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From 0d237c0b90f0c6d4a3662c569b2371ae3ed69574 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] acpi: Don't register the acpi command when locked down
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
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>
Upstream-Status: Backport [https://git.savannah.gnu.org/cgit/grub.git/commit/?id=3e8e4c0549240fa209acffceb473e1e509b50c95]
CVE: CVE-2020-14372
Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.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 0786427..47ac7ff 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -3986,6 +3986,11 @@ 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 5a1499a..1215f2a 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)
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