linux-kernel - Re: [PATCH 3/8] random: trigger random_ready callback upon crng

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Message-ID: <20170118041250.x7wszcasd4dplj3h@thunk.org>
Date:   Tue, 17 Jan 2017 23:12:50 -0500
From:   Theodore Ts'o <tytso@....edu>
To:     Stephan Müller <smueller@...onox.de>
Cc:     linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH 3/8] random: trigger random_ready callback upon crng_init
 == 1

On Tue, Dec 27, 2016 at 11:39:57PM +0100, Stephan Müller wrote:
> The random_ready callback mechanism is intended to replicate the
> getrandom system call behavior to in-kernel users. As the getrandom
> system call unblocks with crng_init == 1, trigger the random_ready
> wakeup call at the same time.

It was deliberate that random_ready would only get triggered with
crng_init==2.

In general I'm assuming kernel callers really want real randomness (as
opposed to using prandom), where as there's a lot of b.s. userspace
users of kernel randomness (for things that really don't require
cryptographic randomness, e.g., for salting Python dictionaries,
systemd/udev using /dev/urandom for non-cryptographic, non-security
applications etc.)

						- Ted