linux-kernel - Re: [PATCH v2 1/2] hwrng: fetch randomness only after device init

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Message-ID: <20140709131737.GO13433@titan.lakedaemon.net>
Date:	Wed, 9 Jul 2014 09:17:37 -0400
From:	Jason Cooper <jason@...edaemon.net>
To:	Amit Shah <amit.shah@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Virtualization List <virtualization@...ts.linux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	herbert@...dor.apana.org.au, keescook@...omium.org,
	stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] hwrng: fetch randomness only after device init

On Wed, Jul 09, 2014 at 06:38:22PM +0530, Amit Shah wrote:
> On (Wed) 09 Jul 2014 [07:53:17], Jason Cooper wrote:
> > On Sat, Jul 05, 2014 at 11:04:52AM +0530, Amit Shah wrote:
> > > Commit d9e7972619334 "hwrng: add randomness to system from rng sources"
> > > added a call to rng_get_data() from the hwrng_register() function.
> > > However, some rng devices need initialization before data can be read
> > > from them.
> > > 
> > > This commit makes the call to rng_get_data() depend on no init fn
> > > pointer being registered by the device.  If an init function is
> > > registered, this call is made after device init.
> > > 
> > > CC: Kees Cook <keescook@...omium.org>
> > > CC: Jason Cooper <jason@...edaemon.net>
> > > CC: Herbert Xu <herbert@...dor.apana.org.au>
> > > CC: <stable@...r.kernel.org> # For v3.15+
> > > Signed-off-by: Amit Shah <amit.shah@...hat.com>
> > > ---
> > >  drivers/char/hw_random/core.c | 31 +++++++++++++++++++++++++------
> > >  1 file changed, 25 insertions(+), 6 deletions(-)
> > 
> > Thanks for cleaning this up!
> 
> Thanks!
> 
> Any thoughts on the follow-up patch posted later that resolves some of
> the weirdness in init?

hmm, I'd rather see an init function for virtio-rng that checks the bit
and returns 0 or -EAGAIN.  With your proposed change, you would get
hangs again.

thx,

Jason.
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