From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 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 In-Reply-To: <20180926032455.224600-1-louiscollard@chromium.org> Sender: linux-integrity-owner@vger.kernel.org List-ID: 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