Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754001AbaJGNdn (ORCPT ); Tue, 7 Oct 2014 09:33:43 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:45542 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753952AbaJGNdl (ORCPT ); Tue, 7 Oct 2014 09:33:41 -0400 Date: Tue, 7 Oct 2014 14:33:39 +0100 From: Al Viro To: Andrey Vagin Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Andrey Vagin , Andrew Morton , "Eric W. Biederman" , Cyrill Gorcunov , Pavel Emelyanov , Serge Hallyn , Rob Landley Subject: Re: [PATCH] [RFC] mnt: add ability to clone mntns starting with the current root Message-ID: <20141007133339.GH7996@ZenIV.linux.org.uk> References: <1412683977-29543-1-git-send-email-avagin@openvz.org> <20141007133039.GG7996@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141007133039.GG7996@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 07, 2014 at 02:30:40PM +0100, Al Viro wrote: > On Tue, Oct 07, 2014 at 04:12:57PM +0400, Andrey Vagin wrote: > > Another problem is that rootfs can't be hidden from a container, because > > rootfs can't be moved or umounted. > > ... which is a bug in mntns_install(), AFAICS. Ability to get to exposed rootfs, that is. > > Here is an example how to get access to rootfs: > > fd = open("/proc/self/ns/mnt", O_RDONLY) > > umount2("/", MNT_DETACH); > > setns(fd, CLONE_NEWNS) > > > > rootfs may contain data, which should not be avaliable in CT-s. > > Indeed. ... and it looks like the above is what your mangled reproducer in previous patch had been made of - fd = open("/proc/self/ns/mnt", O_RDONLY) umount2("/", MNT_DETACH); setns(fd, CLONE_NEWNS) umount2("/", MNT_DETACH); IMO what it shows is setns() bug. This "switch root/cwd, no matter what" is wrong. -- 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/