From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755942AbcECLXg (ORCPT ); Tue, 3 May 2016 07:23:36 -0400 Received: from out5-smtp.messagingengine.com ([66.111.4.29]:32775 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755328AbcECLXf (ORCPT ); Tue, 3 May 2016 07:23:35 -0400 Message-Id: <1462274614.1336993.596603129.675ECADD@webmail.messagingengine.com> X-Sasl-Enc: IWCWFl5Lmhslyb4vnTUyEPFR5p3gqw56yeJQhduAke11 1462274614 From: Hannes Frederic Sowa To: Richard Weinberger , Guillaume Nault Cc: Wang Shanker , netdev@vger.kernel.org, LKML MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain X-Mailer: MessagingEngine.com Webmail Interface - ajax-730e9430 Subject: Re: [Question] Should `CAP_NET_ADMIN` be needed when opening `/dev/ppp`? Date: Tue, 03 May 2016 13:23:34 +0200 In-Reply-To: References: <2BEB0C68-EBC6-4A8F-A751-DE8F4A2C9D2C@gmail.com> <20160503101240.GA1304@alphalink.fr> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 3, 2016, at 12:35, Richard Weinberger wrote: > On Tue, May 3, 2016 at 12:12 PM, Guillaume Nault > wrote: > > On Sun, May 01, 2016 at 09:38:57PM +0800, Wang Shanker wrote: > >> static int ppp_open(struct inode *inode, struct file *file) > >> { > >> /* > >> * This could (should?) be enforced by the permissions on /dev/ppp. > >> */ > >> if (!capable(CAP_NET_ADMIN)) > >> return -EPERM; > >> return 0; > >> } > >> ``` > >> > >> I wonder why CAP_NET_ADMIN is needed here, rather than leaving it to the > >> permission of the device node. If there is no need, I suggest that the > >> CAP_NET_ADMIN check be removed. > >> > > If this test was removed here, then it'd have to be added again in the > > PPPIOCNEWUNIT ioctl, at the very least, because creating a netdevice > > should require CAP_NET_ADMIN. Therefore that wouldn't help for your > > case. > > I don't know why the test was placed in ppp_open() in the first place, > > but changing it now would have side effects on user space. So I'd > > rather leave the code as is. > > I think the question is whether we really require having CAP_NET_ADMIN > in the initial namespace and not just in the current one. > Is ppp not network namespace aware? I agree, ns_capable(net->user_ns, CAP_NET_ADMIN), would probably make more sense. Bye, Hannes