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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 B394FC4CECD for ; Tue, 17 Sep 2019 21:52:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 81FE22171F for ; Tue, 17 Sep 2019 21:52:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=codon.org.uk header.i=@codon.org.uk header.b="DwTJNUQ8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727131AbfIQVwY (ORCPT ); Tue, 17 Sep 2019 17:52:24 -0400 Received: from cavan.codon.org.uk ([93.93.128.6]:58550 "EHLO cavan.codon.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726902AbfIQVwY (ORCPT ); Tue, 17 Sep 2019 17:52:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=codon.org.uk; s=63138784; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ca4Lhweyqz92nJyY4L52arK98MpJ203Gl7QAiPb4ap0=; b=DwTJNUQ8yCEtLTkhaV9aHyfbMN O3iKbXNzLDBx8o+KQ5sXbLOi7HA7oif5rLNCgaIu0GA7Ml7qLArYCHiD3MI3Yf1jJ8meJdBPQzkCP sooXvUeDqQAHpNlgBE+K8QU5hMqaYVrJQ7boqm7hSTTAV8cirKS+1NdYEH1KYj1EXpsA=; Received: from mjg59 by cavan.codon.org.uk with local (Exim 4.89) (envelope-from ) id 1iALOC-0006gx-Us; Tue, 17 Sep 2019 22:52:00 +0100 Date: Tue, 17 Sep 2019 22:52:00 +0100 From: Matthew Garrett To: Martin Steigerwald Cc: "Ahmed S. Darwish" , Linus Torvalds , Lennart Poettering , "Theodore Y. Ts'o" , Willy Tarreau , Vito Caputo , Andreas Dilger , Jan Kara , Ray Strode , William Jon McCann , "Alexander E. Patrakov" , zhangjs , linux-ext4@vger.kernel.org, lkml Subject: Re: Linux 5.3-rc8 Message-ID: <20190917215200.wtjim3t6zgt7gdmw@srcf.ucam.org> References: <2658007.Cequ2ms4lF@merkaba> <20190917205234.GA1765@darwi-home-pc> <1722575.Y5XjozQscI@merkaba> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1722575.Y5XjozQscI@merkaba> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: mjg59@cavan.codon.org.uk X-SA-Exim-Scanned: No (on cavan.codon.org.uk); SAEximRunCond expanded to false Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Archived-At: List-Archive: List-Post: On Tue, Sep 17, 2019 at 11:38:33PM +0200, Martin Steigerwald wrote: > My understanding of entropy always has been that only a certain amount > of it can be produced in a certain amount of time. If that is wrong… > please by all means, please teach me, how it would be. getrandom() will never "consume entropy" in a way that will block any users of getrandom(). If you don't have enough collected entropy to seed the rng, getrandom() will block. If you do, getrandom() will generate as many numbers as you ask it to, even if no more entropy is ever collected by the system. So it doesn't matter how many clients you have calling getrandom() in the boot process - either there'll be enough entropy available to satisfy all of them, or there'll be too little to satisfy any of them. -- Matthew Garrett | mjg59@srcf.ucam.org