From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id 8B0CA6B004F for ; Tue, 30 Jun 2009 17:21:29 -0400 (EDT) MIME-Version: 1.0 Message-ID: Date: Tue, 30 Jun 2009 14:21:35 -0700 (PDT) From: Dan Magenheimer Subject: RE: [RFC] transcendent memory for Linux In-Reply-To: <4A493D19.4050908@goop.org> Content-Type: text/plain; charset=Windows-1252 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: Jeremy Fitzhardinge Cc: Pavel Machek , linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, npiggin@suse.de, chris.mason@oracle.com, kurt.hackel@oracle.com, dave.mccracken@oracle.com, Avi Kivity , Rik van Riel , alan@lxorguk.ukuu.org.uk, Rusty Russell , Martin Schwidefsky , akpm@osdl.org, Marcelo Tosatti , Balbir Singh , tmem-devel@oss.oracle.com, sunil.mushran@oracle.com, linux-mm@kvack.org, Himanshu Raj List-ID: > From: Jeremy Fitzhardinge [mailto:jeremy@goop.org] > On 06/29/09 14:57, Dan Magenheimer wrote: > > Interesting question. But, more than the 128-bit UUID must > > be guessed... a valid 64-bit object id and a valid 32-bit > > page index must also be guessed (though most instances of > > the page index are small numbers so easy to guess). Once > > 192 bits are guessed though, yes, the pages could be viewed > > and modified. I suspect there are much more easily targeted > > security holes in most data centers than guessing 192 (or > > even 128) bits. >=20 > If its possible to verify the uuid is valid before trying to find a > valid oid+page, then its much easier (since you can concentrate on the > uuid first). No, the uuid can't be verified. Tmem gives no indication as to whether a newly-created pool is already in use (shared) by another guest. So without both the 128-bit uuid and an already-in-use 64-bit object id and 32-bit page index, no data is readable or writable by the attacker. > You also have to consider the case of a domain which was once part of > the ocfs cluster, but now is not - it may still know the uuid, but not > be otherwise allowed to use the cluster. > If the uuid is derived from something like the > filesystem's uuid - which wouldn't normally be considered sensitive > information - then its not like its a search of the full=20 > 128-bit space.=20 > And even if it were secret, uuids are not generally 128=20 > randomly chosen bits. Hmmm... that is definitely a thornier problem. I guess the security angle definitely deserves more design. But, again, this affects only shared precache which is not intended to part of the proposed initial tmem patchset, so this is a futures issue.) Thanks again for the feedback! Dan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org