linux-kernel - Re: [PATCH 8/8] efi: pstore: Add module parameter for setting the record size

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Message-ID: <202210071230.63CF832@keescook>
Date:   Fri, 7 Oct 2022 12:32:34 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, kernel-dev@...lia.com,
        kernel@...ccoli.net, anton@...msg.org, ccross@...roid.com,
        tony.luck@...el.com, linux-efi@...r.kernel.org
Subject: Re: [PATCH 8/8] efi: pstore: Add module parameter for setting the
 record size

On Fri, Oct 07, 2022 at 10:45:33AM -0300, Guilherme G. Piccoli wrote:
> On 07/10/2022 10:19, Ard Biesheuvel wrote:
> > [...]
> > 
> > OVMF has
> > 
> > OvmfPkg/OvmfPkgX64.dsc:
> > gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x2000
> > OvmfPkg/OvmfPkgX64.dsc:
> > gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x8400
> > 
> > where the first one is without secure boot and the second with secure boot.
> > 
> > Interestingly, the default is
> > 
> > gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize|0x400
> > 
> > so this is probably where this 1k number comes from. So perhaps it is
> > better to leave it at 1k after all :-(
> > 
> 
> Oh darn...
> 
> So, let's stick with 1024 then? If so, no need for re-submitting right?

Given OVMF showing this as a max, it doesn't seem right to also make
this a minimum? Perhaps choose a different minimum to be enforced.

Also, can you update the commit log with Ard's archeology on
gEfiMdeModulePkgTokenSpaceGuid.PcdMaxVariableSize ?

-- 
Kees Cook