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

From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Aditya Garg <gargaditya08@live.com>
Cc: Ard Biesheuvel <ardb@kernel.org>, Jeremy Kerr <jk@ozlabs.org>,
	"joeyli.kernel@gmail.com" <joeyli.kernel@gmail.com>,
	"zohar@linux.ibm.com" <zohar@linux.ibm.com>,
	"jmorris@namei.org" <jmorris@namei.org>,
	"eric.snowberg@oracle.com" <eric.snowberg@oracle.com>,
	"dhowells@redhat.com" <dhowells@redhat.com>,
	"jlee@suse.com" <jlee@suse.com>,
	"James.Bottomley@hansenpartnership.com" 
	<James.Bottomley@HansenPartnership.com>,
	"jarkko@kernel.org" <jarkko@kernel.org>,
	"mic@digikod.net" <mic@digikod.net>,
	"dmitry.kasatkin@gmail.com" <dmitry.kasatkin@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"linux-efi@vger.kernel.org" <linux-efi@vger.kernel.org>,
	"linux-security-module@vger.kernel.org" 
	<linux-security-module@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"keyrings@vger.kernel.org" <keyrings@vger.kernel.org>,
	"linux-integrity@vger.kernel.org"
	<linux-integrity@vger.kernel.org>,
	Orlando Chamberlain <redecorating@protonmail.com>,
	Aun-Ali Zaidi <admin@kodeit.net>
Subject: Re: [PATCH] efi: Do not import certificates from UEFI Secure Boot for T2 Macs
Date: Fri, 11 Feb 2022 16:28:57 +0000	[thread overview]
Message-ID: <20220211162857.GB10606@srcf.ucam.org> (raw)
In-Reply-To: <99BB011C-71DE-49FA-81CB-BE2AC9613030@live.com>

On Fri, Feb 11, 2022 at 04:51:22AM +0000, Aditya Garg wrote:

> With this patch, I built 2 kernels, one with CONFIG_LOAD_UEFI_KEYS=y and other with CONFIG_LOAD_UEFI_KEYS=n. I have got different variables causing panics in both cases. The logs couldn't get saved in journalctl so, I clicked a picture of the same. The kernel anyways was refusing to boot after these logs.

Oh gosh I'm an idiot. Please try this one instead.

diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
index f3e54f6616f0..79a003c2f7b6 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -32,6 +32,8 @@
 #include <linux/stringify.h>
 #include <linux/workqueue.h>
 #include <linux/completion.h>
+#include <linux/ucs2_string.h>
+#include <linux/slab.h>
 
 #include <asm/efi.h>
 
@@ -179,6 +181,9 @@ static void efi_call_rts(struct work_struct *work)
 {
 	void *arg1, *arg2, *arg3, *arg4, *arg5;
 	efi_status_t status = EFI_NOT_FOUND;
+	unsigned long utf8_name_size;
+	char *utf8_name;
+	char guid_str[UUID_STRING_LEN + 1];
 
 	arg1 = efi_rts_work.arg1;
 	arg2 = efi_rts_work.arg2;
@@ -203,6 +208,17 @@ static void efi_call_rts(struct work_struct *work)
 				       (efi_time_t *)arg2);
 		break;
 	case EFI_GET_VARIABLE:
+		utf8_name_size = ucs2_utf8size((efi_char16_t *)arg1);
+		utf8_name = kmalloc(utf8_name_size+1, GFP_KERNEL);
+		if (!utf8_name) {
+			printk(KERN_INFO "failed to allocate UTF8 buffer\n");
+			break;
+		}
+
+		ucs2_as_utf8(utf8_name, (efi_char16_t *)arg1, utf8_name_size + 1);
+		efi_guid_to_str((efi_guid_t *)arg2, guid_str);
+
+		printk(KERN_INFO "Reading EFI variable %s-%s\n", utf8_name, guid_str);
 		status = efi_call_virt(get_variable, (efi_char16_t *)arg1,
 				       (efi_guid_t *)arg2, (u32 *)arg3,
 				       (unsigned long *)arg4, (void *)arg5);

