linux-kernel - Re: [PATCH v3 05/13] security/keys: ensure RNG is seeded before use

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Date:   Tue, 6 Jun 2017 14:23:09 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     David Howells <dhowells@...hat.com>
Cc:     "Theodore Ts'o" <tytso@....edu>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Miller <davem@...emloft.net>,
        Mimi Zohar <zohar@...ux.vnet.ibm.com>,
        David Safford <safford@...ibm.com>
Subject: Re: [PATCH v3 05/13] security/keys: ensure RNG is seeded before use

On Tue, Jun 6, 2017 at 12:08 PM, David Howells <dhowells@...hat.com> wrote:
> Jason A. Donenfeld <Jason@...c4.com> wrote:
>
>> +             key->serial = get_random_u32() >> 1;
>
> If this may sleep, it must be interruptible.

That won't sleep. I could have made it get_random_u32_wait(), but we'd
get into trouble at boottime. So instead, for now, I just use
get_random_u32 rather than get_random_bytes, which can use the
architectural random number generator, when the platform has one,
which is available early on.