diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..717aa0e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@
 	int i;
 	unsigned int vm_flags;
 
+	if (len <= 0)
+		return 0;
 	/* 
 	 * Require read or write permissions.
 	 * If 'force' is set, we only require the "MAY" flags.