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From 584263eca1546e5cab69ba6fe7b4b07df2630a21 Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm@redhat.com>
Date: Wed, 14 Oct 2020 16:33:42 +0200
Subject: [PATCH] mmap: Don't register cutmem and badram commands when lockdown
is enforced
The cutmem and badram commands can be used to remove EFI memory regions
and potentially disable the UEFI Secure Boot. Prevent the commands to be
registered if the GRUB is locked down.
Fixes: CVE-2020-27779
Reported-by: Teddy Reed <teddy.reed@gmail.com>
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=d298b41f90cbf1f2e5a10e29daa1fc92ddee52c9]
CVE: CVE-2020-27779
Signed-off-by: Marta Rybczynska <marta.rybczynska@huawei.com>
---
docs/grub.texi | 4 ++++
grub-core/mmap/mmap.c | 13 +++++++------
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/docs/grub.texi b/docs/grub.texi
index 47ac7ff..a1aaee6 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -4051,6 +4051,10 @@ this page is to be filtered. This syntax makes it easy to represent patterns
that are often result of memory damage, due to physical distribution of memory
cells.
+Note: The command is not allowed when lockdown is enforced (@pxref{Lockdown}).
+ This prevents removing EFI memory regions to potentially subvert the
+ security mechanisms provided by the UEFI secure boot.
+
@node blocklist
@subsection blocklist
diff --git a/grub-core/mmap/mmap.c b/grub-core/mmap/mmap.c
index 57b4e9a..7ebf32e 100644
--- a/grub-core/mmap/mmap.c
+++ b/grub-core/mmap/mmap.c
@@ -20,6 +20,7 @@
#include <grub/memory.h>
#include <grub/machine/memory.h>
#include <grub/err.h>
+#include <grub/lockdown.h>
#include <grub/misc.h>
#include <grub/mm.h>
#include <grub/command.h>
@@ -534,12 +535,12 @@ static grub_command_t cmd, cmd_cut;
GRUB_MOD_INIT(mmap)
{
- cmd = grub_register_command ("badram", grub_cmd_badram,
- N_("ADDR1,MASK1[,ADDR2,MASK2[,...]]"),
- N_("Declare memory regions as faulty (badram)."));
- cmd_cut = grub_register_command ("cutmem", grub_cmd_cutmem,
- N_("FROM[K|M|G] TO[K|M|G]"),
- N_("Remove any memory regions in specified range."));
+ cmd = grub_register_command_lockdown ("badram", grub_cmd_badram,
+ N_("ADDR1,MASK1[,ADDR2,MASK2[,...]]"),
+ N_("Declare memory regions as faulty (badram)."));
+ cmd_cut = grub_register_command_lockdown ("cutmem", grub_cmd_cutmem,
+ N_("FROM[K|M|G] TO[K|M|G]"),
+ N_("Remove any memory regions in specified range."));
}
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