linux-kernel - Re: [PATCH 2/2] x86, microcode: Add option to allow downgrading of microcode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 25 Jan 2014 19:14:09 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 2/2] x86, microcode: Add option to allow downgrading of
 microcode

On Sat, Jan 25, 2014 at 02:35:58PM -0200, Henrique de Moraes Holschuh wrote:
> On Fri, 24 Jan 2014, Andi Kleen wrote:
> > For testing purposes it can be useful to downgrade microcode.
> > Normally the driver only allows upgrading.
> 
> The code is not prepared to work correctly when downgrading is allowed, in
> the presence of shadowed microcode.  When a firmware request results in more

As I wrote it's only for testing purposes when you know what you're doing
(typically with a special micro code file)

Your whole argument is irrelevant, as it only applies to normal users
who should never use this option.

> Also, since you're going to mess with this, why don't you implement the
> correct semanthics for microcode with the sign bit set?  Making it signed
> actually makes the current code behaviour worse.
> 
> Refer to: http://lkml.org/lkml/2011/3/21/522

I don't think it makes it worse. In fact I'm essentially implementing
Burt's request "for explicit user action" with the new override option.

Anyways I suppose your rant killed the patch anyways. Congratulations!

-Andi
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/