From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34301) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XIHJi-0003M3-QP for qemu-devel@nongnu.org; Fri, 15 Aug 2014 09:13:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XIHJd-0006sS-Tf for qemu-devel@nongnu.org; Fri, 15 Aug 2014 09:13:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55871) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XIHJd-0006sL-Kw for qemu-devel@nongnu.org; Fri, 15 Aug 2014 09:13:09 -0400 Message-ID: <53EE0763.2040400@redhat.com> Date: Fri, 15 Aug 2014 07:13:07 -0600 From: Eric Blake MIME-Version: 1.0 References: <1406900401-19550-1-git-send-email-lkurusa@redhat.com> <20140812132034.GM20490@stefanha-thinkpad.redhat.com> <20140812133542.GA6876@localhost.localdomain> <1643597569.19303034.1408027347194.JavaMail.zimbra@redhat.com> <20140814145733.GA2399@localhost.localdomain> <20140815105519.GC3770@noname.redhat.com> <87ioluhuc0.fsf@blackfin.pond.sub.org> <20140815122839.GC2399@localhost.localdomain> In-Reply-To: <20140815122839.GC2399@localhost.localdomain> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="aWQWS8Q3Gbp5UEtUT6HjSI4OgQlHsoi2K" Subject: Re: [Qemu-devel] [PATCH 0/3] vpc: support probing of fixed size images List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody , Markus Armbruster Cc: Kevin Wolf , Levente Kurusa , Fam Zheng , Stefan Weil , Andrew Jones , QEMU Developers , Stefan Hajnoczi This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --aWQWS8Q3Gbp5UEtUT6HjSI4OgQlHsoi2K Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 08/15/2014 06:28 AM, Jeff Cody wrote: > I worry that will subtly alter current behavior in bad ways. For > instance, take this image chain: >=20 > qemu-img create -f qcow2 foo.img 1G > qemu-img create -f qcow2 -b foo.img bar.img 1G >=20 > qemu-kvm -drive file=3Dbar.img,format=3Dqcow2 >=20 >=20 > If I understand correctly what you are proposing, that means that > qemu-kvm would detect 'foo.img' as raw, while current behavior is to > detect it as 'qcow2'. >=20 Libvirt ALREADY defaults to detecting foo.img as raw, and refuses to grant SELinux permissions for qemu to read bar.img, which causes qemu to fail to start due to missing permissions. All because probing is deemed too dangerous (a probe that results in an answer of "raw" is trustworthy, a probe that results in any other answer is suspect if the file has any remote chance of having once been raw). > Although if we do that in conjunction with what Kevin proposed (forbid > probing on raw), it would behave 'properly', and bail out before doing > something bad. That could be OK. The problem is that you can't forbid probing on raw without forbidding probing almost everywhere. Again, an answer of "raw" is trustworthy, it is ALL OTHER answers that are suspect. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --aWQWS8Q3Gbp5UEtUT6HjSI4OgQlHsoi2K Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg iQEcBAEBCAAGBQJT7gdjAAoJEKeha0olJ0NqioYIAI0az2IfDYP2L6jlWyYuDhzb l68mT3/8SIGPyJVHWajadWre1gpNp+CKkQTEwjQ0hbeQ2rCFTf6JsAFytoaT96Li 5nrDm5C328weJgUgmewleOnlnHwh57BQLhv9KfVTl4twc/UAHmqeN1lfsCvdq0E1 Npb/2+J0Ms3GsgNZwk4zVz2yllqjtqV9q6A7PfonbL8HfjyK00g7FuueQPr8cUrf Do1zBE9pCmF2Ct0ToKaogjYaIWK6HPEFf+JvEGgFq6ESj9G/yhtjtJX2SwXg8iAK wbBtN5uI7B/8L4ufmdVv8D3YBvNVeNiCmmEV32gR5MVJ0ww66q1eHJsoneSF6XQ= =MgQr -----END PGP SIGNATURE----- --aWQWS8Q3Gbp5UEtUT6HjSI4OgQlHsoi2K--