Skip site navigation (1)Skip section navigation (2)
Date:      Fri, 20 Jan 2012 09:58:23 +0400
From:      Andrey Chernov <ache@FreeBSD.ORG>
To:        Mark Murray <markm@FreeBSD.ORG>
Cc:        svn-src-head@FreeBSD.ORG, David Schultz <das@FreeBSD.ORG>, src-committers@FreeBSD.ORG, svn-src-all@FreeBSD.ORG
Subject:   Re: svn commit: r230230 - head/sys/dev/random
Message-ID:  <20120120055823.GA28177@vniz.net>
In-Reply-To: <E1Rny2A-000C3x-O6@groundzero.grondar.org>
References:  <201201162018.q0GKIADK050161@svn.freebsd.org> <20120118061943.GA80874@vniz.net> <E1Rny2A-000C3x-O6@groundzero.grondar.org>

next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Jan 19, 2012 at 07:52:30PM +0000, Mark Murray wrote:
> Andrey Chernov writes:
> > On Mon, Jan 16, 2012 at 08:18:10PM +0000, David Schultz wrote:
> > > Author: das
> > > Date: Mon Jan 16 20:18:10 2012
> > > New Revision: 230230
> > > URL: http://svn.freebsd.org/changeset/base/230230
> > > 
> > > Log:
> > >   Generate a warning if the kernel's arc4random() is seeded with bogus entropy.
> > 
> > While you are here, could you review/commit my patch to fix bad 31bit
> > arc4rand() seeding, please?
> > 
> > --- yarrow.c.bak	2011-09-26 07:35:48.000000000 +0400
> > +++ yarrow.c	2012-01-18 10:13:47.000000000 +0400
> 
> This is the wrong place for this; it may achieve the desired result, but
> the file is where the Yarrow algorithm is implepeneted; ARC4 reseeds are
> not a part of that, which makes this proposal a layering violation at
> best, and an unwarranted dependancy at worst.
> 
> Look at the function random_yarrow_unblock(). Thats where yopu want to
> be doing this. This function is where the random device is unblocked
> once safely seeded.

Thanx for your hint, but I fear one moment using random_yarrow_unblock().
It is called under mtx_lock(&random_reseed_mtx) in reseed().
And when arc4rand() seeding is called, it uses read_random(), so I see 
possible deadlock can happens.
In my version arc4rand() seeding happens only when this lock is released,
so no blocking is possible. 
But perhaps I oversight something, correct me if I am wrong, please.

-- 
http://ache.vniz.net/



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20120120055823.GA28177>