test_firmware: Test platform fw loading on non-EFI systems

On non-EFI systems, it wasn't possible to test the platform firmware
loader because it will have never set "checked_fw" during __init.
Instead, allow the test code to override this check. Additionally split
the declarations into a private header file so it there is greater
enforcement of the symbol visibility.

Fixes: 548193c ("test_firmware: add support for firmware_request_platform")
Cc: stable@vger.kernel.org
Acked-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200724213640.389191-2-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firmware/efi/embedded-firmware.c

@@ -14,11 +14,22 @@
 #include <linux/vmalloc.h>
 #include <crypto/sha.h>
 
+#include "embedded-firmware.h"
+
+#ifdef CONFIG_TEST_FIRMWARE
+# define EFI_EMBEDDED_FW_VISIBILITY
+#else
+# define EFI_EMBEDDED_FW_VISIBILITY static
+#endif
+
+EFI_EMBEDDED_FW_VISIBILITY LIST_HEAD(efi_embedded_fw_list);
+EFI_EMBEDDED_FW_VISIBILITY bool efi_embedded_fw_checked;
+
 /* Exported for use by lib/test_firmware.c only */
-LIST_HEAD(efi_embedded_fw_list);
+#ifdef CONFIG_TEST_FIRMWARE
 EXPORT_SYMBOL_GPL(efi_embedded_fw_list);
-
-static bool checked_for_fw;
+EXPORT_SYMBOL_GPL(efi_embedded_fw_checked);
+#endif
 
 static const struct dmi_system_id * const embedded_fw_table[] = {
 #ifdef CONFIG_TOUCHSCREEN_DMI
@@ -119,14 +130,14 @@ void __init efi_check_for_embedded_firmwares(void)
 		}
 	}
 
-	checked_for_fw = true;
+	efi_embedded_fw_checked = true;
 }
 
 int efi_get_embedded_fw(const char *name, const u8 **data, size_t *size)
 {
 	struct efi_embedded_fw *iter, *fw = NULL;
 
-	if (!checked_for_fw) {
+	if (!efi_embedded_fw_checked) {
 		pr_warn("Warning %s called while we did not check for embedded fw\n",
 			__func__);
 		return -ENOENT;

drivers/firmware/efi/embedded-firmware.h

@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _EFI_EMBEDDED_FW_INTERNAL_H_
+#define _EFI_EMBEDDED_FW_INTERNAL_H_
+
+/*
+ * This struct and efi_embedded_fw_list are private to the efi-embedded fw
+ * implementation they only in separate header for use by lib/test_firmware.c.
+ */
+struct efi_embedded_fw {
+	struct list_head list;
+	const char *name;
+	const u8 *data;
+	size_t length;
+};
+
+extern struct list_head efi_embedded_fw_list;
+extern bool efi_embedded_fw_checked;
+
+#endif /* _EFI_EMBEDDED_FW_INTERNAL_H_ */

include/linux/efi_embedded_fw.h

@@ -7,19 +7,6 @@
 
 #define EFI_EMBEDDED_FW_PREFIX_LEN		8
 
-/*
- * This struct and efi_embedded_fw_list are private to the efi-embedded fw
- * implementation they are in this header for use by lib/test_firmware.c only!
- */
-struct efi_embedded_fw {
-	struct list_head list;
-	const char *name;
-	const u8 *data;
-	size_t length;
-};
-
-extern struct list_head efi_embedded_fw_list;
-
 /**
  * struct efi_embedded_fw_desc - This struct is used by the EFI embedded-fw
  *                               code to search for embedded firmwares.

lib/test_firmware.c

@@ -489,6 +489,7 @@ static ssize_t trigger_request_store(struct device *dev,
 static DEVICE_ATTR_WO(trigger_request);
 
 #ifdef CONFIG_EFI_EMBEDDED_FIRMWARE
+#include "../drivers/firmware/efi/embedded-firmware.h"
 static ssize_t trigger_request_platform_store(struct device *dev,
 					      struct device_attribute *attr,
 					      const char *buf, size_t count)
@@ -501,6 +502,7 @@ static ssize_t trigger_request_platform_store(struct device *dev,
 	};
 	struct efi_embedded_fw efi_embedded_fw;
 	const struct firmware *firmware = NULL;
+	bool saved_efi_embedded_fw_checked;
 	char *name;
 	int rc;
 
@@ -513,6 +515,8 @@ static ssize_t trigger_request_platform_store(struct device *dev,
 	efi_embedded_fw.data = (void *)test_data;
 	efi_embedded_fw.length = sizeof(test_data);
 	list_add(&efi_embedded_fw.list, &efi_embedded_fw_list);
+	saved_efi_embedded_fw_checked = efi_embedded_fw_checked;
+	efi_embedded_fw_checked = true;
 
 	pr_info("loading '%s'\n", name);
 	rc = firmware_request_platform(&firmware, name, dev);
@@ -530,6 +534,7 @@ static ssize_t trigger_request_platform_store(struct device *dev,
 	rc = count;
 
 out:
+	efi_embedded_fw_checked = saved_efi_embedded_fw_checked;
 	release_firmware(firmware);
 	list_del(&efi_embedded_fw.list);
 	kfree(name);