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 77E2EC433EF for ; Wed, 6 Apr 2022 08:48:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C1F966B0072; Wed, 6 Apr 2022 04:48:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BCF646B0073; Wed, 6 Apr 2022 04:48:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ABDF06B0074; Wed, 6 Apr 2022 04:48:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0209.hostedemail.com [216.40.44.209]) by kanga.kvack.org (Postfix) with ESMTP id 9D88B6B0072 for ; Wed, 6 Apr 2022 04:48:08 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 53792AB9A0 for ; Wed, 6 Apr 2022 08:47:58 +0000 (UTC) X-FDA: 79325826636.26.A2F1B30 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf21.hostedemail.com (Postfix) with ESMTP id 5E1501C0017 for ; Wed, 6 Apr 2022 08:47:57 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KYJ5F57xNzgYR6; Wed, 6 Apr 2022 16:46:09 +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; Wed, 6 Apr 2022 16:47:53 +0800 Subject: Re: [PATCH] mm/swapfile: unuse_pte can map random data if swap read fails To: Matthew Wilcox , David Hildenbrand CC: , , References: <20220401072926.45051-1-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: <23943d63-1fc4-68ce-938f-0f9b53950710@huawei.com> Date: Wed, 6 Apr 2022 16:47:52 +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: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Stat-Signature: rf1dk1gufesu8b3nfq4jehezt9qkngwz Authentication-Results: imf21.hostedemail.com; dkim=none; spf=pass (imf21.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 5E1501C0017 X-HE-Tag: 1649234877-844493 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 2022/4/4 22:11, Matthew Wilcox wrote: > On Mon, Apr 04, 2022 at 03:37:36PM +0200, David Hildenbrand wrote: >> On 01.04.22 09:29, 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. >>> >>> Signed-off-by: Miaohe Lin >>> --- >>> mm/swapfile.c | 4 ++++ >>> 1 file changed, 4 insertions(+) >>> >>> diff --git a/mm/swapfile.c b/mm/swapfile.c >>> index 63c61f8b2611..e72a35de7a0f 100644 >>> --- 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; >>> + } >> >> Yeah, we have the same handling in do_swap_page(), whereby we send a >> SIGBUS because we're dealing with an actual access. >> >> Interestingly, folio_test_uptodate() states: >> >> "Anonymous and CoW folios are always uptodate." >> >> @Willy, is that true or is the swapin case not documented there? > > Why do we keep a !Uptodate page in the swap cache? If it can't be > read in from swap, I thought we just freed the page. Since Miaohe We could free the bad page. But we still need a way to prevent user from accessing the wrong data. > has observed that not happening, I guess it doesn't work that way, > but why not make it work that way? How could we make it work that way? Could you please tell me in more detail? Or any suggestions? Many thanks! > > . >