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From a5c5bcf1ac7b0057496b10a030fe1d9d24eb2775 Mon Sep 17 00:00:00 2001
From: Chris Coulson <chris.coulson@canonical.com>
Date: Wed, 22 Jul 2020 17:06:04 +0100
Subject: [PATCH 322/336] Fix a regression caused by "efi: fix some malformed
device path arithmetic errors"
This commit introduced a bogus check inside copy_file_path to
determine whether the destination grub_efi_file_path_device_path_t
was valid before anything was copied to it. Depending on the
contents of the heap buffer, this check could fail which would
result in copy_file_path returning early.
Without any error propagated to the caller, make_file_path would
then try to advance the invalid device path node with
GRUB_EFI_NEXT_DEVICE_PATH, which would also fail, returning a NULL
pointer that would subsequently be dereferenced.
Remove the bogus check, and also propagate errors from copy_file_path.
---
grub-core/loader/efi/chainloader.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c
index b90dfd6c5a6..dbcdf333b62 100644
--- a/grub-core/loader/efi/chainloader.c
+++ b/grub-core/loader/efi/chainloader.c
@@ -115,7 +115,7 @@ grub_chainloader_boot (void)
return grub_errno;
}
-static void
+static grub_err_t
copy_file_path (grub_efi_file_path_device_path_t *fp,
const char *str, grub_efi_uint16_t len)
{
@@ -125,15 +125,9 @@ copy_file_path (grub_efi_file_path_device_path_t *fp,
fp->header.type = GRUB_EFI_MEDIA_DEVICE_PATH_TYPE;
fp->header.subtype = GRUB_EFI_FILE_PATH_DEVICE_PATH_SUBTYPE;
- if (!GRUB_EFI_DEVICE_PATH_VALID ((grub_efi_device_path_t *)fp))
- {
- grub_error (GRUB_ERR_BAD_ARGUMENT, "EFI Device Path is invalid");
- return;
- }
-
path_name = grub_calloc (len, GRUB_MAX_UTF16_PER_UTF8 * sizeof (*path_name));
if (!path_name)
- return;
+ return grub_error (GRUB_ERR_OUT_OF_MEMORY, "failed to allocate path buffer");
size = grub_utf8_to_utf16 (path_name, len * GRUB_MAX_UTF16_PER_UTF8,
(const grub_uint8_t *) str, len, 0);
@@ -145,6 +139,8 @@ copy_file_path (grub_efi_file_path_device_path_t *fp,
/* File Path is NULL terminated */
fp->path_name[size++] = '\0';
fp->header.length = size * sizeof (grub_efi_char16_t) + sizeof (*fp);
+ grub_free (path_name);
+ return GRUB_ERR_NONE;
}
static grub_efi_device_path_t *
@@ -202,13 +198,19 @@ make_file_path (grub_efi_device_path_t *dp, const char *filename)
/* Fill the file path for the directory. */
d = (grub_efi_device_path_t *) ((char *) file_path
+ ((char *) d - (char *) dp));
- copy_file_path ((grub_efi_file_path_device_path_t *) d,
- dir_start, dir_end - dir_start);
+ if (copy_file_path ((grub_efi_file_path_device_path_t *) d,
+ dir_start, dir_end - dir_start) != GRUB_ERR_NONE)
+ {
+ fail:
+ grub_free (file_path);
+ return 0;
+ }
/* Fill the file path for the file. */
d = GRUB_EFI_NEXT_DEVICE_PATH (d);
- copy_file_path ((grub_efi_file_path_device_path_t *) d,
- dir_end + 1, grub_strlen (dir_end + 1));
+ if (copy_file_path ((grub_efi_file_path_device_path_t *) d,
+ dir_end + 1, grub_strlen (dir_end + 1)) != GRUB_ERR_NONE)
+ goto fail;
/* Fill the end of device path nodes. */
d = GRUB_EFI_NEXT_DEVICE_PATH (d);
--
2.26.2