linux-kernel - Re: [PATCH] init: call time_init() before rand

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YnbgAGgC0DFBvLcL@zx2c4.com>
Date:   Sat, 7 May 2022 23:09:20 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Stafford Horne <shorne@...il.com>
Subject: Re: [PATCH] init: call time_init() before rand_initialize()

Hi Andrew,

On Sat, May 07, 2022 at 12:26:53PM -0700, Andrew Morton wrote:
> On Thu,  5 May 2022 02:31:14 +0200 "Jason A. Donenfeld" <Jason@...c4.com> wrote:
> 
> > Currently time_init() is called before rand_initialize(), but
> 
> You mean "after"!  Changelog was really confusing until I went and
> looked at the code.

Oh dear, yes. Will fix that.

> 
> > rand_initialize() makes use of the timer on various platforms, and
> > sometimes this timer needs to be initialized by time_init() first. In
> > order to not return zero, 
> 
> return zero from what?

random_get_entropy_fallback(). I'll fix that in the commit message.

> > reverse the order of these two calls. The
> > block doing random initialization was right before time_init() before,
> > so changing the order shouldn't have any complicated effects.
> 
> I hope you're right.  Moving these things around tends to fix one thing
> and break another.

I hope so too. Reading the platform code for every arch I can't see
where breakage would be. Nothing in the time init functions relies on
the rng being available, and actually, the rng is already quasi
functional before the call to rand_initialize(), so I think it should be
good. Nonetheless:

> No probs.  Plenty of testing in linux-next, please.

Exactly this. Plus the CI on build.wireguard.com and such is churning on
it on a variety of different archs.

Jason