From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7CDD8C43331 for ; Sun, 29 Mar 2020 12:21:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 567C92076A for ; Sun, 29 Mar 2020 12:21:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728143AbgC2MVv convert rfc822-to-8bit (ORCPT ); Sun, 29 Mar 2020 08:21:51 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:33084 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728044AbgC2MVv (ORCPT ); Sun, 29 Mar 2020 08:21:51 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-135-E2d1cB3MNcKiBN6SYycyaw-1; Sun, 29 Mar 2020 13:21:47 +0100 X-MC-Unique: E2d1cB3MNcKiBN6SYycyaw-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Sun, 29 Mar 2020 13:21:47 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Sun, 29 Mar 2020 13:21:47 +0100 From: David Laight To: 'George Spelvin' , Dan Williams CC: Linux Kernel Mailing List , Qian Cai , Kees Cook , Michal Hocko , Andrew Morton , Linux MM Subject: RE: [RFC PATCH v1 00/52] Audit kernel random number use Thread-Topic: [RFC PATCH v1 00/52] Audit kernel random number use Thread-Index: AQHWBS7wHKwkXcotX0GE2ObBbkw++6hffddg Date: Sun, 29 Mar 2020 12:21:46 +0000 Message-ID: <98bd30f23b374ccbb61dd46125dc9669@AcuMS.aculab.com> References: <202003281643.02SGhPmY017434@sdf.org> <20200328182817.GE5859@SDF.ORG> In-Reply-To: <20200328182817.GE5859@SDF.ORG> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: George Spelvin > Sent: 28 March 2020 18:28 ... > 20..23: Changes to the prandom_u32() generator itself. Including > switching to a stronger & faster PRNG. Does this remove the code that used 'xor' to combine the output of (about) 5 LFSR? Or is that somewhere else? I didn't spot it in the patches - so it might already have gone. Using xor was particularly stupid. The whole generator was then linear and trivially reversable. Just using addition would have made it much stronger. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)