From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030393AbWGTWrZ (ORCPT ); Thu, 20 Jul 2006 18:47:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030396AbWGTWrZ (ORCPT ); Thu, 20 Jul 2006 18:47:25 -0400 Received: from coyote.holtmann.net ([217.160.111.169]:52456 "EHLO mail.holtmann.net") by vger.kernel.org with ESMTP id S1030393AbWGTWrY (ORCPT ); Thu, 20 Jul 2006 18:47:24 -0400 Subject: Re: Bad ext3/nfs DoS bug From: Marcel Holtmann To: Neil Brown Cc: Jan Kara , James <20@madingley.org>, linux-kernel@vger.kernel.org, akpm@osdl.org, sct@redhat.com In-Reply-To: <17599.2754.962927.627515@cse.unsw.edu.au> References: <20060717130128.GA12832@circe.esc.cam.ac.uk> <1153209318.26690.1.camel@localhost> <20060718145614.GA27788@circe.esc.cam.ac.uk> <1153236136.10006.5.camel@localhost> <20060718152341.GB27788@circe.esc.cam.ac.uk> <1153253907.21024.25.camel@localhost> <20060719092810.GA4347@circe.esc.cam.ac.uk> <20060719155502.GD3270@atrey.karlin.mff.cuni.cz> <17599.2754.962927.627515@cse.unsw.edu.au> Content-Type: text/plain Date: Fri, 21 Jul 2006 02:42:13 +0200 Message-Id: <1153442533.5050.1.camel@aeonflux.holtmann.net> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Neil, > > > So what happens next? Is the ext3 maintainer on sabatical, > > > or am I expected to submit a patch to fix this? > > I guess people are mostly busy with OLS and such so maybe they missed > > the discussion.. Giving CC to relevant people to catch their attention > > :) > > Andrew, Stephen: James has come across a nasty bug (potentially remote > > DoS). NFS extracts inode number from a filehandle and the inode number > > eventually ends in ext3_read_inode(). Now if the inode number is bogus, > > ext3_get_inode_block() calls ext3_error() and filesystem is remounted > > RO or whatever else is configured. That is quite undesirable in this > > case. > > Now the easy "fix" is to change ext3_error() to ext3_warning() but an > > attacker flooding your logs with warnings is probably not good either > > and in case the inode number comes from ext3 itself we should really do > > ext3_error() as there is some corruption in the fs. > > Better fix would be to add a flag to read_inode() saying that the inode > > number is from untrusted source (but that means changing a prototype of a > > function every fs uses) and change export_iget() to pass this flag. Yet > > another solution would be to make ext3 implement its own get_dentry() export > > function and pass the flag internally... > > What do you think is the best solution? > > I think that a good solution (hard to say if it is the best) is to > remove that error message altogether, and put it where inode numbers > are read out of directories. Something like the following patch - > compile tested only. I tested your patch and it works for me. So can someone with ext3 knowledge review and then propose it for upstream inclusion. Regards Marcel