From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Chris Coulson <chris.coulson@canonical.com>

Date: Fri, 29 Apr 2022 21:30:56 +0100

Subject: [PATCH] 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.

Signed-off-by: Chris Coulson <chris.coulson@canonical.com>

(cherry picked from commit 4b7f0402b7cb0f67a93be736f2b75b818d7f44c9)

[rharwood: context sludge from other change]

Signed-off-by: Robbie Harwood <rharwood@redhat.com>

---

 grub-core/loader/efi/chainloader.c | 38 ++++++++++++++++++++++----------------

 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c

index 3342492ff1..fb874f1855 100644

--- a/grub-core/loader/efi/chainloader.c

+++ b/grub-core/loader/efi/chainloader.c

@@ -48,8 +48,6 @@ GRUB_MOD_LICENSE ("GPLv3+");

 static grub_dl_t my_mod;

-static grub_efi_handle_t image_handle;

-

 struct grub_secureboot_chainloader_context {

   grub_efi_physical_address_t address;

   grub_efi_uintn_t pages;

@@ -59,7 +57,6 @@ struct grub_secureboot_chainloader_context {

   grub_ssize_t cmdline_len;

   grub_efi_handle_t dev_handle;

 };

-static struct grub_secureboot_chainloader_context *sb_context;

 static grub_err_t

 grub_start_image (grub_efi_handle_t handle)

@@ -98,11 +95,14 @@ grub_start_image (grub_efi_handle_t handle)

 }

 static grub_err_t

-grub_chainloader_unload (void)

+grub_chainloader_unload (void *context)

 {

+  grub_efi_handle_t image_handle;

   grub_efi_loaded_image_t *loaded_image;

   grub_efi_boot_services_t *b;

+  image_handle = (grub_efi_handle_t) context;

+

   loaded_image = grub_efi_get_loaded_image (image_handle);

   if (loaded_image != NULL)

     grub_free (loaded_image->load_options);

@@ -115,10 +115,12 @@ grub_chainloader_unload (void)

 }

 static grub_err_t

-grub_chainloader_boot (void)

+grub_chainloader_boot (void *context)

 {

+  grub_efi_handle_t image_handle;

   grub_err_t err;

+  image_handle = (grub_efi_handle_t) context;

   err = grub_start_image (image_handle);

   grub_loader_unset ();

@@ -839,15 +841,17 @@ error_exit:

 }

 static grub_err_t

-grub_secureboot_chainloader_unload (void)

+grub_secureboot_chainloader_unload (void *context)

 {

+  struct grub_secureboot_chainloader_context *sb_context;

+

+  sb_context = (struct grub_secureboot_chainloader_context *) context;

+

   grub_efi_free_pages (sb_context->address, sb_context->pages);

   grub_free (sb_context->file_path);

   grub_free (sb_context->cmdline);

   grub_free (sb_context);

-  sb_context = 0;

-

   grub_dl_unref (my_mod);

   return GRUB_ERR_NONE;

 }

@@ -896,12 +900,15 @@ grub_load_image(grub_efi_device_path_t *file_path, void *boot_image,

 }

 static grub_err_t

-grub_secureboot_chainloader_boot (void)

+grub_secureboot_chainloader_boot (void *context)

 {

+  struct grub_secureboot_chainloader_context *sb_context;

   grub_efi_boot_services_t *b;

   int rc;

   grub_efi_handle_t handle = 0;

+  sb_context = (struct grub_secureboot_chainloader_context *) context;

+

   rc = handle_image (sb_context);

   if (rc == 0)

     {

@@ -942,6 +949,8 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),

   grub_efi_char16_t *cmdline = 0;

   grub_ssize_t cmdline_len = 0;

   grub_efi_handle_t dev_handle = 0;

+  grub_efi_handle_t image_handle = 0;

+  struct grub_secureboot_chainloader_context *sb_context = 0;

   if (argc == 0)

     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));

@@ -1127,8 +1136,8 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),

       grub_file_close (file);

       grub_device_close (dev);

-      grub_loader_set (grub_secureboot_chainloader_boot,

-		       grub_secureboot_chainloader_unload, 0);

+      grub_loader_set_ex (grub_secureboot_chainloader_boot,

+			  grub_secureboot_chainloader_unload, sb_context, 0);

       return 0;

     }

   else

@@ -1142,7 +1151,7 @@ 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;

     }

@@ -1169,10 +1178,7 @@ fail:

     grub_free (cmdline);

   if (image_handle != 0)

-    {

-      efi_call_1 (b->unload_image, image_handle);

-      image_handle = 0;

-    }

+    efi_call_1 (b->unload_image, image_handle);

   grub_dl_unref (my_mod);