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 C8A68C2D0DB for ; Sun, 26 Jan 2020 21:26:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9215C206F0 for ; Sun, 26 Jan 2020 21:26:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727141AbgAZV02 (ORCPT ); Sun, 26 Jan 2020 16:26:28 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:60797 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726144AbgAZV02 (ORCPT ); Sun, 26 Jan 2020 16:26:28 -0500 Received: from callcc.thunk.org (rrcs-67-53-201-206.west.biz.rr.com [67.53.201.206]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 00QLQKr6014139 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 26 Jan 2020 16:26:23 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id E98FE420324; Sun, 26 Jan 2020 16:26:19 -0500 (EST) Date: Sun, 26 Jan 2020 16:26:19 -0500 From: "Theodore Y. Ts'o" To: Toralf =?iso-8859-1?Q?F=F6rster?= Cc: Linux Kernel Subject: Re: delayed "random: get_random_bytes" line in dmesg Message-ID: <20200126212619.GA13716@mit.edu> References: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 26, 2020 at 03:41:24PM +0100, Toralf Förster wrote: > I do wonder a little bit about the timestamp of the "random: get_random_bytes" near the end b/c it is way delayed, or? The get_random_bytes call in setup_net is used to initialize value returned by net_hash_mix() for the root net namespace. So if that's not super random, an attacker might be able to use that to leverage kernel level attacks. It's at least not being used for a cryptographic purpose, though. > Linux mr-fox 5.4.15 #6 SMP Sun Jan 26 10:07:17 CET 2020 x86_64 Intel(R) Xeon(R) CPU E5-1650 v3 @ 3.50GHz GenuineIntel GNU/Linux The E5-1650 is a (roughly) eight year old chip with the Sandy Bridge architecture, and that was the last architecture _not_ to support RDRAND. - Ted