From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joanna Rutkowska Subject: Re: Xen 4.0.0x allows for data corruption in Dom0 Date: Tue, 09 Mar 2010 00:56:22 +0100 Message-ID: <4B958EA6.9000106@invisiblethingslab.com> References: <20100307143631.GO2580@reaktio.net> <20100307161256.GQ2580@reaktio.net> <1268090552.27980.288.camel@agari.van.xensource.com> <4B958896.4090004@invisiblethingslab.com> <1268092325.27980.318.camel@agari.van.xensource.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0698778330==" Return-path: In-Reply-To: <1268092325.27980.318.camel@agari.van.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Daniel Stodden Cc: "xen-devel@lists.xensource.com" , Keir Fraser List-Id: xen-devel@lists.xenproject.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============0698778330== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig133F0ED8EB7A105BAF520697" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig133F0ED8EB7A105BAF520697 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 03/09/2010 12:52 AM, Daniel Stodden wrote: > On Mon, 2010-03-08 at 18:30 -0500, Joanna Rutkowska wrote: >> On 03/09/2010 12:22 AM, Daniel Stodden wrote: >>> On Sun, 2010-03-07 at 11:12 -0500, Pasi K=E4rkk=E4inen wrote: >>>> On Sun, Mar 07, 2010 at 02:39:09PM +0000, Keir Fraser wrote: >>>>> On 07/03/2010 14:36, "Pasi K=E4rkk=E4inen" wrote: >>>>> >>>>>>> Tried a few times and no luck reproducing so far. I hope some oth= er people >>>>>>> on the list also will give it a go, since it's so easy to try it = out. >>>>>>> >>>>>> >>>>>> I'm able to reproduce this with xen/master 2.6.31.6 dom0 kernel (f= rom >>>>>> 2010-02-20), >>>>>> but I'm not able to reproduce it with the current xen/stable 2.6.3= 2.9. >>>>>> >>>>>> I'll try with the most recent 2.6.31.6 dom0 kernel aswell.. >>>>> >>>>> Thanks Pasi! >>>>> >>>> >>>> It seems to happen with the latest xen/master 2.6.31.6 aswell! >>> >>> Does this look to you like we're corrupting memory or on-disk storage= ? >>> >>> E.g. does a >>> $ dd if=3D/dev/zero bs=3D1M | hexdump -C=20 >>> have the same issue? >>> >> >> I think there might be a chance that the above executes correctly, eve= n >> if we have memory corruption -- this might be e.g. because the actual >> "dest" buffer here would be much smaller than the fs cache buffer used= >> when we copy onto disk. And so our small dest buffer might just not be= >> so likely to be hit with this presumably random corruption. >> >> Perhaps dd'ing onto /dev/shm would be a better way to check this? >=20 > I agree that a negative doesn't mean much. I'm just poking around there= > because the positive would have mattered: If we still get to see it, > we're out of the storage discussion and can focus on memory corruption.= >=20 If you're thinking about a potential Dom0 disk-driver problem, then I think we can rule this out. This is because I have tried this on both encrypted and non-encrypted filesystems, but the pattern of corruptions was exactly the same. If the disk driver was feeding LUKS (the crypto driver) with a wrong data, the corruptions would definitely look differently. I also tried ext4 and ext3 filesystems, but same results. j. --------------enig133F0ED8EB7A105BAF520697 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iEYEARECAAYFAkuVjqcACgkQORdkotfEW84cWACeMLx/bT6yKMlTSLVmHCWQ4135 SaEAnRyb2jsuw7vCtcivPgekEkRSIZT+ =RDGn -----END PGP SIGNATURE----- --------------enig133F0ED8EB7A105BAF520697-- --===============0698778330== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel --===============0698778330==--