Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754697AbZKII6L (ORCPT ); Mon, 9 Nov 2009 03:58:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754479AbZKII6K (ORCPT ); Mon, 9 Nov 2009 03:58:10 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:58416 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754407AbZKII6J (ORCPT ); Mon, 9 Nov 2009 03:58:09 -0500 Date: Mon, 9 Nov 2009 09:58:03 +0100 From: Pavel Machek To: "Eric W. Biederman" Cc: Miklos Szeredi , Alan Cox , akpm@linux-foundation.org, viro@ZenIV.linux.org.uk, dhowells@redhat.com, hch@infradead.org, adilger@sun.com, mtk.manpages@gmail.com, torvalds@linux-foundation.org, drepper@gmail.com, jamie@shareable.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 resend] vfs: new O_NODE open flag Message-ID: <20091109085803.GF4818@elf.ucw.cz> References: <20091105131545.72b4e319@lxorguk.ukuu.org.uk> <20091106141742.GA1428@ucw.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2099 Lines: 47 On Fri 2009-11-06 12:55:33, Eric W. Biederman wrote: > Pavel Machek writes: > > > On Thu 2009-11-05 15:27:06, Miklos Szeredi wrote: > >> On Thu, 5 Nov 2009, Alan Cox wrote: > >> > > - re-opening normally after checking file type (there's a debate > >> > > whether this would have security issues, but currently we do allow > >> > > re-opening with increased permissions thorugh /proc/*/fd) > >> > > >> > Which has already been demonstrated to be an (unfixed) security hole. > >> > >> No it hasn't :) Jamie theorized that there *might* be a real world > >> situation where the application writer didn't anticipate this > >> behavior. But as to actual demonstration, we have not seen one yet, I > >> think. > > > > See bugtraq, or lkml thread about symlinks with permissions. There's > > demo script there. > > Exactly a theoretical discussion, that demonstrates user space > applications with security holes can be written if they make > assumptions about the world that are not true. > > So far no one who believes this to be a security hole has found it > worth their while to look at nd->intent.open in proc_pid_follow_link > and write a patch. Pavel you started out asking for help on how > to do that and I think I have answered the original question. > I am tired of the whining. If no one who is persuaded the kernel is > wrong can be bothered to write a possibly buggy 5 line patch this is > clearly not a security hole. "I did not get a patch so it can't be security hole". Interesting. I still hope to write it one day, but as I do not have untrusted users on my systems, it is not particulary urgent. (And I still hope distro security people do they job.) Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/