linux-kernel - Re: 4.14 "random: add a config option to trust the CPU's hwrng"

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Date:   Thu, 7 Feb 2019 12:28:09 +0100
From:   Greg KH <greg@...ah.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     "Rantala, Tommi T. (Nokia - FI/Espoo)" <tommi.t.rantala@...ia.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tytso@....edu" <tytso@....edu>
Subject: Re: 4.14 "random: add a config option to trust the CPU's hwrng"

On Wed, Feb 06, 2019 at 02:26:13PM -0500, Sasha Levin wrote:
> On Wed, Feb 06, 2019 at 11:44:36AM +0000, Rantala, Tommi T. (Nokia - FI/Espoo) wrote:
> > Hi stable maintainers,
> > 
> > Can you consider including these "random" patches in 4.14.y?
> > 
> > These are very useful in fixing esp. first-bootup delays of VMs due to
> > entropy starvation.
> > 
> > 
> > commit 39a8883a2b989d1d21bd8dd99f5557f0c5e89694
> > Author: Theodore Ts'o <tytso@....edu>
> > Date:   Tue Jul 17 18:24:27 2018 -0400
> > 
> >    random: add a config option to trust the CPU's hwrng
> > 
> > commit 9b25436662d5fb4c66eb527ead53cab15f596ee0
> > Author: Kees Cook <keescook@...omium.org>
> > Date:   Mon Aug 27 14:51:54 2018 -0700
> > 
> >    random: make CPU trust a boot parameter
> 
> This really looks like a new feature to me. The "old" behaviour of not
> trusting RDRAND-like randomness was by-design rather than an oversight.

I agree with Sasha, this looks like a new feature.  If you really want
this new functionality, just use 4.19 or newer, right?

thanks,

greg k-h