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

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Date:   Mon, 18 Jul 2022 14:20:37 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>, stable@...r.kernel.org,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v4 RESEND] timekeeping: contribute wall clock to rng on
 time change

On Sun, Jul 17 2022 at 23:53, 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
> Reviewed-by: Eric Biggers <ebiggers@...gle.com>
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>