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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 B8603C282C4 for ; Mon, 4 Feb 2019 10:55:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8835B20823 for ; Mon, 4 Feb 2019 10:55:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549277702; bh=3TpVy4DLGtVK5ArIyIykWdsJc/ujxYnMbBgKc1yfFjY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Lg77a4/HgiPcWV0zCQga22ieWBoLfvtF3CdOpGmYrhRh8QexfXq6Aw6qgVlwzy4HO j+ajnD3bQecuWaOzFM49S7dsNpLMcChTsmR+NS6qhaR+9occI+RFMUypQNn1azW0gU IWMmuVyXdMmGtXSOQkHBDyhX+tAHBGeJfuBEp/XE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732979AbfBDKzA (ORCPT ); Mon, 4 Feb 2019 05:55:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:51922 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732260AbfBDKyK (ORCPT ); Mon, 4 Feb 2019 05:54:10 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 62F0C2176F; Mon, 4 Feb 2019 10:54:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549277648; bh=3TpVy4DLGtVK5ArIyIykWdsJc/ujxYnMbBgKc1yfFjY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=liH6xpkFE9SmArn/0KnfWE6fz4qfjJE5NSmDvKl93u9A38tU57dyFhW9lU+6z6J+R 8CDKCjVCkvthaD96RN0qvh/4kDcTKeCBfnb2T9s0w0vq9axDijz2GKjal4gfFTG/LX CZ0YAxwzrjWBLP0eSUe0Yp6+OrJqnP5TFJ0ZnUIc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Hildenbrand , Vratislav Bendel , Michal Hocko , Rafael Aquini , Mel Gorman , "Kirill A. Shutemov" , Naoya Horiguchi , Jan Kara , Andrea Arcangeli , Dominik Brodowski , Matthew Wilcox , Konstantin Khlebnikov , Minchan Kim , Andrew Morton , Linus Torvalds Subject: [PATCH 4.20 74/80] mm: migrate: dont rely on __PageMovable() of newpage after unlocking it Date: Mon, 4 Feb 2019 11:37:34 +0100 Message-Id: <20190204103630.248305575@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190204103620.287366543@linuxfoundation.org> References: <20190204103620.287366543@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore 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 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ From: David Hildenbrand commit e0a352fabce61f730341d119fbedf71ffdb8663f upstream. We had a race in the old balloon compaction code before b1123ea6d3b3 ("mm: balloon: use general non-lru movable page feature") refactored it that became visible after backporting 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 b1123ea6d3b3 ("mm: balloon: use general non-lru movable page feature"). 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 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). Link: http://lkml.kernel.org/r/20190129233217.10747-1-david@redhat.com Fixes: d6d86c0a7f8d ("mm/balloon_compaction: redesign ballooned pages management") Signed-off-by: David Hildenbrand Reported-by: Vratislav Bendel Acked-by: Michal Hocko Acked-by: Rafael Aquini 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: [3.12 - 4.7] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/migrate.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1108,10 +1108,13 @@ out: * If migration is successful, decrease refcount of the newpage * which will not free the page because new page owner increased * refcounter. As well, if it is LRU page, add the page to LRU - * list in here. + * list in here. 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 (rc == MIGRATEPAGE_SUCCESS) { - if (unlikely(__PageMovable(newpage))) + if (unlikely(!is_lru)) put_page(newpage); else putback_lru_page(newpage);