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 ADFABC433F5 for ; Mon, 4 Apr 2022 22:54:23 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C82E36B0071; Mon, 4 Apr 2022 18:54:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C0A166B0073; Mon, 4 Apr 2022 18:54:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AAC2E6B0074; Mon, 4 Apr 2022 18:54:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id 944C56B0071 for ; Mon, 4 Apr 2022 18:54:12 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 58763235B3 for ; Mon, 4 Apr 2022 22:54:02 +0000 (UTC) X-FDA: 79320701124.13.AAE1FC3 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf24.hostedemail.com (Postfix) with ESMTP id CD8E8180008 for ; Mon, 4 Apr 2022 22:54:01 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id CB38F616C1; Mon, 4 Apr 2022 22:54:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F070C2BBE4; Mon, 4 Apr 2022 22:54:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1649112840; bh=qdF66H42BPEgvH1SOyYChQ8fvKv8/tr1wPWHNAXLe8s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=lQ+qVXCM3MvVO39DD3EqJUXPA/OLav4OqnGe3qPOZ3ChJerjjcwo6FuJ+X4ge0Jgq xrEs0YtKXLMUQQXuQ4QqX8snp6bGndn/oeEkGZUfUnoI5GJgCK7axYv3pKBr4av/80 vmosjtQCFKTRsnspJ1/2iQ+w1jmWsxFJl0uKEsCY= Date: Mon, 4 Apr 2022 15:53:59 -0700 From: Andrew Morton To: Miaohe Lin Cc: , Subject: Re: [PATCH] mm/swapfile: unuse_pte can map random data if swap read fails Message-Id: <20220404155359.d4867fb8717fe40b5a11647c@linux-foundation.org> In-Reply-To: <20220401072926.45051-1-linmiaohe@huawei.com> References: <20220401072926.45051-1-linmiaohe@huawei.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: m5zgk49rjab7yb3mjhb46sa76c4jc7bj Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=lQ+qVXCM; dmarc=none; spf=pass (imf24.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: CD8E8180008 X-HE-Tag: 1649112841-937018 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 Fri, 1 Apr 2022 15:29:26 +0800 Miaohe Lin wrote: > There is a bug in unuse_pte(): when swap page happens to be unreadable, > page filled with random data is mapped into user address space. The fix > is to check for PageUptodate and fail swapoff in case of error. > > ... > > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1795,6 +1795,10 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, > ret = 0; > goto out; > } > + if (unlikely(!PageUptodate(page))) { > + ret = -EIO; > + goto out; > + } > > dec_mm_counter(vma->vm_mm, MM_SWAPENTS); > inc_mm_counter(vma->vm_mm, MM_ANONPAGES); Failing the swapoff after -EIO seems a bit rude. The user ends up with a permanently mounted swap because a sector was bad? That would be like failing truncate() or close() or umount after -EIO on a regular file. Somewhat. Can we do something better? Such as shooting down the page anyway and permitting the swapoff to proceed? Worst case, just leak the dang page with an apologetic message.