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=-3.8 required=3.0 tests=BAYES_00,FAKE_REPLY_C, 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 E17D5C43461 for ; Thu, 17 Sep 2020 08:11:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0122221E3 for ; Thu, 17 Sep 2020 08:11:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726403AbgIQILO (ORCPT ); Thu, 17 Sep 2020 04:11:14 -0400 Received: from helcar.hmeau.com ([216.24.177.18]:54830 "EHLO fornost.hmeau.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726444AbgIQIK5 (ORCPT ); Thu, 17 Sep 2020 04:10:57 -0400 X-Greylist: delayed 2637 seconds by postgrey-1.27 at vger.kernel.org; Thu, 17 Sep 2020 04:10:55 EDT Received: from gwarestrin.arnor.me.apana.org.au ([192.168.0.7]) by fornost.hmeau.com with smtp (Exim 4.92 #5 (Debian)) id 1kIoJY-0004gr-B0; Thu, 17 Sep 2020 17:26:45 +1000 Received: by gwarestrin.arnor.me.apana.org.au (sSMTP sendmail emulation); Thu, 17 Sep 2020 17:26:44 +1000 Date: Thu, 17 Sep 2020 17:26:44 +1000 From: Herbert Xu To: Eric Biggers Cc: tytso@mit.edu, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] random: use correct memory barriers for crng_node_pool Message-ID: <20200917072644.GA5311@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200916233042.51634-1-ebiggers@kernel.org> X-Newsgroups: apana.lists.os.linux.cryptoapi,apana.lists.os.linux.kernel User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Eric Biggers wrote: > From: Eric Biggers > > When a CPU selects which CRNG to use, it accesses crng_node_pool without > a memory barrier. That's wrong, because crng_node_pool can be set by > another CPU concurrently. Without a memory barrier, the crng_state that > is used might not appear to be fully initialized. The only architecture that requires a barrier for data dependency is Alpha. The correct primitive to ensure that barrier is present is smp_barrier_depends, or you could just use READ_ONCE. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt