From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.7 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 37AC47D90D for ; Fri, 16 Aug 2019 09:07:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726842AbfHPJHS (ORCPT ); Fri, 16 Aug 2019 05:07:18 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:39959 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726800AbfHPJHS (ORCPT ); Fri, 16 Aug 2019 05:07:18 -0400 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 512) id D68E380F3A; Fri, 16 Aug 2019 11:07:01 +0200 (CEST) Date: Fri, 16 Aug 2019 11:07:13 +0200 From: Pavel Machek To: "Theodore Y. Ts'o" , "Lendacky, Thomas" , nhorman@tuxdriver.com, "linux-kernel@vger.kernel.org" , "linux-doc@vger.kernel.org" , "linux-pm@vger.kernel.org" , "x86@kernel.org" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "Rafael J . Wysocki" , Chen Yu , Jonathan Corbet Subject: Re: Non-random RDRAND Re: [PATCH] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h Message-ID: <20190816090713.GA17833@amd> References: <776cb5c2d33e7fd0d2893904724c0e52b394f24a.1565817448.git.thomas.lendacky@amd.com> <20190814232434.GA31769@amd> <20190815151224.GB18727@mit.edu> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="vtzGhvizbBRQ85DL" Content-Disposition: inline In-Reply-To: <20190815151224.GB18727@mit.edu> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org --vtzGhvizbBRQ85DL Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu 2019-08-15 11:12:24, Theodore Y. Ts'o wrote: > On Thu, Aug 15, 2019 at 01:24:35AM +0200, Pavel Machek wrote: > > Burn it with fire! > >=20 > > I mean... people were afraid RDRAND would be backdoored, and you now > > confirm ... it indeed _is_ backdoored? /., here's news for you! >=20 > To be fair to AMD, I wouldn't call it a backdoor. Hanlon's razor is > applicable here: >=20 > "Never attribute to malice that which can be adequately > explained by neglect." > (Sometimes other words are used instead of neglect, but i'm trying to > be nice.) You are right, I thought it was returning values with low entropy, and it returns ~0 (so -- really really low entropy :-) and can't be clasified as a backdoor. Anyway, AMD is _not_ doing good job right now. I'd expect: a) CVE reference b) real fix; if BIOS can init the rng, so can kernel Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --vtzGhvizbBRQ85DL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl1WckEACgkQMOfwapXb+vJUmgCbBaZAQvUTMEhu0sVBHUxqvAVR ZPEAn3mz1LDei9CmYiqspf9+V/tvyKCj =tgYd -----END PGP SIGNATURE----- --vtzGhvizbBRQ85DL--