Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755738AbZJ1VG1 (ORCPT ); Wed, 28 Oct 2009 17:06:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754903AbZJ1VG0 (ORCPT ); Wed, 28 Oct 2009 17:06:26 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:39227 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754108AbZJ1VGZ (ORCPT ); Wed, 28 Oct 2009 17:06:25 -0400 Date: Wed, 28 Oct 2009 22:06:24 +0100 From: Pavel Machek To: Casey Schaufler Cc: "Eric W. Biederman" , Trond Myklebust , Jan Kara , "J. Bruce Fields" , "Serge E. Hallyn" , kernel list , linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, jamie@shareable.org Subject: Re: symlinks with permissions Message-ID: <20091028210623.GB4159@elf.ucw.cz> References: <20091025062953.GC1391@ucw.cz> <20091026163157.GB7233@duck.suse.cz> <20091026165729.GF23564@us.ibm.com> <20091026173629.GB16861@fieldses.org> <20091026174631.GD7233@duck.suse.cz> <1256579869.8576.7.camel@heimdal.trondhjem.org> <20091025093604.GA1501@ucw.cz> <20091028081653.GA18290@elf.ucw.cz> <4AE87292.20802@schaufler-ca.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4AE87292.20802@schaufler-ca.com> 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: 1212 Lines: 30 > > Please see bugtraq discussion at > > http://seclists.org/bugtraq/2009/Oct/179 . > > > > (In short, you get read-only fd, and you can upgrade it to read-write > > fd. Yes, you are the owner of the process, but you are not owner of > > the file the fd refers to.) > > > > The actual permissions of the file are not ignored, but permissions of > > the containing directory _are_. If there's 666 file in 700 directory, > > you can reopen it read-write, in violation of directory's 700 > > permissions. > > There is no security violation here. Consider the case where You are able to write to my files, when unix permissions forbid that. How do you call that? Strange behaviour of /proc/*/fd/ symlink that is not really a symlink allows that. See bugtraq discussion at http://seclists.org/bugtraq/2009/Oct/179 . 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/