linux-kernel - Re: [PATCH V38 15/29] acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down

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Date:   Wed, 14 Aug 2019 19:47:32 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Matthew Garrett <mjg59@...gle.com>
Cc:     James Morris <jmorris@...ei.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Josh Boyer <jwboyer@...hat.com>,
        David Howells <dhowells@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Dave Young <dyoung@...hat.com>, linux-acpi@...r.kernel.org
Subject: Re: [PATCH V38 15/29] acpi: Ignore acpi_rsdp kernel param when the
 kernel has been locked down

On Wed, Aug 14, 2019 at 10:14:54AM -0700, Matthew Garrett wrote:
> We explicitly don't want to pay attention to the acpi_rsdp kernel
> parameter in early boot except for the case of finding the SRAT table,
> and we only need that if CONFIG_RANDOMIZE_BASE and
> CONFIG_MEMORY_HOTREMOVE are set. However, we *do* want to tell the
> actual kernel where the RSDP is if we found it via some other means,
> so we can't just clear the boot parameters value.

Ok.

> The kernel proper will parse the command line again and will then (if
> lockdown isn't enabled) override the actual value we passed up in boot
> params.

Yeah, ok, I see what you're doing there. AFAICT, you do that in

setup_arch->acpi_boot_table_init-> ... -> acpi_os_get_root_pointer()

I hope nothing needs it earlier because then we'll have to restructure
again...

Thx.

-- 
Regards/Gruss,
    Boris.

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