From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754356AbZJZSE4 (ORCPT ); Mon, 26 Oct 2009 14:04:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754291AbZJZSE4 (ORCPT ); Mon, 26 Oct 2009 14:04:56 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:40556 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753542AbZJZSEz (ORCPT ); Mon, 26 Oct 2009 14:04:55 -0400 Date: Sun, 25 Oct 2009 10:36:04 +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: <20091025093604.GA1501@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1256579869.8576.7.camel@heimdal.trondhjem.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 2009-10-26 13:57:49, Trond Myklebust wrote: > On Mon, 2009-10-26 at 18:46 +0100, Jan Kara wrote: > > That's what I'd think as well but it does not as I've just learned and > > tested :) proc_pid_follow_link actually directly gives a dentry of the > > target file without checking permissions on the way. It is weider. That symlink even has permissions. Those are not checked, either. > I seem to remember that is deliberate, the point being that a symlink > in /proc/*/fd/ may contain a path that refers to a private namespace. 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. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html