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 018D0C28D13 for ; Tue, 23 Aug 2022 01:43:03 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 435F16B0073; Mon, 22 Aug 2022 21:43:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3E4D46B0074; Mon, 22 Aug 2022 21:43:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2ADC78D0001; Mon, 22 Aug 2022 21:43:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 170AD6B0073 for ; Mon, 22 Aug 2022 21:43:03 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id CBFE6A8971 for ; Tue, 23 Aug 2022 01:43:02 +0000 (UTC) X-FDA: 79829159004.24.29C4FD9 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf03.hostedemail.com (Postfix) with ESMTP id 0317D20039 for ; Tue, 23 Aug 2022 01:43:01 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4MBX486msQznThm; Tue, 23 Aug 2022 09:40:40 +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; Tue, 23 Aug 2022 09:42:58 +0800 Subject: Re: [PATCH 4/6] mm: hugetlb_vmemmap: add missing smp_wmb() before set_pte_at() To: Muchun Song CC: Andrew Morton , Mike Kravetz , Muchun Song , Linux MM , References: <20220816130553.31406-1-linmiaohe@huawei.com> <20220816130553.31406-5-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Tue, 23 Aug 2022 09:42:57 +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 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661218982; a=rsa-sha256; cv=none; b=wACg0IwInae/1Qx26bMwiGBFms51YtZ7pjAmfPX41lCxJX/n4F4B2lpjsZrKB4Rg9QTNDr 7twbPv5CUVnbD3fq53h5mwtB030YaIQ6mPOIVHnhFrsbiFbqpVBVHXZ9nHf3H8yOJ2N1o6 rx6OyQOvN3vSoWEan5MqPgqhARIgoWo= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=none; spf=pass (imf03.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 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661218982; 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=pZPERbt6az6SGXWrt6ZEG63pjKPucmP+5f1tudmoh4I=; b=gWvHncv+UMmP4crIgXaqgwzLXizLjh6C3+9vbpq5HIsaYA1xHlNqVNBOglVk71c+7NmJmx FhkfGXY8wRlfP989Kn5sIr8dM9z0gpmDDzgzGiCk4VqXkee6GFvRZhS5xYP3n9IDJxoUL1 gDAy8uDb6vmnmnjxyHQZe47Ihoyz4RQ= X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0317D20039 Authentication-Results: imf03.hostedemail.com; dkim=none; spf=pass (imf03.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-Stat-Signature: m3pyoq94an4tofaxkfsh7atd9k3eyba1 X-Rspam-User: X-HE-Tag: 1661218981-855030 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 2022/8/22 18:23, Muchun Song wrote: > > >> On Aug 22, 2022, at 16:45, Miaohe Lin wrote: >> >> On 2022/8/20 16:12, Muchun Song wrote: >>> >>> >>>> On Aug 16, 2022, at 21:05, Miaohe Lin wrote: >>>> >>>> The memory barrier smp_wmb() is needed to make sure that preceding stores >>>> to the page contents become visible before the below set_pte_at() write. >>> >>> I found another place where is a similar case. See kasan_populate_vmalloc_pte() in >>> mm/kasan/shadow.c. >> >> Thanks for your report. >> >>> >>> Should we fix it as well? >> >> I'm not familiar with kasan yet, but I think memory barrier is needed here or memory corrupt >> can't be detected until the contents are visible. smp_mb__after_atomic before set_pte_at should >> be enough? What's your opinion? > > I didn’t see any atomic operation between set_pte_at() and memset(), I don’t think > smp_mb__after_atomic() is feasible if we really need to insert a barrier. I suggest Oh, it should be smp_mb__after_spinlock(), i.e. something like below: diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c index 0e3648b603a6..38e503c89740 100644 --- a/mm/kasan/shadow.c +++ b/mm/kasan/shadow.c @@ -277,6 +277,7 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr, spin_lock(&init_mm.page_table_lock); if (likely(pte_none(*ptep))) { + smp_mb__after_spinlock(); set_pte_at(&init_mm, addr, ptep, pte); page = 0; } Does this make sense for you? > you to send a RFC patch to KASAN maintainers, they are more familiar with this than > us. Sounds like a good idea. Will do it. Thanks, Miaohe Lin