From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH 0/3] vfs: plug some holes involving LAST_BIND symlinks and file bind mounts (try #5) Date: Mon, 30 Nov 2009 13:28:51 +0100 Message-ID: <20091130122851.GF13328@elf.ucw.cz> References: <20091123173616.75c3f600@tlielax.poochiereds.net> <20091123224948.GB5598@shareable.org> <20091123181545.05ad004d@tlielax.poochiereds.net> <20091123193426.55f1530a@tlielax.poochiereds.net> <20091124012027.GA14645@shareable.org> <20091124062621.744beddb@tlielax.poochiereds.net> <20091124120906.GA1700@ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: jlayton@redhat.com, jamie@shareable.org, ebiederm@xmission.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, viro@ZenIV.linux.org.uk To: Miklos Szeredi Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Tue 2009-11-24 13:59:06, Miklos Szeredi wrote: > On Tue, 24 Nov 2009, Pavel Machek wrote: > > I believe that current semantics is ugly enough that 'documenting' it > > is not enough... and people want to port from other systems, too, not > > expecting nasty surprises like this... > > This hasn't been a problem for the last 12 years, and still we don't > see script kiddies exploiting this hole and sysadmins hurrying to > secure their system, even though it has been public for quite a while. > > Why? Because condition when it hits are quite unusual? > The reason might be, that there *is no* violation of security. Well, security people disagree with you. > See this: the surprise isn't that an inode can be reached from > multiple paths, that has been possible with hard links for as long as > unix lived. The suprise is that the inode can be reached through > proc. So this "hole" that has been opened about 12 years ago in linux > is quite well known. Only this particular aspect of it isn't well > known, but that doesn't mean it's not right, does it? It does. Bypassing checks on read-only file descriptors is design misfeature, and users are clearly unaware. (See bugtraq). Being "old" does not mean it is right. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html