linux-kernel - Re: [PATCH v3] efi: Do not import certificates from UEFI Secure Boot for T2 Macs

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Message-ID: <20220213073924.GA7648@wunner.de>
Date:   Sun, 13 Feb 2022 08:39:24 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Aditya Garg <gargaditya08@...e.com>
Cc:     David Laight <David.Laight@...LAB.COM>,
        Ard Biesheuvel <ardb@...nel.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Jeremy Kerr <jk@...abs.org>,
        "joeyli.kernel@...il.com" <joeyli.kernel@...il.com>,
        "zohar@...ux.ibm.com" <zohar@...ux.ibm.com>,
        "jmorris@...ei.org" <jmorris@...ei.org>,
        "eric.snowberg@...cle.com" <eric.snowberg@...cle.com>,
        "dhowells@...hat.com" <dhowells@...hat.com>,
        "jlee@...e.com" <jlee@...e.com>,
        "James.Bottomley@...senpartnership.com" 
        <James.Bottomley@...senPartnership.com>,
        "jarkko@...nel.org" <jarkko@...nel.org>,
        "mic@...ikod.net" <mic@...ikod.net>,
        "dmitry.kasatkin@...il.com" <dmitry.kasatkin@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        Orlando Chamberlain <redecorating@...tonmail.com>,
        Aun-Ali Zaidi <admin@...eit.net>
Subject: Re: [PATCH v3] efi: Do not import certificates from UEFI Secure Boot
 for T2 Macs

On Thu, Feb 10, 2022 at 10:47:25AM +0000, Aditya Garg wrote:
> +/* Apple Macs with T2 Security chip don't support these UEFI variables.
> + * The T2 chip manages the Secure Boot and does not allow Linux to boot
> + * if it is turned on. If turned off, an attempt to get certificates
> + * causes a crash, so we simply return 0 for them in each function.
> + */
> +
> +static const struct dmi_system_id uefi_skip_cert[] = {
> +
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,1") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,2") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,3") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro15,4") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,1") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,2") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,3") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookPro16,4") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,1") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir8,2") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacBookAir9,1") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacMini8,1") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "MacPro7,1") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,1") },
> +	{ UEFI_QUIRK_SKIP_CERT("Apple Inc.", "iMac20,2") },
> +	{ }
> +};

The T2 is represented by a PCI device with ID 106B:1802.  I think it
would be more elegant to sense presence of that device instead of
hardcoding a long dmi list, i.e.:

static bool apple_t2_present(void)
{
	struct pci_dev *pdev;

	if (!x86_apple_machine)
		return false;

	pdev = pci_get_device(PCI_VENDOR_ID_APPLE, 0x1802, NULL);
	if (pdev) {
		pci_put_dev(pdev);
		return true;
	}

	return false;
}