From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752775AbeDMBZo (ORCPT ); Thu, 12 Apr 2018 21:25:44 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:52127 "EHLO huawei.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751775AbeDMBZn (ORCPT ); Thu, 12 Apr 2018 21:25:43 -0400 Subject: Re: [PATCH] f2fs: set deadline to drop expired inmem pages To: Jaegeuk Kim CC: , , References: <20180408081312.6190-1-yuchao0@huawei.com> <09fd3144-d1c5-ca02-178d-b467d6fbe0e1@huawei.com> <20180413010433.GB51348@jaegeuk-macbookpro.roam.corp.google.com> From: Chao Yu Message-ID: Date: Fri, 13 Apr 2018 09:25:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20180413010433.GB51348@jaegeuk-macbookpro.roam.corp.google.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/4/13 9:04, Jaegeuk Kim wrote: > On 04/10, Chao Yu wrote: >> Hi Jaegeuk, >> >> On 2018/4/8 16:13, Chao Yu wrote: >>> f2fs doesn't allow abuse on atomic write class interface, so except >>> limiting in-mem pages' total memory usage capacity, we need to limit >>> start-commit time as well, otherwise we may run into infinite loop >>> during foreground GC because target blocks in victim segment are >>> belong to atomic opened file for long time. >>> >>> Now, we will check the condition with f2fs_balance_fs_bg in >>> background threads, once if user doesn't commit data exceeding 30 >>> seconds, we will drop all cached data, so I expect it can keep our >>> system running safely to prevent Dos attack. >> >> Is it worth to add this patch to avoid abuse on atomic write interface by user? > > Hmm, hope to see a real problem first in this case. I think this can be a more critical security leak instead of a potential issue which we can wait for someone reporting that can be too late. For example, user can simply write a huge file whose data spread in all f2fs segments, once user open that file as atomic, foreground GC will suffer deadloop, causing denying any further service of f2fs. Thanks, > >> Thanks, > > . >