linux-kernel - Re: [PATCH v4] timekeeping: contribute wall clock to rng on time change

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Message-ID: <Yr2f13QhFsyxdDS7@zx2c4.com>
Date:   Thu, 30 Jun 2022 15:06:31 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     tglx@...utronix.de
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        stable@...r.kernel.org, ebiggers@...nel.org
Subject: Re: [PATCH v4] timekeeping: contribute wall clock to rng on time
 change

Hi Thomas,

On Thu, Jun 23, 2022 at 12:36:23PM -0700, Eric Biggers wrote:
> On Thu, Jun 23, 2022 at 09:12:49PM +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@...r.kernel.org
> > Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> > ---
> >  kernel/time/timekeeping.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> Reviewed-by: Eric Biggers <ebiggers@...gle.com>

Thought I should bump this patch in case you missed it.

Jason