From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id D9A786B004D for ; Fri, 13 Mar 2009 13:37:39 -0400 (EDT) Date: Fri, 13 Mar 2009 10:27:54 -0700 (PDT) From: Linus Torvalds Subject: Re: How much of a mess does OpenVZ make? ;) Was: What can OpenVZ do? In-Reply-To: <20090313053458.GA28833@us.ibm.com> Message-ID: References: <1234475483.30155.194.camel@nimitz> <20090212141014.2cd3d54d.akpm@linux-foundation.org> <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 Sender: owner-linux-mm@kvack.org To: Sukadev Bhattiprolu Cc: 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, Alexey Dobriyan List-ID: 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. 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). So unless people start realizing that (a) processes that want to be checkpointed had better be ready and aware of it, and help out (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. (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. Linus -- 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