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From 431a111c60095fc973d83fe9209f26f29ce78784 Mon Sep 17 00:00:00 2001
From: Hitendra Prajapati <hprajapati@mvista.com>
Date: Mon, 1 Aug 2022 11:17:17 +0530
Subject: [PATCH] CVE-2022-28736
Upstream-Status: Backport [https://git.savannah.gnu.org/gitweb/?p=grub.git;a=commit;h=04c86e0bb7b58fc2f913f798cdb18934933e532d]
CVE: CVE-2022-28736
Signed-off-by: Hitendra Prajapati <hprajapati@mvista.com>
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/commands/boot.c | 66 ++++++++++++++++++++++++++----
grub-core/loader/efi/chainloader.c | 46 +++++++++++----------
include/grub/loader.h | 5 +++
3 files changed, 87 insertions(+), 30 deletions(-)
diff --git a/grub-core/commands/boot.c b/grub-core/commands/boot.c
index bbca81e..6151478 100644
--- a/grub-core/commands/boot.c
+++ b/grub-core/commands/boot.c
@@ -27,10 +27,20 @@
GRUB_MOD_LICENSE ("GPLv3+");
-static grub_err_t (*grub_loader_boot_func) (void);
-static grub_err_t (*grub_loader_unload_func) (void);
+static grub_err_t (*grub_loader_boot_func) (void *context);
+static grub_err_t (*grub_loader_unload_func) (void *context);
+static void *grub_loader_context;
static int grub_loader_flags;
+struct grub_simple_loader_hooks
+{
+ grub_err_t (*boot) (void);
+ grub_err_t (*unload) (void);
+};
+
+/* Don't heap allocate this to avoid making grub_loader_set() fallible. */
+static struct grub_simple_loader_hooks simple_loader_hooks;
+
struct grub_preboot
{
grub_err_t (*preboot_func) (int);
@@ -44,6 +54,29 @@ static int grub_loader_loaded;
static struct grub_preboot *preboots_head = 0,
*preboots_tail = 0;
+static grub_err_t
+grub_simple_boot_hook (void *context)
+{
+ struct grub_simple_loader_hooks *hooks;
+
+ hooks = (struct grub_simple_loader_hooks *) context;
+ return hooks->boot ();
+}
+
+static grub_err_t
+grub_simple_unload_hook (void *context)
+{
+ struct grub_simple_loader_hooks *hooks;
+ grub_err_t ret;
+
+ hooks = (struct grub_simple_loader_hooks *) context;
+
+ ret = hooks->unload ();
+ grub_memset (hooks, 0, sizeof (*hooks));
+
+ return ret;
+}
+
int
grub_loader_is_loaded (void)
{
@@ -110,28 +143,45 @@ grub_loader_unregister_preboot_hook (struct grub_preboot *hnd)
}
void
-grub_loader_set (grub_err_t (*boot) (void),
- grub_err_t (*unload) (void),
- int flags)
+grub_loader_set_ex (grub_err_t (*boot) (void *context),
+ grub_err_t (*unload) (void *context),
+ void *context,
+ int flags)
{
if (grub_loader_loaded && grub_loader_unload_func)
- grub_loader_unload_func ();
+ grub_loader_unload_func (grub_loader_context);
grub_loader_boot_func = boot;
grub_loader_unload_func = unload;
+ grub_loader_context = context;
grub_loader_flags = flags;
grub_loader_loaded = 1;
}
+void
+grub_loader_set (grub_err_t (*boot) (void),
+ grub_err_t (*unload) (void),
+ int flags)
+{
+ grub_loader_set_ex (grub_simple_boot_hook,
+ grub_simple_unload_hook,
+ &simple_loader_hooks,
+ flags);
+
+ simple_loader_hooks.boot = boot;
+ simple_loader_hooks.unload = unload;
+}
+
void
grub_loader_unset(void)
{
if (grub_loader_loaded && grub_loader_unload_func)
- grub_loader_unload_func ();
+ grub_loader_unload_func (grub_loader_context);
grub_loader_boot_func = 0;
grub_loader_unload_func = 0;
+ grub_loader_context = 0;
grub_loader_loaded = 0;
}
@@ -158,7 +208,7 @@ grub_loader_boot (void)
return err;
}
}
- err = (grub_loader_boot_func) ();
+ err = (grub_loader_boot_func) (grub_loader_context);
for (cur = preboots_tail; cur; cur = cur->prev)
if (! err)
diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c
index a8d7b91..93a028a 100644
--- a/grub-core/loader/efi/chainloader.c
+++ b/grub-core/loader/efi/chainloader.c
@@ -44,33 +44,28 @@ GRUB_MOD_LICENSE ("GPLv3+");
static grub_dl_t my_mod;
-static grub_efi_physical_address_t address;
-static grub_efi_uintn_t pages;
-static grub_efi_device_path_t *file_path;
-static grub_efi_handle_t image_handle;
-static grub_efi_char16_t *cmdline;
-
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;
+ loaded_image = grub_efi_get_loaded_image (image_handle);
+ if (loaded_image != NULL)
+ grub_free (loaded_image->load_options);
+
b = grub_efi_system_table->boot_services;
efi_call_1 (b->unload_image, image_handle);
- efi_call_2 (b->free_pages, address, pages);
-
- grub_free (file_path);
- grub_free (cmdline);
- cmdline = 0;
- file_path = 0;
grub_dl_unref (my_mod);
return GRUB_ERR_NONE;
}
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;
@@ -139,7 +134,7 @@ make_file_path (grub_efi_device_path_t *dp, const char *filename)
char *dir_start;
char *dir_end;
grub_size_t size;
- grub_efi_device_path_t *d;
+ grub_efi_device_path_t *d, *file_path;
dir_start = grub_strchr (filename, ')');
if (! dir_start)
@@ -215,11 +210,15 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
grub_efi_status_t status;
grub_efi_boot_services_t *b;
grub_device_t dev = 0;
- grub_efi_device_path_t *dp = 0;
+ grub_efi_device_path_t *dp = NULL, *file_path = NULL;
grub_efi_loaded_image_t *loaded_image;
char *filename;
void *boot_image = 0;
grub_efi_handle_t dev_handle = 0;
+ 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"));
@@ -227,11 +226,6 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
grub_dl_ref (my_mod);
- /* Initialize some global variables. */
- address = 0;
- image_handle = 0;
- file_path = 0;
-
b = grub_efi_system_table->boot_services;
file = grub_file_open (filename, GRUB_FILE_TYPE_EFI_CHAINLOADED_IMAGE);
@@ -401,7 +395,11 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
grub_file_close (file);
grub_device_close (dev);
- grub_loader_set (grub_chainloader_boot, grub_chainloader_unload, 0);
+ /* We're finished with the source image buffer and file path now. */
+ efi_call_2 (b->free_pages, address, pages);
+ grub_free (file_path);
+
+ grub_loader_set_ex (grub_chainloader_boot, grub_chainloader_unload, image_handle, 0);
return 0;
fail:
@@ -412,11 +410,15 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
if (file)
grub_file_close (file);
+ grub_free (cmdline);
grub_free (file_path);
if (address)
efi_call_2 (b->free_pages, address, pages);
+ if (image_handle != NULL)
+ efi_call_1 (b->unload_image, image_handle);
+
grub_dl_unref (my_mod);
return grub_errno;
diff --git a/include/grub/loader.h b/include/grub/loader.h
index 7f82a49..3071a50 100644
--- a/include/grub/loader.h
+++ b/include/grub/loader.h
@@ -39,6 +39,11 @@ void EXPORT_FUNC (grub_loader_set) (grub_err_t (*boot) (void),
grub_err_t (*unload) (void),
int flags);
+void EXPORT_FUNC (grub_loader_set_ex) (grub_err_t (*boot) (void *context),
+ grub_err_t (*unload) (void *context),
+ void *context,
+ int flags);
+
/* Unset current loader, if any. */
void EXPORT_FUNC (grub_loader_unset) (void);
--
2.25.1
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