Re: [PATCH v7 0/5] Allow guest access to EFI confidential computing secret area

From: Dov Murik <dovmurik@linux.ibm.com>
To: Matthew Garrett <mjg59@srcf.ucam.org>, Gerd Hoffmann <kraxel@redhat.com>
Cc: Ard Biesheuvel <ardb@kernel.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	James Bottomley <jejb@linux.ibm.com>,
	linux-efi <linux-efi@vger.kernel.org>,
	Borislav Petkov <bp@suse.de>, Ashish Kalra <ashish.kalra@amd.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	James Morris <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	Andi Kleen <ak@linux.intel.com>, Andrew Scull <ascull@google.com>,
	Dave Hansen <dave.hansen@intel.com>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	Lenny Szubowicz <lszubowi@redhat.com>,
	Peter Gonda <pgonda@google.com>,
	Tobin Feldman-Fitzthum <tobin@linux.ibm.com>,
	Jim Cadden <jcadden@ibm.com>,
	Daniele Buono <dbuono@linux.vnet.ibm.com>,
	linux-coco@lists.linux.dev,
	linux-security-module@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Nayna Jain <nayna@linux.ibm.com>,
	dougmill@linux.vnet.ibm.com, gcwilson@linux.ibm.com,
	gjoyce@ibm.com,
	"open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)"
	<linuxppc-dev@lists.ozlabs.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Daniel Axtens <dja@axtens.net>,
	Dov Murik <dovmurik@linux.ibm.com>
Subject: Re: [PATCH v7 0/5] Allow guest access to EFI confidential computing secret area
Date: Mon, 7 Feb 2022 20:50:48 +0200	[thread overview]
Message-ID: <3387b2e7-0921-cd80-279b-24d13f706443@linux.ibm.com> (raw)
In-Reply-To: <20220202084534.GA10247@srcf.ucam.org>

On 02/02/2022 10:45, Matthew Garrett wrote:
> On Wed, Feb 02, 2022 at 09:36:53AM +0100, Gerd Hoffmann wrote:
> 
>> Having a "secrets/" directory looks good to me.  Then the individual
>> implementations can either add files to the directory, i.e. efi_secrets
>> would create "secrets/<guid>" files.  Or each implementation creates a
>> subdirectory with the secrets, i.e. "secrets/coco/" and
>> "secrets/coco/<guid>".
> 
> I prefer a subdirectory, on the basis that we could conceivably end up 
> with more than one implementation on a single device at some point, and 
> also because it makes it trivial for userland to determine what the 
> source is which may make a semantic difference under certain 
> circumstances.
>  

OK, sounds good.  In the next round of the series the module will create
the files in <securityfs>/secrets/coco/ .

>> Longer-term (i.e once we have more than one implementation) we probably
>> need a separate module which owns and manages the "secrets/" directory,
>> and possibly provides some common helper functions too.
> 
> Agree.

Yes; one candidate for such helper function is a filesystem that
implements the "wipe file content from memory on unlink".

-Dov