linux-kernel - Re: [PATCH] random: re-add removed comment about get_random

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Date:   Wed, 23 Mar 2022 20:24:49 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] random: re-add removed comment about
 get_random_{u32,u64} reseeding

Am Tue, Mar 22, 2022 at 10:23:36PM -0600 schrieb Jason A. Donenfeld:
> The comment about get_random_{u32,u64}() not invoking reseeding got
> added in an unrelated commit, that then was recently reverted. So this
> adds that little comment snippet back.
> 
> Cc: Dominik Brodowski <linux@...inikbrodowski.net>
> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
> ---
>  drivers/char/random.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index 1d7aac2a9600..82e37d7dd9f1 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -226,7 +226,7 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller, void
>   * into the given buffer or as a return value. This is equivalent to
>   * a read from /dev/urandom. The integer family of functions may be
>   * higher performance for one-off random integers, because they do a
> - * bit of buffering.
> + * bit of buffering and do not invoke reseeding.
>   *
>   *********************************************************************/

Actually, that seems wrong, as all these functions may call
_get_random_bytes(), which may invoke crng_make_state(), which
may invoke crng_reseed(). And it might be worthwhile to clarify
that it's only get_random_bytes() that does not do the bit of
buffering.

Thanks,
	Dominik