From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753587AbaC0GCZ (ORCPT ); Thu, 27 Mar 2014 02:02:25 -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 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: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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 --- 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; -- 1.8.3.2