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From 19b4f19cfea30655032c978e228d78e056f55f1a Mon Sep 17 00:00:00 2001
From: Chris Coulson <chris.coulson@canonical.com>
Date: Tue, 5 Apr 2022 11:48:58 +0100
Subject: loader/efi/chainloader: Use grub_loader_set_ex()
This ports the EFI chainloader to use grub_loader_set_ex() in order to fix
a use-after-free bug that occurs when grub_cmd_chainloader() is executed
more than once before a boot attempt is performed.
Fixes: CVE-2022-28736
Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
grub-core/loader/efi/chainloader.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c
index d1602c89b..7557eb269 100644
--- a/grub-core/loader/efi/chainloader.c
+++ b/grub-core/loader/efi/chainloader.c
@@ -44,11 +44,10 @@ GRUB_MOD_LICENSE ("GPLv3+");
static grub_dl_t my_mod;
-static grub_efi_handle_t image_handle;
-
static grub_err_t
-grub_chainloader_unload (void)
+grub_chainloader_unload (void *context)
{
+ grub_efi_handle_t image_handle = (grub_efi_handle_t) context;
grub_efi_loaded_image_t *loaded_image;
grub_efi_boot_services_t *b;
@@ -64,8 +63,9 @@ grub_chainloader_unload (void)
}
static grub_err_t
-grub_chainloader_boot (void)
+grub_chainloader_boot (void *context)
{
+ grub_efi_handle_t image_handle = (grub_efi_handle_t) context;
grub_efi_boot_services_t *b;
grub_efi_status_t status;
grub_efi_uintn_t exit_data_size;
@@ -225,6 +225,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
grub_efi_physical_address_t address = 0;
grub_efi_uintn_t pages = 0;
grub_efi_char16_t *cmdline = NULL;
+ grub_efi_handle_t image_handle = NULL;
if (argc == 0)
return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
@@ -405,7 +406,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
efi_call_2 (b->free_pages, address, pages);
grub_free (file_path);
- grub_loader_set (grub_chainloader_boot, grub_chainloader_unload, 0);
+ grub_loader_set_ex (grub_chainloader_boot, grub_chainloader_unload, image_handle, 0);
return 0;
fail:
@@ -423,10 +424,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
efi_call_2 (b->free_pages, address, pages);
if (image_handle != NULL)
- {
- efi_call_1 (b->unload_image, image_handle);
- image_handle = NULL;
- }
+ efi_call_1 (b->unload_image, image_handle);
grub_dl_unref (my_mod);
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