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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 84604C43382 for ; Wed, 26 Sep 2018 10:35:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 47E3B20842 for ; Wed, 26 Sep 2018 10:35:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 47E3B20842 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727588AbeIZQrp (ORCPT ); Wed, 26 Sep 2018 12:47:45 -0400 Received: from mga12.intel.com ([192.55.52.136]:20160 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726915AbeIZQrp (ORCPT ); Wed, 26 Sep 2018 12:47:45 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Sep 2018 03:35:26 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,306,1534834800"; d="scan'208";a="76312337" Received: from imahmed1-mobl2.ger.corp.intel.com (HELO localhost) ([10.252.50.69]) by orsmga008.jf.intel.com with ESMTP; 26 Sep 2018 03:35:23 -0700 Date: Wed, 26 Sep 2018 13:35:21 +0300 From: Jarkko Sakkinen To: Louis Collard Cc: linux-integrity@vger.kernel.org, Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, apronin@chromium.org, Jason Gunthorpe , david.bild@xaptum.com Subject: Re: [PATCH] Allow hwrng to initialize crng. Message-ID: <20180926103521.GB4885@linux.intel.com> References: <20180926032455.224600-1-louiscollard@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180926032455.224600-1-louiscollard@chromium.org> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 26, 2018 at 11:24:55AM +0800, Louis Collard wrote: > Some systems, for example embedded systems, do not generate > enough entropy on boot through interrupts, and boot may be blocked for > several minutes waiting for a call to getrandom to complete. > > Currently, random data is read from a hwrng when it is registered, > and is loaded into primary_crng. This data is treated in the same > way as data that is device-specific but otherwise unchanging, and > so primary_crng cannot become initialized with the data from the > hwrng. > > This change causes the data initially read from the hwrng to be > treated the same as subsequent data that is read from the hwrng if > it's quality score is non-zero. > > The implications of this are: > > The data read from hwrng can cause primary_crng to become > initialized, therefore avoiding problems of getrandom blocking > on boot. > > Calls to getrandom (with GRND_RANDOM) may be using entropy > exclusively (or in practise, almost exclusively) from the hwrng. > > Regarding the latter point; this behavior is the same as if a > user specified a quality score of 1 (bit of entropy per 1024 bits) > so hopefully this is not too scary a change to make. > > This change is the result of the discussion here: > https://patchwork.kernel.org/patch/10453893/ > > Signed-off-by: Louis Collard Acked-by: Jarkko Sakkinen /Jarkko