Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932150AbZJ0ILs (ORCPT ); Tue, 27 Oct 2009 04:11:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932110AbZJ0ILr (ORCPT ); Tue, 27 Oct 2009 04:11:47 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:53131 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932109AbZJ0ILq (ORCPT ); Tue, 27 Oct 2009 04:11:46 -0400 Date: Tue, 27 Oct 2009 09:11:41 +0100 From: Pavel Machek To: Trond Myklebust Cc: 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: <20091027081141.GF5019@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> <1256581336.8576.20.camel@heimdal.trondhjem.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1256581336.8576.20.camel@heimdal.trondhjem.org> 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: 1130 Lines: 26 On Mon 2009-10-26 14:22:16, Trond Myklebust wrote: > On Sun, 2009-10-25 at 10:36 +0100, Pavel Machek wrote: > > Well, it is unexpected and mild security hole. > > > > Part of the problem is that even if you have read-only > > filedescriptor, you can upgrade it to read-write, even if path is > > inaccessible to you. > > > > So if someone passes you read-only filedescriptor, you can still write > > to it. > > If someone passes you a file descriptor, can't you in any case play > games with, openat(fd,"",O_RDWR), in order to achieve the same thing? I > must admit I haven't tried it yet, but at a first glance I can't see > anything that prevents me from doing this... According to my documentation, openat needs directory fd. 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/