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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 52230C19F29 for ; Wed, 27 Jul 2022 19:25:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DD067940026; Wed, 27 Jul 2022 15:25:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D7FAD940012; Wed, 27 Jul 2022 15:25:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C216D940026; Wed, 27 Jul 2022 15:25:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id B3457940012 for ; Wed, 27 Jul 2022 15:25:27 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 5DA13140C2A for ; Wed, 27 Jul 2022 19:25:26 +0000 (UTC) X-FDA: 79733858652.24.C6E7EDD Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf30.hostedemail.com (Postfix) with ESMTP id 326B480026 for ; Wed, 27 Jul 2022 19:25:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=8PMF9RAfUsWsnizFrlCJPvao6aXNiFYw1zm8tW5odss=; b=UTld7/z9lGtIVo/RpBaSKOEH8v UrD4YlPiJURock7BXSSlf1jzkbcbdGDlsQo4AyRaJMgLpW6dGSkIBjqsPwBYDCX0Jg36XSWyUTnXY c3SpqEKj0514G8SqlIZ5BSczg8Rd2SFYdXgyIWdnLQ8lHIDSMFaIw/CKuiqoxIpWX8PIeq+RTSW/z qi0bUlwtjysoMUYLMPHCIxbq+JRykUdzQFC08EDFKdMoRYhgcDGBm4AqR715MlPZr84szRGq4nLIB OLolH7N0QQzZg9AcV4rJEM1saEU5fDy20jEBISvTwquU5zR45qN6WFTcerdrDiP/HE0W66HM3BYvz SyX38R9A==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1oGme6-003AhV-H5; Wed, 27 Jul 2022 19:24:38 +0000 Date: Wed, 27 Jul 2022 20:24:38 +0100 From: Matthew Wilcox To: Zack Rusin Cc: dri-devel@lists.freedesktop.org, krastevm@vmware.com, mombasawalam@vmware.com, banackm@vmware.com, David Hildenbrand , Vlastimil Babka , Andrea Arcangeli , Christoph Hellwig , David Rientjes , Don Dutile , Hugh Dickins , Jan Kara , Jann Horn , Jason Gunthorpe , John Hubbard , Khalid Aziz , "Kirill A. Shutemov" , Liang Zhang , Michal Hocko , Mike Kravetz , Mike Rapoport , Nadav Amit , Oded Gabbay , Oleg Nesterov , Pedro Demarchi Gomes , Peter Xu , Rik van Riel , Roman Gushchin , Shakeel Butt , Yang Shi , Andrew Morton , Muchun Song , Minchan Kim , David Howells , Miaohe Lin , NeilBrown , Suren Baghdasaryan , Hongchen Zhang , linux-mm@kvack.org Subject: Re: [PATCH] mm: Fix a null ptr deref with CONFIG_DEBUG_VM enabled in wp_page_reuse Message-ID: References: <20220727191407.1768600-1-zack@kde.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220727191407.1768600-1-zack@kde.org> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1658949925; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=8PMF9RAfUsWsnizFrlCJPvao6aXNiFYw1zm8tW5odss=; b=O5OCJWoWb7tkVjZpzff7bgoM09UhftzCNx6yQCVOd444cUpGNGtJHsWtTb+ruch9avREl1 754gmTGEA7hni0jDZSC1G3BHhHGOkAI24Pw+DFeQk1kBdDHyfqlpdI4EeSENQHZ/FzmM84 WtiSsfHjKwjZJj7B/+r8VlTwsMfxO4U= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="UTld7/z9"; spf=none (imf30.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1658949925; a=rsa-sha256; cv=none; b=Wu5Z7g0hVJruZchr20220oCOM/Uf5WdYsXv8A3OINoK2biXt7zi++SYq2icBfAzveKvDLC FDu21liCM//Az8ryxmxhsZ7OkiU1HdoR27ZQPL23CNUBJe2D9QoqikVN2vgkSuodwAttzn iibszrNSK02IQWybiEmoPcj9JnEGO1o= X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 326B480026 X-Rspam-User: Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b="UTld7/z9"; spf=none (imf30.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-Stat-Signature: 1krq9mem716m7hstujpdug3tgu69p3tc X-HE-Tag: 1658949923-889380 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jul 27, 2022 at 03:14:07PM -0400, Zack Rusin wrote: > From: Zack Rusin > > Write page faults on last references might not have a valid page anymore. > wp_page_reuse has always dealt with that scenario by making > sure the page isn't null (or the reference was shared) before doing > anything with it. Recently added checks in VM_BUG_ON (enabled by the > CONFIG_DEBUG_VM option) use PageAnon helpers which assume the passed > page is never null, before making sure there is a valid page to work > with. > > Move the VM_BUG_ON, which unconditionally uses the page, after the > code that checks that we have a valid one. Message-ID: