efi_loader: CloseProtocol() requires valid agent handle

Return EFI_INVALID_PARAMETER from CloseProtcol() if the agent handle is not
valid.

Return EFI_INVALID_PARAMETER if the optional controller handle is not
valid.

Return immediately from efi_search_obj if the handle is NULL.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
index 194df5a..967b39b 100644
--- a/lib/efi_loader/efi_boottime.c
+++ b/lib/efi_loader/efi_boottime.c
@@ -971,11 +971,13 @@
 {
 	struct efi_object *efiobj;
 
+	if (!handle)
+		return NULL;
+
 	list_for_each_entry(efiobj, &efi_obj_list, link) {
 		if (efiobj == handle)
 			return efiobj;
 	}
-
 	return NULL;
 }
 
@@ -1982,7 +1984,8 @@
 	EFI_ENTRY("%p, %pUl, %p, %p", handle, protocol, agent_handle,
 		  controller_handle);
 
-	if (!agent_handle) {
+	if (!efi_search_obj(agent_handle) ||
+	    (controller_handle && !efi_search_obj(controller_handle))) {
 		r = EFI_INVALID_PARAMETER;
 		goto out;
 	}