From patchwork Thu Mar 27 06:01:35 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sasha Levin X-Patchwork-Id: 334223 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 7CF4414008B for ; Thu, 27 Mar 2014 17:03:35 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753468AbaC0GCY (ORCPT ); Thu, 27 Mar 2014 02:02:24 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:44644 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbaC0GCB (ORCPT ); Thu, 27 Mar 2014 02:02:01 -0400 Received: from acsinet21.oracle.com (acsinet21.oracle.com [141.146.126.237]) by userp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id s2R61qbq008995 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 27 Mar 2014 06:01:53 GMT Received: from aserz7022.oracle.com (aserz7022.oracle.com [141.146.126.231]) by acsinet21.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id s2R61qrw019715 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 27 Mar 2014 06:01:52 GMT Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by aserz7022.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id s2R61qDd015682; Thu, 27 Mar 2014 06:01:52 GMT Received: from lappy.msi.event (/10.159.165.196) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 26 Mar 2014 23:01:51 -0700 From: Sasha Levin To: davem@davemloft.net Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, hannes@stressinduktion.org, tytso@mit.edu, dborkman@redhat.com, Sasha Levin Subject: [PATCH v2] random32: avoid attempt to late reseed if in the middle of seeding Date: Thu, 27 Mar 2014 02:01:35 -0400 Message-Id: <1395900095-15254-2-git-send-email-sasha.levin@oracle.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1395900095-15254-1-git-send-email-sasha.levin@oracle.com> References: <1395900095-15254-1-git-send-email-sasha.levin@oracle.com> X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 Acked-by: Hannes Frederic Sowa Acked-by: Daniel Borkmann --- lib/random32.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/lib/random32.c b/lib/random32.c index b33b23e..d67b6a7 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -245,8 +245,20 @@ static void __prandom_reseed(bool late) static bool latch = false; static DEFINE_SPINLOCK(lock); + /* + * Asking for random bytes might result in bytes getting + * moved into the nonblocking pool and thus marking it + * as initialized. In this case we would double back into + * this function and attempt to do a late reseed. + * Ignore the pointless attempt to reseed again if we're + * already waiting for bytes when the nonblocking pool + * got initialized. + */ + /* only allow initial seeding (late == false) once */ - spin_lock_irqsave(&lock, flags); + if (!spin_trylock_irqsave(&lock, flags)) + return; + if (latch && !late) goto out;