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 B7B8DC32771 for ; Fri, 19 Aug 2022 07:32:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D39FF8D0003; Fri, 19 Aug 2022 03:32:32 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CC22D8D0002; Fri, 19 Aug 2022 03:32:32 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B632C8D0003; Fri, 19 Aug 2022 03:32:32 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id A04178D0002 for ; Fri, 19 Aug 2022 03:32:32 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 7901BC015F for ; Fri, 19 Aug 2022 07:32:32 +0000 (UTC) X-FDA: 79815524544.27.99334D4 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf03.hostedemail.com (Postfix) with ESMTP id B719A2000A for ; Fri, 19 Aug 2022 07:32:30 +0000 (UTC) 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 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660894350; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MeHeNA0yiUFakOgBnB9erR+7xumNU15E3hj1r2Qz+L8=; b=TKMzYKwv1yRSDWLbjZUjkmUAUbmbwpoz9c/SeRd0DJWMvu0lf118vyNd8XwzaOjRtl56zF +y7Kp6q08EsQmAV3/9jeEgmWzy+DpEREYq3A++hbVJFPOogo16+qldvzGU2X8J+tSALvut YYeCuypA2X3bSEv1EZVgbsmw6m+i5JE= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf03.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660894350; a=rsa-sha256; cv=none; b=VibhI9GjENbcRIiXnV6vgQfWWNGPNMNgmPRnrvi5ArFO+cqZ1tYfK/5T4qmMY0+hlYxtjd H7r6YdX004uXXCyAmSDKD6C9HxdFGynExP0CD9qjJSVm0/i2kxhuIRxG7UBvzcMtp19b13 cB7iZcmAs02RQH3EsTTXsBiLc5dVROo= Authentication-Results: imf03.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf03.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: B719A2000A X-Stat-Signature: oqbmmw6r4d8fq9tqscgtckqazc9pexor X-Rspam-User: X-HE-Tag: 1660894350-338994 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 2022/8/19 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 >