diff --git a/net/netfilter/xt_quota2.c b/net/netfilter/xt_quota2.c
index 3d2ae4e..7f9d998 100644
--- a/net/netfilter/xt_quota2.c
+++ b/net/netfilter/xt_quota2.c
@@ -135,6 +135,8 @@
 	if (copy_from_user(buf, input, size) != 0)
 		return -EFAULT;
 	buf[sizeof(buf)-1] = '\0';
+	if (size < sizeof(buf))
+		buf[size] = '\0';
 
 	spin_lock_bh(&e->lock);
 	e->quota = simple_strtoull(buf, NULL, 0);