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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0939C433EF for ; Tue, 26 Oct 2021 02:18:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CBF016103B for ; Tue, 26 Oct 2021 02:18:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233733AbhJZCUn (ORCPT ); Mon, 25 Oct 2021 22:20:43 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:14864 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230216AbhJZCUj (ORCPT ); Mon, 25 Oct 2021 22:20:39 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Hdb8M2cNzz90R4; Tue, 26 Oct 2021 10:18:11 +0800 (CST) Received: from kwepemm600015.china.huawei.com (7.193.23.52) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Tue, 26 Oct 2021 10:18:13 +0800 Received: from [10.174.176.52] (10.174.176.52) by kwepemm600015.china.huawei.com (7.193.23.52) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Tue, 26 Oct 2021 10:18:12 +0800 Subject: Re: [PATCH 4.19,v2] VFS: Fix fuseblk memory leak caused by mount concurrency To: Greg KH CC: , , , , , , , References: <20211013095101.641329-1-chenxiaosong2@huawei.com> <429d87b0-3a53-052a-a304-0afa8d51900d@huawei.com> <860c36c4-3668-1388-66d1-a07d463c2ad9@huawei.com> From: "chenxiaosong (A)" Message-ID: <209361bb-9e15-ebaf-2ff8-5846d5bfbbc2@huawei.com> Date: Tue, 26 Oct 2021 10:18:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.176.52] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm600015.china.huawei.com (7.193.23.52) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/10/20 20:30, Greg KH 写道: > On Wed, Oct 13, 2021 at 06:49:06PM +0800, chenxiaosong (A) wrote: >> 在 2021/10/13 18:38, chenxiaosong (A) 写道: >>> 在 2021/10/13 18:11, Greg KH 写道: >>>> On Wed, Oct 13, 2021 at 05:51:01PM +0800, ChenXiaoSong wrote: >>>>> If two processes mount same superblock, memory leak occurs: >>>>> >>>>> CPU0               |  CPU1 >>>>> do_new_mount       |  do_new_mount >>>>>    fs_set_subtype   |    fs_set_subtype >>>>>      kstrdup        | >>>>>                     |      kstrdup >>>>>      memrory leak   | >>>>> >>>>> Fix this by adding a write lock while calling fs_set_subtype. >>>>> >>>>> Linus's tree already have refactoring patchset [1], one of them >>>>> can fix this bug: >>>>>          c30da2e981a7 (fuse: convert to use the new mount API) >>>>> >>>>> Since we did not merge the refactoring patchset in this branch, >>>>> I create this patch. >>>>> >>>>> [1] https://patchwork.kernel.org/project/linux-fsdevel/patch/20190903113640.7984-3-mszeredi@redhat.com/ >>>>> >>>>> >>>>> Fixes: 79c0b2df79eb (add filesystem subtype support) >>>>> Cc: David Howells >>>>> Signed-off-by: ChenXiaoSong >>>>> --- >>>>> v1: Can not mount sshfs ([PATCH linux-4.19.y] VFS: Fix fuseblk >>>>> memory leak caused by mount concurrency) >>>>> v2: Use write lock while writing superblock >>>>> >>>>>   fs/namespace.c | 9 ++++++--- >>>>>   1 file changed, 6 insertions(+), 3 deletions(-) >>>> >>>> As you are referring to a fuse-only patch above, why are you trying to >>>> resolve this issue in the core namespace code instead? >>>> >>>> How does fuse have anything to do with this? >>>> >>>> confused, >>>> >>>> greg k-h >>>> . >>>> >>> >>> Now, only `fuse_fs_type` and `fuseblk_fs_type` has `FS_HAS_SUBTYPE` flag >>> in kernel code, but maybe there is a filesystem module(`struct >>> file_system_type` has `FS_HAS_SUBTYPE` flag). And only mounting fuseblk >>> filesystem(e.g. ntfs) will occur memory leak now. >> >> How about updating the subject as: VFS: Fix memory leak caused by mounting >> fs with subtype concurrency? > > That would be a better idea, but still, this is not obvious that this is > the correct fix at all... > . > Why is this patch not correct? Can you tell me more about it? Thanks.