Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754121AbbBTJdn (ORCPT ); Fri, 20 Feb 2015 04:33:43 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43478 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753092AbbBTJdl (ORCPT ); Fri, 20 Feb 2015 04:33:41 -0500 Message-ID: <1424424805.2632.24.camel@pluto.fritz.box> Subject: Re: [RFC PATCH 5/8] KEYS: exec request-key within the requesting task's init namespace From: Ian Kent To: "J. Bruce Fields" Cc: David Howells , Kernel Mailing List , Oleg Nesterov , Trond Myklebust , Benjamin Coddington , Al Viro , Jeff Layton , "Eric W. Biederman" Date: Fri, 20 Feb 2015 17:33:25 +0800 In-Reply-To: <20150219013116.GA13131@fieldses.org> References: <20150205023423.8382.69433.stgit@pluto.fritz.box> <20150205021553.8382.16297.stgit@pluto.fritz.box> <12365.1423149270@warthog.procyon.org.uk> <1423187245.3299.37.camel@pluto.fritz.box> <20150218170620.GI4148@fieldses.org> <20150218173132.GJ4148@fieldses.org> <20150218205908.GB12573@fieldses.org> <1424306341.2649.12.camel@pluto.fritz.box> <20150219013116.GA13131@fieldses.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5019 Lines: 107 On Wed, 2015-02-18 at 20:31 -0500, J. Bruce Fields wrote: > On Thu, Feb 19, 2015 at 08:39:01AM +0800, Ian Kent wrote: > > On Wed, 2015-02-18 at 15:59 -0500, J. Bruce Fields wrote: > > > On Wed, Feb 18, 2015 at 12:31:32PM -0500, J. Bruce Fields wrote: > > > > On Wed, Feb 18, 2015 at 12:06:20PM -0500, J. Bruce Fields wrote: > > > > > On Fri, Feb 06, 2015 at 09:47:25AM +0800, Ian Kent wrote: > > > > > > On Thu, 2015-02-05 at 15:14 +0000, David Howells wrote: > > > > > > > > > > > > > > > + /* If running within a container use the container namespace */ > > > > > > > > + if (current->nsproxy->net_ns != &init_net) > > > > > > > > > > > > > > Is that a viable check? Is it possible to have a container that shares > > > > > > > networking details? > > > > > > > > > > > > That's up for discussion. > > > > > > > > > > > > I thought about it and concluded that the check is probably not > > > > > > sufficient for any of the cases. > > > > > > > > > > > > I left it like that because I'm not sure exactly what the use cases are, > > > > > > hoping it promote discussion and here we are. > > > > > > > > > > > > I also think the current container environments don't share net > > > > > > namespace with the root init net namspace, necessarily, because thy are > > > > > > containers, ;) > > > > > > > > > > > > TBH I haven't looked at the user space container creation code but I > > > > > > expect it could be done that way if it was needed, so the answer is yes > > > > > > and no, ;) > > > > > > > > > > > > The questions then are do we need to check anything else, and what > > > > > > environment should the callback use in the different cases, and what > > > > > > other cases might break if we change it? > > > > > > > > > > > > For example, should the fs namespace also be checked for all of these > > > > > > cases, since we're executing a callback, or is whatever that's set to in > > > > > > the container always what's required for locating the executable. > > > > > > > > > > What would be the disadvantage of setting UMH_USE_NS unconditionally > > > > > here? > > > > > > > > In the nfs idmapping case, the mapping is per-nfs_client. > > > > > > > > Can nfs_idmap_new be the one that calls umh_get_init_task, with the > > > > corresponding put done in nfs_idmap_delete, or is there some reason that > > > > doesn't work? > > > > > > It's confusing sorting out possible use cases, but I think both of these > > > are reasonable: > > > > > > - mount an nfs filesystem from the host, then spawn containers > > > that all use that filesystem. > > > - mount an nfs filesystem from within a container. > > > > > > Your approach might work for the second, but in the first case we'll end > > > up with idmappers from multiple containers all trying to do the > > > idmapping for the shared filesystem. > > > > These patches are examples for context. > > > > Working out whether to run in a namespace or not was always going to be > > difficult, specifically for the case you point out. Maybe we can make > > use of some other information, namespace information in the super block > > perhaps, or something else, or perhaps we will need to add some > > information for this, not sure yet. We'll need to work together on that. > > > > TBH, I'm not that focused on the use cases because the base > > implementation is still undergoing significant change although I believe > > the use of a flag to request namespace execution is a good approach. > > That probably won't change. > > The flag requests that we use the container of the currently executing > task. In neither the nfs idmapper nor the nfsd state-recovery case is > that the correct choice. There's a bit more to do but I've done the changes arising from Oleg's comments so I've turned my attention to the recent discussion here. Please understand that I added the example usage patches largely to get this sort of comment because I was pretty sure there would be more to it than what was in the patches. I still don't fully understand the requirements so lets talk about them and to start with the former case above. I think your right that something needs to be saved in order to be able to make a decision at access time in a container. That might be as simple as working out whether the nn->umh_flags needs UMH_USE_NS at a different time, say at mount time. Taking a reference to something like the net namespace probably isn't necessary. But I don't understand the relationship between the net namespace (eg. is there a dependency on rpc requests and what the helper needs to do), the user in a container, and the idmapper operation. Can you help with that please. The case of nfsd state-recovery might be similar but you'll need to help me out a bit with that too. Ian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/