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

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Message-ID: <CAGXu5jJbrEryxx7e48Mc0Pi18vEBfHWN-pOxrvDnC24Lr21ghQ@mail.gmail.com>
Date:	Sun, 20 Jul 2014 10:39:51 -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 9:18 AM, Marcel Holtmann <marcel@...tmann.org> wrote:
> Hello,
>
> 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

-Kees

-- 
Kees Cook
Chrome OS Security
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