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

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



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