linux-kernel - Re: [PATCH] random: opportunistically initialize on /dev/urandom reads

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Date:   Tue, 5 Apr 2022 11:56:33 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>
Subject: Re: [PATCH] random: opportunistically initialize on /dev/urandom reads

On Tue, Apr 5, 2022 at 11:31 AM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> It sounds like your suggestion would be to make that:
>
>   while (!crng_ready()) {
>     int ret;
>
>     try_to_generate_entropy();
>     if (nodelay && !crng_ready()) {
>       warn(...);
>       return -EBUSY;
>     }
>     ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
>     if (ret)
>       return ret > 0 ? 0 : ret;
>   }

Yes. Except I'd almost warn for the "ret < 0" case too, since almost
nobody seems to check it.

But hey, maybe callers that are interrupted by a signal check for that
separately. I guess it's _possible_.

             Linus