Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751791AbaGGGJx (ORCPT ); Mon, 7 Jul 2014 02:09:53 -0400 Received: from mail-ob0-f176.google.com ([209.85.214.176]:55048 "EHLO mail-ob0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198AbaGGGJu (ORCPT ); Mon, 7 Jul 2014 02:09:50 -0400 MIME-Version: 1.0 In-Reply-To: <20140707055049.GA27024@grmbl.mre> References: <20140707055049.GA27024@grmbl.mre> Date: Sun, 6 Jul 2014 23:09:49 -0700 X-Google-Sender-Auth: tUa7YvSVdQYIZjTji9mEbYGuVFU Message-ID: Subject: Re: [PATCH v2 2/2] virtio: rng: ensure reads happen after successful probe From: Kees Cook To: Amit Shah Cc: LKML , Virtualization List , Rusty Russell , Herbert Xu , Jason Cooper , "# 3.4.x" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 6, 2014 at 10:51 PM, Amit Shah wrote: > On (Sun) 06 Jul 2014 [21:38:36], Kees Cook wrote: >> On Fri, Jul 4, 2014 at 10:34 PM, Amit Shah wrote: >> > The hwrng core asks for random data in the hwrng_register() call itself >> > from commit d9e7972619. This doesn't play well with virtio -- the >> > DRIVER_OK bit is only set by virtio core on a successful probe, and >> > we're not yet out of our probe routine when this call is made. This >> > causes the host to not acknowledge any requests we put in the virtqueue, >> > and the insmod or kernel boot process just waits for data to arrive from >> > the host, which never happens. >> >> Doesn't this mean that virtio-rng won't ever contribute entropy to the system? > > The initial randomness? Yes. But it'll start contributing entropy as > soon as it's used as the current source. How does that happen? I don't see an init function defined for it? -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/