linux-kernel - Re: [PATCH v2 2/9] random: get rid of secondary crngs

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Message-ID: <YgN5wp58XHYd7/WA@owl.dominikbrodowski.net>
Date:   Wed, 9 Feb 2022 09:22:26 +0100
From:   Dominik Brodowski <linux@...inikbrodowski.net>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        tytso@....edu, ebiggers@...nel.org
Subject: Re: [PATCH v2 2/9] random: get rid of secondary crngs

Just one question (which was already present in the past, but...):

> -	WRITE_ONCE(crng->init_time, jiffies);
> -	spin_unlock_irqrestore(&crng->lock, flags);
> -	if (crng == &primary_crng && crng_init < 2)
> -		crng_finalize_init();
> +	WRITE_ONCE(primary_crng.init_time, jiffies);
> +	spin_unlock_irqrestore(&primary_crng.lock, flags);
> +	if (crng_init < 2) {
> +		invalidate_batched_entropy();
> +		crng_init = 2;

Might this branch be taken twice if crng_reseed() is called concurrently
twice? If so, we'd need to increment crng_init while holding the lock,
such as I suggested in my patch "random: fix locking for crng_init in
crng_reseed()". But that can be deferred to an additional patch.

Thanks,
	Dominik