linux-kernel - Re: [PATCH v7 4/5] efi: Load efi_secret module if EFI secret area is populated

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Message-ID: <20220203121117.aedtaxspnm5mbqhj@sirius.home.kraxel.org>
Date:   Thu, 3 Feb 2022 13:11:17 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     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>,
        Greg KH <gregkh@...uxfoundation.org>,
        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>,
        James Bottomley <jejb@...ux.ibm.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@...r.kernel.org
Subject: Re: [PATCH v7 4/5] efi: Load efi_secret module if EFI secret area is
 populated

  Hi,

> >> If we keep only the 'efi.coco_secret != EFI_INVALID_TABLE_ADDR' check,
> >> we'll get errors from efi_secret for every VM launch that doesn't
> >> undergo LAUNCH_SECRET.  I don't think that's good.
> > 
> > Well, if that is a common case the module could either print nothing or
> > log KERN_INFO level instead of KERN_ERROR.
> 
> What if the user doesn't inject a secret and doesn't include the
> efi_secret module at all in the initrd?  request_module("efi_secret")
> will fail.
> 
> I can ignore the error code of request_module("efi_secret") but that
> feels bad.

Looking at the error code returned by request_module should help to
figure what happened (module load failed / no secret present / something
else).

But, yes, module load errors are harmless in case there is no secret
present in the first place.  Hmm, tricky.  I don't see a way to solve
that without duplicating the checks.

I withdraw my objections.

Reviewed-by: Gerd Hoffmann <kraxel@...hat.com>

take care,
  Gerd