Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755025AbaDYUqp (ORCPT ); Fri, 25 Apr 2014 16:46:45 -0400 Received: from mail-vc0-f173.google.com ([209.85.220.173]:47390 "EHLO mail-vc0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753676AbaDYUqo (ORCPT ); Fri, 25 Apr 2014 16:46:44 -0400 MIME-Version: 1.0 In-Reply-To: <87tx9h2m2w.fsf@x220.int.ebiederm.org> References: <87ha5h42va.fsf@x220.int.ebiederm.org> <87tx9h2m2w.fsf@x220.int.ebiederm.org> From: Andy Lutomirski Date: Fri, 25 Apr 2014 13:46:23 -0700 Message-ID: Subject: Re: pid ns feature request To: "Eric W. Biederman" Cc: "linux-kernel@vger.kernel.org" , "Serge E. Hallyn" , Linux Containers Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 25, 2014 at 1:25 PM, Eric W. Biederman wrote: > Andy Lutomirski writes: > >> On Fri, Apr 25, 2014 at 12:37 PM, Eric W. Biederman >> wrote: >>> Andy Lutomirski writes: >>> >>>> Unless I'm missing some trick, it's currently rather painful to mount >>>> a namespace /proc. You have to actually be in the pid namespace to >>>> mount the correct /proc instance, and you can't unmount the old /proc >>>> until you've mounted the new /proc. This means that you have to fork >>>> into the new pid namespace before you can finish setting it up. >>> >>> Yes. You have to be inside just about all namespaces before you can >>> finish setting them up. >>> >>> I don't know the context in which needed to be inside the pid namespace >>> is a burden. >> >> I'm trying to sandbox myself. I unshare everything, setup up new >> mounts, pivot_root, umount the old stuff, fork, and wait around for >> the child to finish. >> >> This doesn't work: the parent can't mount the new /proc, and the child >> can't either because it's too late. >> >> The only solution I can think of without kernel changes is to fork the >> child (pid 1) before pivot_root, which makes everything more >> complicated. I suppose I can unshare, fork immediately, have the >> child set up all the mounts, and then wake the parent, but this is an >> annoying bit of extra complexity for no obvious gain. > > Or perhaps just use clone and clone flags. > > What are you doing with the parent process? What value does it serve? I'm not entirely sure. I'm hacking on this thing: https://github.com/amluto/sandstorm/tree/userns which isn't really my code. But there's an inner sandbox and an outer sandbox, and only the inner sandbox is in a pid namespace. I suppose what what I'm doing is a bit strange. --Andy -- 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/