From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756520AbaCZXku (ORCPT ); Wed, 26 Mar 2014 19:40:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65474 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752126AbaCZXkt (ORCPT ); Wed, 26 Mar 2014 19:40:49 -0400 Message-ID: <53336576.1090503@redhat.com> Date: Thu, 27 Mar 2014 00:40:38 +0100 From: Daniel Borkmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Sasha Levin CC: davem@davemloft.net, hannes@stressinduktion.org, tytso@mit.edu, linux-kernel@vger.kernel.org, eric.dumazet@gmail.com Subject: Re: [PATCH] random32: avoid attempt to late reseed if in the middle of seeding References: <1395853958-5083-1-git-send-email-sasha.levin@oracle.com> <53336049.4060901@redhat.com> <53336425.6030409@oracle.com> In-Reply-To: <53336425.6030409@oracle.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/27/2014 12:35 AM, Sasha Levin wrote: > On 03/26/2014 07:18 PM, Daniel Borkmann wrote: >> On 03/26/2014 06:12 PM, Sasha Levin wrote: >>> Commit 4af712e8df ("random32: add prandom_reseed_late() and call when >>> nonblocking pool becomes initialized") has added a late reseed stage >>> that happens as soon as the nonblocking pool is marked as initialized. >>> >>> This fails in the case that the nonblocking pool gets initialized >>> during __prandom_reseed()'s call to get_random_bytes(). In that case >>> we'd double back into __prandom_reseed() in an attempt to do a late >>> reseed - deadlocking on 'lock' early on in the boot process. >>> >>> Instead, just avoid even waiting to do a reseed if a reseed is already >>> occuring. >>> >>> Signed-off-by: Sasha Levin >> >> Thanks for catching! (If you want Dave to pick it up, please also >> Cc netdev.) >> >> Why not via spin_trylock_irqsave() ? Thus, if we already hold the >> lock, we do not bother any longer with doing the same work twice >> and just return. > > Your code looks much better, I'll should really stop sending patches > too early in the morning... > > It's also worth adding lib/random32.c to the MAINTAINERS file, as my > list of recipients is solely based on what get_maintainer.pl tells > me to do (and I'm assuming that I'm not the last person who will be > sending patches for this). Sounds like a good idea, afaik, historically, this got ripped out as a lib from networking subsystem. That's why we've sent it to netdev last time. Cheers, Daniel