From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756492AbaCZXfO (ORCPT ); Wed, 26 Mar 2014 19:35:14 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:41555 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755288AbaCZXfM (ORCPT ); Wed, 26 Mar 2014 19:35:12 -0400 Message-ID: <53336425.6030409@oracle.com> Date: Wed, 26 Mar 2014 19:35:01 -0400 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Daniel Borkmann 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> In-Reply-To: <53336049.4060901@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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). Thanks, Sasha