From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 2D9D66B003D for ; Fri, 13 Mar 2009 15:27:59 -0400 (EDT) Received: by fxm26 with SMTP id 26so2775233fxm.38 for ; Fri, 13 Mar 2009 12:27:56 -0700 (PDT) Date: Fri, 13 Mar 2009 22:35:00 +0300 From: Alexey Dobriyan Subject: Re: How much of a mess does OpenVZ make? ;) Was: What can OpenVZ do? Message-ID: <20090313193500.GA2285@x200.localdomain> References: <1234479845.30155.220.camel@nimitz> <20090226155755.GA1456@x200.localdomain> <20090310215305.GA2078@x200.localdomain> <49B775B4.1040800@free.fr> <20090312145311.GC12390@us.ibm.com> <1236891719.32630.14.camel@bahia> <20090312212124.GA25019@us.ibm.com> <604427e00903122129y37ad791aq5fe7ef2552415da9@mail.gmail.com> <20090313053458.GA28833@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Linus Torvalds Cc: Sukadev Bhattiprolu , Ying Han , "Serge E. Hallyn" , linux-api@vger.kernel.org, containers@lists.linux-foundation.org, hpa@zytor.com, linux-kernel@vger.kernel.org, Dave Hansen , linux-mm@kvack.org, viro@zeniv.linux.org.uk, mingo@elte.hu, mpm@selenic.com, Andrew Morton , xemul@openvz.org, tglx@linutronix.de List-ID: On Fri, Mar 13, 2009 at 10:27:54AM -0700, Linus Torvalds wrote: > On Thu, 12 Mar 2009, Sukadev Bhattiprolu wrote: > > > Ying Han [yinghan@google.com] wrote: > > | Hi Serge: > > | I made a patch based on Oren's tree recently which implement a new > > | syscall clone_with_pid. I tested with checkpoint/restart process tree > > | and it works as expected. > > > > Yes, I think we had a version of clone() with pid a while ago. > > Are people _at_all_ thinking about security? > > Obviously not. For the record, OpenVZ always have CAP_SYS_ADMIN check on restore. And CAP_SYS_ADMIN will be in version to be sent out. Not having it is one big security hole. > There's no way we can do anything like this. Sure, it's trivial to do > inside the kernel. But it also sounds like a _wonderful_ attack vector > against badly written user-land software that sends signals and has small > races. > > Quite frankly, from having followed the discussion(s) over the last few > weeks about checkpoint/restart in various forms, my reaction to just about > _all_ of this is that people pushing this are pretty damn borderline. > > I think you guys are working on all the wrong problems. > > Let's face it, we're not going to _ever_ checkpoint any kind of general > case process. Just TCP makes that fundamentally impossible in the general > case, and there are lots and lots of other cases too (just something as > totally _trivial_ as all the files in the filesystem that don't get rolled > back). What do you mean here? Unlinked files? > So unless people start realizing that > (a) processes that want to be checkpointed had better be ready and aware > of it, and help out This is not going to happen. Userspace authors won't do anything (nor they shouldn't). > (b) there's no way in hell that we're going to add these kinds of > interfaces that have dubious upsides (just teach the damn program > you're checkpointing that pids will change, and admit to everybody > that people who want to be checkpointed need to do work) and are > potential security holes. I personally don't understand why on earth clone_with_pid() is again with us. As if pids are somehow unique among other resources. It was discussed when IPC objects creation with specific parameters were discussed. "struct pid" and "struct pid_namespace" can be trivially restored without leaking to userspace. People probably assume that task should be restored with clone(2) which is unnatural given relations between task_struct, nsproxy and individual struct foo_namespace's > (c) if you are going to play any deeper games, you need to have > privileges. IOW, "clone_with_pid()" is ok for _root_, but not for > some random user. And you'd better keep that in mind EVERY SINGLE > STEP OF THE WAY. > > I'm really fed up with these discussions. I have seen almost _zero_ > critical thinking at all. Probably because anybody who is in the least > doubtful about it simply has tuned out the discussion. So here's my input: > start small, start over, and start thinking about other issues than just > checkpointing. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org