Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752793Ab3JEXR6 (ORCPT ); Sat, 5 Oct 2013 19:17:58 -0400 Received: from mail-ve0-f177.google.com ([209.85.128.177]:45118 "EHLO mail-ve0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752390Ab3JEXR4 (ORCPT ); Sat, 5 Oct 2013 19:17:56 -0400 MIME-Version: 1.0 In-Reply-To: <1381014462.1974.162@driftwood> References: <87li281wx6.fsf_-_@xmission.com> <1381014462.1974.162@driftwood> Date: Sat, 5 Oct 2013 16:17:55 -0700 X-Google-Sender-Auth: 3F3Uwu_Cf9NMG2cSSHfTgOhgu88 Message-ID: Subject: Re: [RFC][PATCH 0/3] vfs: Detach mounts on unlink. From: Linus Torvalds To: Rob Landley Cc: "Eric W. Biederman" , Miklos Szeredi , "Serge E. Hallyn" , Al Viro , Linux-Fsdevel , Kernel Mailing List , Andy Lutomirski Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1489 Lines: 43 On Sat, Oct 5, 2013 at 4:07 PM, Rob Landley wrote: > > A todo item I've had _forever_ is fixing chroot() to not be broken so that > you can trivially break out of a chroot via: What drugs are you on? Your example is moronic, and against all _documented_ uses of chroot. > chdir("/"); > mkdir("sub"); > chroot("sub"); > chdir("./../../../../../../../.."); After you do a chroot(), you need to chdir *into* the root. The reason chroot() itself doesn't do that is simple: you may still be doing various setup stuff. But your example is just stupid. Yes, chroot'ed environments can generally be escaped, but your example escape is simply because you didn't use chroot() correctly. So learn this pattern: every time you use chroot, add a simple chdir("/"); immediately after the chroot call. Then, if you decide that you want to do some setup in between the two (like the interface allows), that's fine, but always start off with that "chroot+chdir" pattern. (Similarly, if it turns out that you want to chdir somewhere else, like "/home/user" after the chroot, then you can obviously remove the now superfluous chdir("/"), but you always conceptually start off with that chroot/chdir pair) Linus -- 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/