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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_RED,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 65E0FC433ED for ; Thu, 20 May 2021 11:22:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 432466135A for ; Thu, 20 May 2021 11:22:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240909AbhETLXq (ORCPT ); Thu, 20 May 2021 07:23:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:59276 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238055AbhETLDF (ORCPT ); Thu, 20 May 2021 07:03:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8FF9161926; Thu, 20 May 2021 10:04:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621505058; bh=rKn9MHJ5/JUR77Gzufu0d8whZCTWHBYin00CJMH6BIs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cUGCxf8eMujpsvibb88wuUhhCVdYzUm15XMcYY+Vc+5Qi/hhdMenIC6oMT6gLUqVv x8iyW6z5eOuIXgMUOzJtqestus2/Uc8i/QQEPNmWrXgEdKRE2FUI4R0GPgnJMmBani hG596ODTZ3sV606rElu9ly1qxg0/Q16RmkNUT5EI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Miaohe Lin , Hugh Dickins , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 4.9 203/240] ksm: fix potential missing rmap_item for stable_node Date: Thu, 20 May 2021 11:23:15 +0200 Message-Id: <20210520092115.472450276@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092108.587553970@linuxfoundation.org> References: <20210520092108.587553970@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Miaohe Lin [ Upstream commit c89a384e2551c692a9fe60d093fd7080f50afc51 ] When removing rmap_item from stable tree, STABLE_FLAG of rmap_item is cleared with head reserved. So the following scenario might happen: For ksm page with rmap_item1: cmp_and_merge_page stable_node->head = &migrate_nodes; remove_rmap_item_from_tree, but head still equal to stable_node; try_to_merge_with_ksm_page failed; return; For the same ksm page with rmap_item2, stable node migration succeed this time. The stable_node->head does not equal to migrate_nodes now. For ksm page with rmap_item1 again: cmp_and_merge_page stable_node->head != &migrate_nodes && rmap_item->head == stable_node return; We would miss the rmap_item for stable_node and might result in failed rmap_walk_ksm(). Fix this by set rmap_item->head to NULL when rmap_item is removed from stable tree. Link: https://lkml.kernel.org/r/20210330140228.45635-5-linmiaohe@huawei.com Fixes: 4146d2d673e8 ("ksm: make !merge_across_nodes migration safe") Signed-off-by: Miaohe Lin Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/ksm.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/ksm.c b/mm/ksm.c index d6c81a5076a7..27ff68050d85 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -629,6 +629,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item) ksm_pages_shared--; put_anon_vma(rmap_item->anon_vma); + rmap_item->head = NULL; rmap_item->address &= PAGE_MASK; } else if (rmap_item->address & UNSTABLE_FLAG) { -- 2.30.2