linux-kernel - Re: Commit d9e7972619334656 breaks KVM's virtio-rng-pci

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Message-ID: <CAGXu5jK6XzrMg_VPYm9LhBjmRHUe=HVbmaQjRdDQ5TrRbU7YpA@mail.gmail.com>
Date:	Sun, 20 Jul 2014 12:07:34 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Jason Cooper <jason@...edaemon.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Commit d9e7972619334656 breaks KVM's virtio-rng-pci

On Sun, Jul 20, 2014 at 11:32 AM, Marcel Holtmann <marcel@...tmann.org> wrote:
> Hi Kees,
>
>>> the commit d9e7972619334656 ends up being responsible that using "-device virtio-rng-pci" in KVM no longer works.
>>>
>>>        From: Kees Cook <keescook@...omium.org>
>>>        Date: Mon, 3 Mar 2014 15:51:48 -0800
>>>        Subject: [PATCH] hwrng: add randomness to system from rng sources
>>>
>>>        When bringing a new RNG source online, it seems like it would make sense
>>>        to use some of its bytes to make the system entropy pool more random,
>>>        as done with all sorts of other devices that contain per-device or
>>>        per-boot differences.
>>>
>>> When providing "-device virtio-rng-pci" to a kernel with the above commit, the kernel never finishes booting. It just stops. My guess it is waiting for some magic entropy to appear.
>>>
>>> Maybe this is something that should be fixed in virtio-rng driver instead of reverting this patch, but I leave this to the experts in this area.
>>
>> Yup, this has already been handled. See various threads around:
>> https://lkml.org/lkml/2014/7/5/14
>
> I bisected 3.16-rc5 and it was not yet fixed there. It seems the fixes got merged less than 48 hours ago. Which means I just missed them. Tried with HEAD now and all looks good.

Great! Thanks for testing.

-Kees

-- 
Kees Cook
Chrome OS Security
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