1From 04c86e0bb7b58fc2f913f798cdb18934933e532d Mon Sep 17 00:00:00 2001
2From: Chris Coulson <chris.coulson@canonical.com>
3Date: Tue, 5 Apr 2022 11:48:58 +0100
4Subject: [PATCH] loader/efi/chainloader: Use grub_loader_set_ex()
5
6This ports the EFI chainloader to use grub_loader_set_ex() in order to fix
7a use-after-free bug that occurs when grub_cmd_chainloader() is executed
8more than once before a boot attempt is performed.
9
10Fixes: CVE-2022-28736
11
12Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
13Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
14
15Upstream-Status: Backport
16CVE: CVE-2022-28736
17
18Reference to upstream patch:
19https://git.savannah.gnu.org/cgit/grub.git/commit/?id=04c86e0bb7b58fc2f913f798cdb18934933e532d
20
21Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com>
22---
23 grub-core/loader/efi/chainloader.c | 16 +++++++---------
24 1 file changed, 7 insertions(+), 9 deletions(-)
25
26diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c
27index d1602c89b..7557eb269 100644
28--- a/grub-core/loader/efi/chainloader.c
29+++ b/grub-core/loader/efi/chainloader.c
30@@ -44,11 +44,10 @@ GRUB_MOD_LICENSE ("GPLv3+");
31
32 static grub_dl_t my_mod;
33
34-static grub_efi_handle_t image_handle;
35-
36 static grub_err_t
37-grub_chainloader_unload (void)
38+grub_chainloader_unload (void *context)
39 {
40+  grub_efi_handle_t image_handle = (grub_efi_handle_t) context;
41   grub_efi_loaded_image_t *loaded_image;
42   grub_efi_boot_services_t *b;
43
44@@ -64,8 +63,9 @@ grub_chainloader_unload (void)
45 }
46
47 static grub_err_t
48-grub_chainloader_boot (void)
49+grub_chainloader_boot (void *context)
50 {
51+  grub_efi_handle_t image_handle = (grub_efi_handle_t) context;
52   grub_efi_boot_services_t *b;
53   grub_efi_status_t status;
54   grub_efi_uintn_t exit_data_size;
55@@ -225,6 +225,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
56   grub_efi_physical_address_t address = 0;
57   grub_efi_uintn_t pages = 0;
58   grub_efi_char16_t *cmdline = NULL;
59+  grub_efi_handle_t image_handle = NULL;
60
61   if (argc == 0)
62     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
63@@ -405,7 +406,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
64   efi_call_2 (b->free_pages, address, pages);
65   grub_free (file_path);
66
67-  grub_loader_set (grub_chainloader_boot, grub_chainloader_unload, 0);
68+  grub_loader_set_ex (grub_chainloader_boot, grub_chainloader_unload, image_handle, 0);
69   return 0;
70
71  fail:
72@@ -423,10 +424,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
73     efi_call_2 (b->free_pages, address, pages);
74
75   if (image_handle != NULL)
76-    {
77-      efi_call_1 (b->unload_image, image_handle);
78-      image_handle = NULL;
79-    }
80+    efi_call_1 (b->unload_image, image_handle);
81
82   grub_dl_unref (my_mod);
83
84--
852.34.1
86
87