From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Dimitri John Ledkov <xnox@ubuntu.com>

Date: Fri, 11 Jun 2021 13:51:20 +0200

Subject: [PATCH] Allow chainloading EFI apps from loop mounts.

---

 grub-core/disk/loopback.c          |  9 +--------

 grub-core/loader/efi/chainloader.c | 23 +++++++++++++++++++++++

 include/grub/loopback.h            | 30 ++++++++++++++++++++++++++++++

 3 files changed, 54 insertions(+), 8 deletions(-)

 create mode 100644 include/grub/loopback.h

diff --git a/grub-core/disk/loopback.c b/grub-core/disk/loopback.c

index 41bebd14fe3..99f47924ec2 100644

--- a/grub-core/disk/loopback.c

+++ b/grub-core/disk/loopback.c

@@ -21,20 +21,13 @@

 #include <grub/misc.h>

 #include <grub/file.h>

 #include <grub/disk.h>

+#include <grub/loopback.h>

 #include <grub/mm.h>

 #include <grub/extcmd.h>

 #include <grub/i18n.h>

 GRUB_MOD_LICENSE ("GPLv3+");

-struct grub_loopback

-{

-  char *devname;

-  grub_file_t file;

-  struct grub_loopback *next;

-  unsigned long id;

-};

-

 static struct grub_loopback *loopback_list;

 static unsigned long last_id = 0;

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

index d41e8ea14a8..3af6b122926 100644

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

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

@@ -24,6 +24,7 @@

 #include <grub/err.h>

 #include <grub/device.h>

 #include <grub/disk.h>

+#include <grub/loopback.h>

 #include <grub/misc.h>

 #include <grub/charset.h>

 #include <grub/mm.h>

@@ -901,6 +902,7 @@ 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_device_t orig_dev = 0;

   grub_efi_device_path_t *dp = 0;

   char *filename;

   void *boot_image = 0;

@@ -958,6 +960,15 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),

   if (! dev)

     goto fail;

+  /* if device is loopback, use underlying dev */

+  if (dev->disk->dev->id == GRUB_DISK_DEVICE_LOOPBACK_ID)

+    {

+      struct grub_loopback *d;

+      orig_dev = dev;

+      d = dev->disk->data;

+      dev = d->file->device;

+    }

+

   if (dev->disk)

     dev_handle = grub_efidisk_get_device_handle (dev->disk);

   else if (dev->net && dev->net->server)

@@ -1065,6 +1076,12 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),

     }

 #endif

+  if (orig_dev)

+    {

+      dev = orig_dev;

+      orig_dev = 0;

+    }

+

   rc = grub_linuxefi_secure_validate((void *)(unsigned long)address, fsize);

   grub_dprintf ("chain", "linuxefi_secure_validate: %d\n", rc);

   if (rc > 0)

@@ -1087,6 +1104,12 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)),

   // -1 fall-through to fail

 fail:

+  if (orig_dev)

+    {

+      dev = orig_dev;

+      orig_dev = 0;

+    }

+

   if (dev)

     grub_device_close (dev);

diff --git a/include/grub/loopback.h b/include/grub/loopback.h

new file mode 100644

index 00000000000..3b9a9e32e80

--- /dev/null

+++ b/include/grub/loopback.h

@@ -0,0 +1,30 @@

+/*

+ *  GRUB  --  GRand Unified Bootloader

+ *  Copyright (C) 2019  Free Software Foundation, Inc.

+ *

+ *  GRUB is free software: you can redistribute it and/or modify

+ *  it under the terms of the GNU General Public License as published by

+ *  the Free Software Foundation, either version 3 of the License, or

+ *  (at your option) any later version.

+ *

+ *  GRUB is distributed in the hope that it will be useful,

+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of

+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+ *  GNU General Public License for more details.

+ *

+ *  You should have received a copy of the GNU General Public License

+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.

+ */

+

+#ifndef GRUB_LOOPBACK_HEADER

+#define GRUB_LOOPBACK_HEADER	1

+

+struct grub_loopback

+{

+  char *devname;

+  grub_file_t file;

+  struct grub_loopback *next;

+  unsigned long id;

+};

+

+#endif /* ! GRUB_LOOPBACK_HEADER */