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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Chris Coulson <chris.coulson@canonical.com>
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Date: Fri, 29 Apr 2022 21:30:56 +0100
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Subject: [PATCH] loader/efi/chainloader: Use grub_loader_set_ex
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This ports the EFI chainloader to use grub_loader_set_ex in order to fix
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a use-after-free bug that occurs when grub_cmd_chainloader is executed
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more than once before a boot attempt is performed.
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Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
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(cherry picked from commit 4b7f0402b7cb0f67a93be736f2b75b818d7f44c9)
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[rharwood: context sludge from other change]
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Signed-off-by: Robbie Harwood <rharwood@redhat.com>
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---
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 grub-core/loader/efi/chainloader.c | 38 ++++++++++++++++++++++----------------
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 1 file changed, 22 insertions(+), 16 deletions(-)
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diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c
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index 3342492ff1..fb874f1855 100644
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--- a/grub-core/loader/efi/chainloader.c
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+++ b/grub-core/loader/efi/chainloader.c
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@@ -48,8 +48,6 @@ GRUB_MOD_LICENSE ("GPLv3+");
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 static grub_dl_t my_mod;
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-static grub_efi_handle_t image_handle;
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-
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 struct grub_secureboot_chainloader_context {
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   grub_efi_physical_address_t address;
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   grub_efi_uintn_t pages;
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@@ -59,7 +57,6 @@ struct grub_secureboot_chainloader_context {
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   grub_ssize_t cmdline_len;
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   grub_efi_handle_t dev_handle;
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 };
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-static struct grub_secureboot_chainloader_context *sb_context;
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 static grub_err_t
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 grub_start_image (grub_efi_handle_t handle)
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@@ -98,11 +95,14 @@ grub_start_image (grub_efi_handle_t handle)
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 }
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 static grub_err_t
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-grub_chainloader_unload (void)
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+grub_chainloader_unload (void *context)
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 {
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+  grub_efi_handle_t image_handle;
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   grub_efi_loaded_image_t *loaded_image;
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   grub_efi_boot_services_t *b;
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+  image_handle = (grub_efi_handle_t) context;
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+
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   loaded_image = grub_efi_get_loaded_image (image_handle);
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   if (loaded_image != NULL)
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     grub_free (loaded_image->load_options);
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@@ -115,10 +115,12 @@ grub_chainloader_unload (void)
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 }
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 static grub_err_t
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-grub_chainloader_boot (void)
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+grub_chainloader_boot (void *context)
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 {
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+  grub_efi_handle_t image_handle;
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   grub_err_t err;
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+  image_handle = (grub_efi_handle_t) context;
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   err = grub_start_image (image_handle);
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   grub_loader_unset ();
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@@ -839,15 +841,17 @@ error_exit:
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 }
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 static grub_err_t
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-grub_secureboot_chainloader_unload (void)
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+grub_secureboot_chainloader_unload (void *context)
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 {
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+  struct grub_secureboot_chainloader_context *sb_context;
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+
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+  sb_context = (struct grub_secureboot_chainloader_context *) context;
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+
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   grub_efi_free_pages (sb_context->address, sb_context->pages);
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   grub_free (sb_context->file_path);
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   grub_free (sb_context->cmdline);
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   grub_free (sb_context);
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-  sb_context = 0;
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-
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   grub_dl_unref (my_mod);
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   return GRUB_ERR_NONE;
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 }
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@@ -896,12 +900,15 @@ grub_load_image(grub_efi_device_path_t *file_path, void *boot_image,
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 }
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 static grub_err_t
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-grub_secureboot_chainloader_boot (void)
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+grub_secureboot_chainloader_boot (void *context)
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 {
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+  struct grub_secureboot_chainloader_context *sb_context;
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   grub_efi_boot_services_t *b;
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   int rc;
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   grub_efi_handle_t handle = 0;
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+  sb_context = (struct grub_secureboot_chainloader_context *) context;
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+
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   rc = handle_image (sb_context);
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   if (rc == 0)
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     {
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@@ -942,6 +949,8 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
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   grub_efi_char16_t *cmdline = 0;
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   grub_ssize_t cmdline_len = 0;
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   grub_efi_handle_t dev_handle = 0;
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+  grub_efi_handle_t image_handle = 0;
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+  struct grub_secureboot_chainloader_context *sb_context = 0;
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   if (argc == 0)
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     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
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@@ -1127,8 +1136,8 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
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       grub_file_close (file);
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       grub_device_close (dev);
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-      grub_loader_set (grub_secureboot_chainloader_boot,
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-		       grub_secureboot_chainloader_unload, 0);
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+      grub_loader_set_ex (grub_secureboot_chainloader_boot,
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+			  grub_secureboot_chainloader_unload, sb_context, 0);
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       return 0;
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     }
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   else
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@@ -1142,7 +1151,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),
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       efi_call_2 (b->free_pages, address, pages);
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       grub_free (file_path);
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-      grub_loader_set (grub_chainloader_boot, grub_chainloader_unload, 0);
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+      grub_loader_set_ex (grub_chainloader_boot, grub_chainloader_unload, image_handle, 0);
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       return 0;
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     }
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@@ -1169,10 +1178,7 @@ fail:
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     grub_free (cmdline);
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   if (image_handle != 0)
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-    {
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-      efi_call_1 (b->unload_image, image_handle);
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-      image_handle = 0;
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-    }
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+    efi_call_1 (b->unload_image, image_handle);
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   grub_dl_unref (my_mod);
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