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

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Message-ID: <CAMj1kXE6aObn7hGneGMMiJ-ss7YaiYDFL+HqktYt2WMUpZnFjQ@mail.gmail.com>
Date:   Fri, 7 Oct 2022 17:06:44 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc:     Kees Cook <keescook@...omium.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, 7 Oct 2022 at 15:46, Guilherme G. Piccoli <gpiccoli@...lia.com> 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?

Well, I did spot this oddity

        efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
        if (!efi_pstore_info.buf)
                return -ENOMEM;

       efi_pstore_info.bufsize = 1024;

So that hardcoded 4096 looks odd, but at least it is larger than the
default 1024. So what happens if you increase the record size to >
4096?