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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 1015AC04AAC for ; Thu, 23 May 2019 08:54:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D01252075E for ; Thu, 23 May 2019 08:54:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730171AbfEWIyR (ORCPT ); Thu, 23 May 2019 04:54:17 -0400 Received: from mga11.intel.com ([192.55.52.93]:14584 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725814AbfEWIyR (ORCPT ); Thu, 23 May 2019 04:54:17 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 May 2019 01:54:16 -0700 X-ExtLoop1: 1 Received: from yhuang-dev.sh.intel.com ([10.239.159.29]) by orsmga002.jf.intel.com with ESMTP; 23 May 2019 01:54:12 -0700 From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Michal Hocko , Hugh Dickins , "Paul E . McKenney" , Minchan Kim , Johannes Weiner , Tim Chen , Mel Gorman , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Andrea Arcangeli , Yang Shi , David Rientjes , Rik van Riel , Jan Kara , Dave Jiang , Daniel Jordan , Andrea Parri Subject: [PATCH -mm] mm: fix race between swapoff and mincore Date: Thu, 23 May 2019 16:53:47 +0800 Message-Id: <20190523085347.14498-1-ying.huang@intel.com> X-Mailer: git-send-email 2.20.1 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: Huang Ying Via commit 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks") on, after swapoff, the address_space associated with the swap device will be freed. So swap_address_space() users which touch the address_space need some kind of mechanism to prevent the address_space from being freed during accessing. When mincore process unmapped range for swapped shmem pages, it doesn't hold the lock to prevent swap device from being swapoff. So the following race is possible, CPU1 CPU2 do_mincore() swapoff() walk_page_range() mincore_unmapped_range() __mincore_unmapped_range mincore_page as = swap_address_space() ... exit_swap_address_space() ... kvfree(spaces) find_get_page(as) The address space may be accessed after being freed. To fix the race, get_swap_device()/put_swap_device() is used to enclose find_get_page() to check whether the swap entry is valid and prevent the swap device from being swapoff during accessing. Fixes: 4b3ef9daa4fc ("mm/swap: split swap cache into 64MB trunks") Signed-off-by: "Huang, Ying" Reviewed-by: Andrew Morton Acked-by: Michal Hocko Cc: Hugh Dickins Cc: Paul E. McKenney Cc: Minchan Kim Cc: Johannes Weiner Cc: Tim Chen Cc: Mel Gorman Cc: Jérôme Glisse Cc: Andrea Arcangeli Cc: Yang Shi Cc: David Rientjes Cc: Rik van Riel Cc: Jan Kara Cc: Dave Jiang Cc: Daniel Jordan Cc: Andrea Parri --- mm/mincore.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/mincore.c b/mm/mincore.c index c3f058bd0faf..4fe91d497436 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -68,8 +68,16 @@ static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) */ if (xa_is_value(page)) { swp_entry_t swp = radix_to_swp_entry(page); - page = find_get_page(swap_address_space(swp), - swp_offset(swp)); + struct swap_info_struct *si; + + /* Prevent swap device to being swapoff under us */ + si = get_swap_device(swp); + if (si) { + page = find_get_page(swap_address_space(swp), + swp_offset(swp)); + put_swap_device(si); + } else + page = NULL; } } else page = find_get_page(mapping, pgoff); -- 2.20.1