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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A607C433F5 for ; Mon, 25 Apr 2022 08:48:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235607AbiDYIu4 (ORCPT ); Mon, 25 Apr 2022 04:50:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232457AbiDYIut (ORCPT ); Mon, 25 Apr 2022 04:50:49 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C94928BF24 for ; Mon, 25 Apr 2022 01:47:44 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KmzCH37Jrzfb32; Mon, 25 Apr 2022 16:46:51 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 25 Apr 2022 16:47:42 +0800 Subject: Re: [PATCH v3 1/3] mm/swapfile: unuse_pte can map random data if swap read fails To: David Hildenbrand , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= CC: "akpm@linux-foundation.org" , "willy@infradead.org" , "vbabka@suse.cz" , "dhowells@redhat.com" , "neilb@suse.de" , "apopple@nvidia.com" , "surenb@google.com" , "minchan@kernel.org" , "peterx@redhat.com" , "sfr@canb.auug.org.au" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" References: <20220424091105.48374-1-linmiaohe@huawei.com> <20220424091105.48374-2-linmiaohe@huawei.com> <20220425010804.GA3746096@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: <3ab987be-614a-4757-4124-26bb09d3f160@huawei.com> Date: Mon, 25 Apr 2022 16:47:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/4/25 15:45, David Hildenbrand wrote: > On 25.04.22 03:08, HORIGUCHI NAOYA(堀口 直也) wrote: >> On Sun, Apr 24, 2022 at 05:11:03PM +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. In case >>> of error, a special swap entry indicating swap read fails is set to the >>> page table. So the swapcache page can be freed and the user won't end up >>> with a permanently mounted swap because a sector is bad. And if the page >>> is accessed later, the user process will be killed so that corrupted data >>> is never consumed. On the other hand, if the page is never accessed, the >>> user won't even notice it. >>> >>> Signed-off-by: Miaohe Lin >>> Acked-by: David Hildenbrand >> >> Hi Miaohe, >> >> This bug sounds relatively serious to me, and it seems old, so is it worth >> sending to -stable? > > I'm not sure if this is worth -stable, but no strong opinion. I have no strong opinion too. I'm just afraid someone might run into it. But swapoff is expected to be a rare operation anyway... > > The do_swap_page() part was added in 2005: > > commit b81074800b98ac50b64d4c8d34e8abf0fda5e3d1 > Author: Kirill Korotaev > Date: Mon May 16 21:53:50 2005 -0700 > > [PATCH] do_swap_page() can map random data if swap read fails > > There is a bug in do_swap_page(): 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 send SIGBUS in case of error. > > Signed-Off-By: Kirill Korotaev > Signed-Off-By: Alexey Kuznetsov > Acked-by: Hugh Dickins > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > > So the do_swap_page() part has been fixed for quite a while already. Does this mean only do_swap_page maps random data if swap read fails is observed from that time on? So this might not be worth -stable as it's never seen more than a decade? Thanks! >