diff --git a/mm/memory.c b/mm/memory.c
index f82b359b..51a8691 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -981,6 +981,8 @@
 	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.