linux-kernel - Re: [PATCH 0/3] Allow access to confidential computing secret area in SEV guests

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Date:   Thu, 02 Sep 2021 07:35:10 -0700
From:   James Bottomley <jejb@...ux.ibm.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Dov Murik <dovmurik@...ux.ibm.com>
Cc:     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>,
        Ard Biesheuvel <ardb@...nel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Tobin Feldman-Fitzthum <tobin@...ux.ibm.com>,
        Jim Cadden <jcadden@....com>, linux-coco@...ts.linux.dev,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Allow access to confidential computing secret area
 in SEV guests

On Thu, 2021-09-02 at 14:57 +0200, Greg KH wrote:
[...]
> Wait, why are you using securityfs for this?
> 
> securityfs is for LSMs to use. 

No it isn't ... at least not exclusively; we use it for non LSM
security purposes as well, like for the TPM BIOS log and for IMA.  What
makes you think we should start restricting securityfs to LSMs only? 
That's not been the policy up to now.
 
>  If you want your own filesystem to play around with stuff like this,
> great, write your own, it's only 200 lines or less these days.  We
> used to do it all the time until people realized they should just use
> sysfs for driver stuff.

This is a security purpose (injected key retrieval), so securityfs
seems to be the best choice.  It's certainly possible to create a new
filesystem, but I really think things with a security purpose should
use securityfs so people know where to look for them.

James


> But this isn't a driver, so sure, add your own virtual filesystem,
> mount it somewhere and away you go, no messing around with
> securityfs, right?
> 
> thanks,
> 
> greg k-h