Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757265AbXIYPUe (ORCPT ); Tue, 25 Sep 2007 11:20:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752858AbXIYPU1 (ORCPT ); Tue, 25 Sep 2007 11:20:27 -0400 Received: from sovereign.computergmbh.de ([85.214.69.204]:54774 "EHLO sovereign.computergmbh.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367AbXIYPU0 (ORCPT ); Tue, 25 Sep 2007 11:20:26 -0400 Date: Tue, 25 Sep 2007 17:20:25 +0200 (CEST) From: Jan Engelhardt To: David Newall cc: "Serge E. Hallyn" , Bill Davidsen , Philipp Marek , 7eggert@gmx.de, Alan Cox , majkls , bunk@fs.tum.de, linux-kernel@vger.kernel.org Subject: Re: Chroot bug (was: sys_chroot+sys_fchdir Fix) In-Reply-To: <46F924E3.50205@davidnewall.com> Message-ID: References: <56705.193.171.152.61.1190289559.squirrel@webmail.marek.priv.at> <46F29A9A.4070806@davidnewall.com> <200709201817.17282@x5> <46F2B59F.8090709@davidnewall.com> <46F2DDD0.3030500@tmr.com> <46F380E4.4040606@davidnewall.com> <20070924213215.GA32716@vino.hallyn.com> <46F83474.5040503@davidnewall.com> <20070924230008.GA3160@vino.hallyn.com> <46F8BC8A.7080006@davidnewall.com> <20070925114947.GA9721@vino.hallyn.com> <46F91417.9050600@davidnewall.com> <46F924E3.50205@davidnewall.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1566 Lines: 40 On Sep 26 2007 00:40, David Newall wrote: > > Miloslav Semler pointed out that a root process can chdir("..") out of its > chroot. Although this is documented in the man page, it conflicts with the > essential function, which is to change the root directory of the process. In > addition to any creative uses, for example Philipp Marek's loading dynamic > libraries, it seems clear that the prime purpose of chroot is to aid security. > Being able to cd your way out is handy for the bad guys, but the good guys > don't need it; there are a thousand better, safer solutions. So what? Just do this: chdir into the root after chroot. It won't conform to SVR4/4.4BSD anymore, but hey, let Linux set some sane standard ain't bad either. I doubt anyone really relies on the fact that after chroot, your cwd might be outside the root. Signed-off-by: Jan Engelhardt --- fs/open.c | 1 + 1 file changed, 1 insertion(+) Index: linux-2.6.23/fs/open.c =================================================================== --- linux-2.6.23.orig/fs/open.c +++ linux-2.6.23/fs/open.c @@ -547,6 +547,7 @@ asmlinkage long sys_chroot(const char __ set_fs_root(current->fs, nd.mnt, nd.dentry); set_fs_altroot(); + set_fs_pwd(current->fs, nd.mnt, nd.dentry); error = 0; dput_and_out: path_release(&nd); - 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/