Index: VirtualBox-6.1.28/include/iprt/stdarg.h
===================================================================
--- VirtualBox-6.1.28.orig/include/iprt/stdarg.h
+++ VirtualBox-6.1.28/include/iprt/stdarg.h
@@ -51,7 +51,12 @@
# include <stdarg.h>
# endif
# else
-# include <stdarg.h>
+# include <linux/version.h>
+# if LINUX_VERSION_CODE < KERNEL_VERSION(5, 15, 0)
+# include <stdarg.h>
+# else
+# include <linux/stdarg.h>
+# endif
#endif