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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7659C433EF for ; Thu, 23 Jun 2022 19:27:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231240AbiFWT1q (ORCPT ); Thu, 23 Jun 2022 15:27:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231510AbiFWT1Z (ORCPT ); Thu, 23 Jun 2022 15:27:25 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2987F20BD3; Thu, 23 Jun 2022 11:53:05 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 03D6F6202D; Thu, 23 Jun 2022 18:53:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2738C341C6; Thu, 23 Jun 2022 18:53:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1656010384; bh=uKIRvyg7pjGx9VZRIlqn21I3/K3/JUHP9hWujvj8T8A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RL6a3wqo7WvdfrWlenL1jjEYetWhAUljOhKZV4Q1henzewDVuCy4RV+NlbhSV8tZV KCvxk/i/UJO52K7vr0qcqTp5t/EKESrPPyulJIRhR4cNevq7ozSrTyebtOEN1uOXjc Y8UqDOqcuKfVKlqV4Xu4dmRzn822z0ghDT3FvmORkcXad1H71/YeFrDH2ODP2Qv3wV 7gH7EmnVQwWWEfQvFKx/NJbFsfTEgxI1i3+NtkVqorlbAN8HI1ObqEQByihSOk1z8A wpg+xT/HDmAGHH951uvRe/RJTPLI7ywlpILAOeMZTAfg4x1vRzHlI/PgesB/OAlNYx t8GU0r1FeBGag== Date: Thu, 23 Jun 2022 11:53:02 -0700 From: Eric Biggers To: "Jason A. Donenfeld" Cc: LKML , Thomas Gleixner , Linux Crypto Mailing List , stable@vger.kernel.org Subject: Re: [PATCH v2] timekeeping: contribute wall clock to rng on time change Message-ID: References: <20220623180555.1345684-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220623180555.1345684-1-Jason@zx2c4.com> Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Thu, Jun 23, 2022 at 08:05:55PM +0200, Jason A. Donenfeld wrote: > The rng's random_init() function contributes the real time to the rng at > boot time, so that events can at least start in relation to something > particular in the real world. But this clock might not yet be set that > point in boot, so nothing is contributed. In addition, the relation > between minor clock changes from, say, NTP, and the cycle counter is > potentially useful entropic data. > > This commit addresses this by mixing in a time stamp on calls to > settimeofday and adjtimex. No entropy is credited in doing so, so it > doesn't make initialization faster, but it is still useful input to > have. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: stable@vger.kernel.org > Signed-off-by: Jason A. Donenfeld > --- > kernel/time/timekeeping.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c > index 8e4b3c32fcf9..89b894b3ede8 100644 > --- a/kernel/time/timekeeping.c > +++ b/kernel/time/timekeeping.c > @@ -23,6 +23,7 @@ > #include > #include > #include > +#include > > #include "tick-internal.h" > #include "ntp_internal.h" > @@ -1331,6 +1332,8 @@ int do_settimeofday64(const struct timespec64 *ts) > goto out; > } > > + add_device_randomness(&ts, sizeof(ts)); > + > tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta)); This is now nested inside: raw_spin_lock_irqsave(&timekeeper_lock, flags); write_seqcount_begin(&tk_core.seq); Could there be a deadlock if random_get_entropy() in add_device_randomness() falls back to reading the monotonic clock? - Eric