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 39031C25B0E for ; Fri, 19 Aug 2022 07:32:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346453AbiHSHce (ORCPT ); Fri, 19 Aug 2022 03:32:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42980 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241976AbiHSHcb (ORCPT ); Fri, 19 Aug 2022 03:32:31 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D6C8FE3C09 for ; Fri, 19 Aug 2022 00:32:29 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4M8D0K2jjJzlWNN; Fri, 19 Aug 2022 15:29:21 +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; Fri, 19 Aug 2022 15:32:27 +0800 Subject: Re: [PATCH 4/6] mm, hwpoison: fix possible use-after-free in mf_dax_kill_procs() To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= CC: "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" References: <20220818130016.45313-1-linmiaohe@huawei.com> <20220818130016.45313-5-linmiaohe@huawei.com> <20220819052324.GD613144@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: <6dff6aec-833c-a3db-1180-09e395f6265a@huawei.com> Date: Fri, 19 Aug 2022 15:32:27 +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: <20220819052324.GD613144@hori.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) 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 2022/8/19 13:23, HORIGUCHI NAOYA(堀口 直也) wrote: > On Thu, Aug 18, 2022 at 09:00:14PM +0800, Miaohe Lin wrote: >> After kill_procs(), tk will be freed without being removed from the to_kill >> list. In the next iteration, the freed list entry in the to_kill list will >> be accessed, thus leading to use-after-free issue. > > kill_procs() runs over the to_kill list and frees all listed items in each > iteration. So just after returning from unmap_and_kill(), to_kill->next and > to_kill->prev still point to the addresses of struct to_kill which was the > first or last item (already freed!). This is bad-manered, but > collect_procs_fsdax() in the next iteration calls list_add_tail() and > overwrites the dangling pointers with newly allocated item. So this problem list_add_tail will do WRITE_ONCE(prev->next, new) where prev is already freed! Or am I miss something? > should not be so critical? Anyway, I agree with fixing this fragile code. > >> Fix it by reinitializing >> the to_kill list after unmap_and_kill(). >> >> Fixes: c36e20249571 ("mm: introduce mf_dax_kill_procs() for fsdax case") >> Signed-off-by: Miaohe Lin > >> --- >> mm/memory-failure.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index 7023c3d81273..a2f4e8b00a26 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -1658,6 +1658,8 @@ int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, >> collect_procs_fsdax(page, mapping, index, &to_kill); >> unmap_and_kill(&to_kill, page_to_pfn(page), mapping, >> index, mf_flags); >> + /* Reinitialize to_kill list for later resuing. */ > > s/resuing/reusing/ ? OK. > >> + INIT_LIST_HEAD(&to_kill); > > How about adding list_del() in kill_procs()? Other callers now use > to_kill only once, but fixing generally looks tidier to me. That's a good idea. Will do it in v2. Many thanks for your review, Naoya! Thanks, Miaohe Lin > > Thanks, > Naoya Horiguchi >