From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oren Laadan Subject: Re: [PATCH] [RFC] c/r: Add UTS support Date: Wed, 18 Mar 2009 04:27:21 -0400 Message-ID: <49C0B069.6060300@cs.columbia.edu> References: <1236880612-15316-1-git-send-email-danms@us.ibm.com> <20090312162954.4a4b8e00@thinkcentre.lan> <87fxhipfrh.fsf@caffeine.danplanet.com> <20090312224820.GA12723@hallyn.com> <87bps6pcyf.fsf@caffeine.danplanet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87bps6pcyf.fsf-FLMGYpZoEPULwtHQx/6qkW3U47Q5hpJU@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Dan Smith Cc: containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org, Nathan Lynch List-Id: containers.vger.kernel.org Dan Smith wrote: > SH> Well it forces restart to go through the established userspace > SH> API's when creating resources (in this case, tasks and namespaces) > SH> which means any existing security guarantees are leveraged. > > That's a very valid point. However, it still seems unbalanced to make > checkpoint a completely in-kernel process and restart an odd mix of > the two with potentially more confusing semantics and requirements. > There are other reasons to allow restart to be not fully symmetric with respect to checkpoint. For example, if you have a smart(er) user space application that wants to provide the restart some of the resources pre-constructed, allowing much flexibility (already requested by people) for the restart provdure (E.g., when doing distributed checkpoint, or when restarting a special device whose). See my post: https://lists.linux-foundation.org/pipermail/containers/2009-March/016234.html Oren. > SH> If we go with your patch, we suddenly have to worry about whether > SH> restart is a way to get around the CAP_SYS_ADMIN requirements for > SH> cloning a new namespace. Just as an example. > > Why? The call to copy_namespaces() will do the CAP_SYS_ADMIN check, > right? Maybe your point is that in the restart implementation of > other namespace types we could potentially slide in a call to > something else that has already assumed the check has been made? I > think that doing the obligatory copy_namespaces() during the restart > helps catch that case early and explicitly, no? >