From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751823AbbDULbi (ORCPT ); Tue, 21 Apr 2015 07:31:38 -0400 Received: from szxga01-in.huawei.com ([58.251.152.64]:1892 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750872AbbDULbe (ORCPT ); Tue, 21 Apr 2015 07:31:34 -0400 Message-ID: <553634F1.6080106@huawei.com> Date: Tue, 21 Apr 2015 19:30:57 +0800 From: Wuqixuan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Richard Weinberger , Azat Khuzhin CC: Al Viro , linux-fsdevel , LKML Subject: Re: [PATCH] fs/sync.c : Add CAP_SYS_ADMIN checking before sync References: <552FA066.3010905@huawei.com> <20150416150847.GA16917@azat> In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.66.68.134] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks for your both replies. We will waiting for the patchset, and modify as per Richard's suggestion for temporary hack. On 2015/4/17 3:31, Richard Weinberger wrote: > On Thu, Apr 16, 2015 at 5:08 PM, Azat Khuzhin wrote: >> On Thu, Apr 16, 2015 at 07:43:34PM +0800, Wuqixuan wrote: >>> The process, supposed in one container, can't flush the metadata >>> and data of the all host's partitions without CAP_SYS_ADMIN >>> capability, like sys_mount is doing. The checking will prevent some >>> vicious programs impacting IO sequnces of those partitions, >>> particularly, the ones which can't be accessed in the container. >>> >>> Signed-off-by: Last Wu >>> --- >>> fs/sync.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/fs/sync.c b/fs/sync.c >>> index fbc98ee..9f07909 100644 >>> --- a/fs/sync.c >>> +++ b/fs/sync.c >>> @@ -103,6 +103,9 @@ SYSCALL_DEFINE0(sync) >>> { >>> int nowait = 0, wait = 1; >>> >>> + if (!capable(CAP_SYS_ADMIN)) >>> + return -EPERM; >> So after this patch I can't call sync as a regular user? (even without >> containers). >> But nothing in sync(2) says about special permissions for this. > Yeah, this solution will break userspace. > A much more generic solution would be to wait for cgroup aware writeback[1]. > As temporary hack you can check whether the calling process is in the > initial pid namesapce to detect > a container calling sync(2)... > > [1] https://lwn.net/Articles/628631/ >