pte, *orig_pte; + pte_t *pte, *orig_pte, entry; unsigned int max_win, hits, prev_win, win, left; #ifndef CONFIG_64BIT pte_t *tpte; @@ -742,8 +742,13 @@ static void swap_ra_info(struct vm_fault *vmf, faddr = vmf->address; orig_pte = pte = pte_offset_map(vmf->pmd, faddr); - entry = pte_to_swp_entry(*pte); - if ((unlikely(non_swap_entry(entry)))) { + entry = *pte; + if (unlikely(!is_swap_pte(entry))) { + pte_unmap(orig_pte); + return; + } + swap_entry = pte_to_swp_entry(entry); + if ((unlikely(non_swap_entry(swap_entry)))) { pte_unmap(orig_pte); return; } -- 2.19.1