File 0010-acpi-Don-t-register-the-acpi-command-when-locked-dow.patch of Package grub2.19065
From 53143c1ad9b5759774e2f5a1481a95c2888bfd18 Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm@redhat.com>
Date: Mon, 28 Sep 2020 20:08:41 +0200
Subject: [PATCH 10/41] acpi: Don't register the acpi command when locked down
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The command is not allowed when lockdown is enforced. Otherwise an
attacker can instruct the GRUB to load an SSDT table to overwrite
the kernel lockdown configuration and later load and execute
unsigned code.
Fixes: CVE-2020-14372
Reported-by: Máté Kukri <km@mkukri.xyz>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
docs/grub.texi | 5 +++++
grub-core/commands/acpi.c | 15 ++++++++-------
2 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/docs/grub.texi b/docs/grub.texi
index 951021867..6c67d55de 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -3907,6 +3907,11 @@ Normally, this command will replace the Root System Description Pointer
(RSDP) in the Extended BIOS Data Area to point to the new tables. If the
@option{--no-ebda} option is used, the new tables will be known only to
GRUB, but may be used by GRUB's EFI emulation.
+
+Note: The command is not allowed when lockdown is enforced (@pxref{Lockdown}).
+ Otherwise an attacker can instruct the GRUB to load an SSDT table to
+ overwrite the kernel lockdown configuration and later load and execute
+ unsigned code.
@end deffn
diff --git a/grub-core/commands/acpi.c b/grub-core/commands/acpi.c
index 9f02f2201..a2912989b 100644
--- a/grub-core/commands/acpi.c
+++ b/grub-core/commands/acpi.c
@@ -27,6 +27,7 @@
#include <grub/mm.h>
#include <grub/memory.h>
#include <grub/i18n.h>
+#include <grub/lockdown.h>
#ifdef GRUB_MACHINE_EFI
#include <grub/efi/efi.h>
@@ -775,13 +776,13 @@ static grub_extcmd_t cmd;
GRUB_MOD_INIT(acpi)
{
- cmd = grub_register_extcmd ("acpi", grub_cmd_acpi, 0,
- N_("[-1|-2] [--exclude=TABLE1,TABLE2|"
- "--load-only=TABLE1,TABLE2] FILE1"
- " [FILE2] [...]"),
- N_("Load host ACPI tables and tables "
- "specified by arguments."),
- options);
+ cmd = grub_register_extcmd_lockdown ("acpi", grub_cmd_acpi, 0,
+ N_("[-1|-2] [--exclude=TABLE1,TABLE2|"
+ "--load-only=TABLE1,TABLE2] FILE1"
+ " [FILE2] [...]"),
+ N_("Load host ACPI tables and tables "
+ "specified by arguments."),
+ options);
}
GRUB_MOD_FINI(acpi)
--
2.26.2
