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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 CA322C282DA for ; Fri, 1 Feb 2019 13:44:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A5B052082C for ; Fri, 1 Feb 2019 13:44:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730164AbfBANn7 (ORCPT ); Fri, 1 Feb 2019 08:43:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44522 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726737AbfBANn7 (ORCPT ); Fri, 1 Feb 2019 08:43:59 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A4EE081F11; Fri, 1 Feb 2019 13:43:58 +0000 (UTC) Received: from t460s.redhat.com (unknown [10.36.118.43]) by smtp.corp.redhat.com (Postfix) with ESMTP id A963C1974A; Fri, 1 Feb 2019 13:43:48 +0000 (UTC) From: David Hildenbrand To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, David Hildenbrand , Andrew Morton , Mel Gorman , "Kirill A. Shutemov" , Michal Hocko , Naoya Horiguchi , Jan Kara , Andrea Arcangeli , Dominik Brodowski , Matthew Wilcox , Vratislav Bendel , Rafael Aquini , Konstantin Khlebnikov , Minchan Kim , Sasha Levin , stable@vger.kernel.org Subject: [PATCH v2 for-4.4-stable] mm: migrate: don't rely on __PageMovable() of newpage after unlocking it Date: Fri, 1 Feb 2019 14:43:47 +0100 Message-Id: <20190201134347.11166-1-david@redhat.com> In-Reply-To: <20190131020448.072FE218AF@mail.kernel.org> References: <20190131020448.072FE218AF@mail.kernel.org> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Fri, 01 Feb 2019 13:43:59 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is the backport for 4.4-stable. We had a race in the old balloon compaction code before commit b1123ea6d3b3 ("mm: balloon: use general non-lru movable page feature") refactored it that became visible after backporting commit 195a8c43e93d ("virtio-balloon: deflate via a page list") without the refactoring. The bug existed from commit d6d86c0a7f8d ("mm/balloon_compaction: redesign ballooned pages management") till commit b1123ea6d3b3 ("mm: balloon: use general non-lru movable page feature"). commit d6d86c0a7f8d ("mm/balloon_compaction: redesign ballooned pages management") was backported to 3.12, so the broken kernels are stable kernels [3.12 - 4.7]. There was a subtle race between dropping the page lock of the newpage in __unmap_and_move() and checking for __is_movable_balloon_page(newpage). Just after dropping this page lock, virtio-balloon could go ahead and deflate the newpage, effectively dequeueing it and clearing PageBalloon, in turn making __is_movable_balloon_page(newpage) fail. This resulted in dropping the reference of the newpage via putback_lru_page(newpage) instead of put_page(newpage), leading to page->lru getting modified and a !LRU page ending up in the LRU lists. With commit 195a8c43e93d ("virtio-balloon: deflate via a page list") backported, one would suddenly get corrupted lists in release_pages_balloon(): - WARNING: CPU: 13 PID: 6586 at lib/list_debug.c:59 __list_del_entry+0xa1/0xd0 - list_del corruption. prev->next should be ffffe253961090a0, but was dead000000000100 Nowadays this race is no longer possible, but it is hidden behind very ugly handling of __ClearPageMovable() and __PageMovable(). __ClearPageMovable() will not make __PageMovable() fail, only PageMovable(). So the new check (__PageMovable(newpage)) will still hold even after newpage was dequeued by virtio-balloon. If anybody would ever change that special handling, the BUG would be introduced again. So instead, make it explicit and use the information of the original isolated page before migration. This patch can be backported fairly easy to stable kernels (in contrast to the refactoring). Cc: Andrew Morton Cc: Mel Gorman Cc: "Kirill A. Shutemov" Cc: Michal Hocko Cc: Naoya Horiguchi Cc: Jan Kara Cc: Andrea Arcangeli Cc: Dominik Brodowski Cc: Matthew Wilcox Cc: Vratislav Bendel Cc: Rafael Aquini Cc: Konstantin Khlebnikov Cc: Minchan Kim Cc: Sasha Levin Cc: stable@vger.kernel.org # 3.12 - 4.7 Fixes: d6d86c0a7f8d ("mm/balloon_compaction: redesign ballooned pages management") Reported-by: Vratislav Bendel Acked-by: Michal Hocko Acked-by: Rafael Aquini Signed-off-by: David Hildenbrand --- mm/migrate.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/migrate.c b/mm/migrate.c index afedcfab60e2..3304c98f9a78 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -936,6 +936,7 @@ static ICE_noinline int unmap_and_move(new_page_t get_new_page, int rc = MIGRATEPAGE_SUCCESS; int *result = NULL; struct page *newpage; + bool is_lru = !isolated_balloon_page(page); newpage = get_new_page(page, private, &result); if (!newpage) @@ -984,10 +985,14 @@ out: * If migration was not successful and there's a freeing callback, use * it. Otherwise, putback_lru_page() will drop the reference grabbed * during isolation. + * + * Use the old state of the isolated source page to determine if we + * migrated a LRU page. newpage was already unlocked and possibly + * modified by its owner - don't rely on the page state. */ if (put_new_page) put_new_page(newpage, private); - else if (unlikely(__is_movable_balloon_page(newpage))) { + else if (unlikely(!is_lru)) { /* drop our reference, page already in the balloon */ put_page(newpage); } else -- 2.17.2