From 9dca459bf3d81d0a5ddcba6fa15b1ff5d48eddc7 Mon Sep 17 00:00:00 2001
From: Julian Andres Klode <julian.klode@canonical.com>
Date: Wed, 4 Aug 2021 10:43:30 +0200
Subject: [PATCH] Extract is_removable_media_path() out of
 should_use_fallback()

Simple refactoring that extracts the path checking on the given
loaded image. This will be useful to check if we were booted via
removable media path in other places.
---
 shim.c | 48 +++++++++++++++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 17 deletions(-)

diff --git a/shim.c b/shim.c
index 1e95e6df1..2bc77b0d3 100644
--- a/shim.c
+++ b/shim.c
@@ -690,25 +690,12 @@ verify_buffer (char *data, int datasize,
 }
 
 static int
-should_use_fallback(EFI_HANDLE image_handle)
+is_removable_media_path(EFI_LOADED_IMAGE *li)
 {
-	EFI_LOADED_IMAGE *li;
 	unsigned int pathlen = 0;
 	CHAR16 *bootpath = NULL;
-	EFI_FILE_IO_INTERFACE *fio = NULL;
-	EFI_FILE *vh = NULL;
-	EFI_FILE *fh = NULL;
-	EFI_STATUS efi_status;
 	int ret = 0;
 
-	efi_status = BS->HandleProtocol(image_handle, &EFI_LOADED_IMAGE_GUID,
-					(void **)&li);
-	if (EFI_ERROR(efi_status)) {
-		perror(L"Could not get image for boot" EFI_ARCH L".efi: %r\n",
-		       efi_status);
-		return 0;
-	}
-
 	bootpath = DevicePathToStr(li->FilePath);
 
 	/* Check the beginning of the string and the end, to avoid
@@ -726,6 +713,36 @@ should_use_fallback(EFI_HANDLE image_handle)
 	if (pathlen < 5 || StrCaseCmp(bootpath + pathlen - 4, L".EFI"))
 		goto error;
 
+	ret = 1;
+
+error:
+	if (bootpath)
+		FreePool(bootpath);
+
+	return ret;
+}
+
+static int
+should_use_fallback(EFI_HANDLE image_handle)
+{
+	EFI_LOADED_IMAGE *li;
+	EFI_FILE_IO_INTERFACE *fio = NULL;
+	EFI_FILE *vh = NULL;
+	EFI_FILE *fh = NULL;
+	EFI_STATUS efi_status;
+	int ret = 0;
+
+	efi_status = BS->HandleProtocol(image_handle, &EFI_LOADED_IMAGE_GUID,
+	                                (void **)&li);
+	if (EFI_ERROR(efi_status)) {
+		perror(L"Could not get image for boot" EFI_ARCH L".efi: %r\n",
+		       efi_status);
+		return 0;
+	}
+
+	if (!is_removable_media_path(li))
+		goto error;
+
 	efi_status = BS->HandleProtocol(li->DeviceHandle, &FileSystemProtocol,
 					(void **) &fio);
 	if (EFI_ERROR(efi_status)) {
@@ -758,12 +775,9 @@ should_use_fallback(EFI_HANDLE image_handle)
 		fh->Close(fh);
 	if (vh)
 		vh->Close(vh);
-	if (bootpath)
-		FreePool(bootpath);
 
 	return ret;
 }
-
 /*
  * Open the second stage bootloader and read it into a buffer
  */