Merge branch 'rtnetlink-avoid-a-warning-in-rtnl_newlink'

Jakub Kicinski says:

====================
rtnetlink: avoid a warning in rtnl_newlink()

I've been hoping for some time that someone more competent would fix
the stack frame size warning in rtnl_newlink(), but looks like I'll
have to take a stab at it myself :)  That's the only warning I see
in most of my builds.

First patch refactors away a somewhat surprising if (1) code block.
Reindentation will most likely cause cherry-pick problems but OTOH
rtnl_newlink() doesn't seem to be changed often, so perhaps we can
risk it in the name of cleaner code?

Second patch fixes the warning in simplest possible way.  I was
pondering if there is any more clever solution, but I can't see it..
rtnl_newlink() is quite long with a lot of possible execution paths
so doing memory allocations half way through leads to very ugly
results.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -2971,20 +2971,24 @@ static int rtnl_group_changelink(const struct sk_buff *skb,
 	return 0;
 }
 
-static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
-			struct netlink_ext_ack *extack)
+static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
+			  struct nlattr **attr, struct netlink_ext_ack *extack)
 {
+	struct nlattr *slave_attr[RTNL_SLAVE_MAX_TYPE + 1];
+	unsigned char name_assign_type = NET_NAME_USER;
+	struct nlattr *linkinfo[IFLA_INFO_MAX + 1];
+	const struct rtnl_link_ops *m_ops = NULL;
+	struct net_device *master_dev = NULL;
 	struct net *net = sock_net(skb->sk);
 	const struct rtnl_link_ops *ops;
-	const struct rtnl_link_ops *m_ops = NULL;
+	struct nlattr *tb[IFLA_MAX + 1];
+	struct net *dest_net, *link_net;
+	struct nlattr **slave_data;
+	char kind[MODULE_NAME_LEN];
 	struct net_device *dev;
-	struct net_device *master_dev = NULL;
 	struct ifinfomsg *ifm;
-	char kind[MODULE_NAME_LEN];
 	char ifname[IFNAMSIZ];
-	struct nlattr *tb[IFLA_MAX+1];
-	struct nlattr *linkinfo[IFLA_INFO_MAX+1];
-	unsigned char name_assign_type = NET_NAME_USER;
+	struct nlattr **data;
 	int err;
 
 #ifdef CONFIG_MODULES
@@ -3040,13 +3044,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 		ops = NULL;
 	}
 
-	if (1) {
-		struct nlattr *attr[RTNL_MAX_TYPE + 1];
-		struct nlattr *slave_attr[RTNL_SLAVE_MAX_TYPE + 1];
-		struct nlattr **data = NULL;
-		struct nlattr **slave_data = NULL;
-		struct net *dest_net, *link_net = NULL;
-
+	data = NULL;
 	if (ops) {
 		if (ops->maxtype > RTNL_MAX_TYPE)
 			return -EINVAL;
@@ -3066,17 +3064,16 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 		}
 	}
 
+	slave_data = NULL;
 	if (m_ops) {
 		if (m_ops->slave_maxtype > RTNL_SLAVE_MAX_TYPE)
 			return -EINVAL;
 
 		if (m_ops->slave_maxtype &&
 		    linkinfo[IFLA_INFO_SLAVE_DATA]) {
-				err = nla_parse_nested(slave_attr,
-						       m_ops->slave_maxtype,
+			err = nla_parse_nested(slave_attr, m_ops->slave_maxtype,
 					       linkinfo[IFLA_INFO_SLAVE_DATA],
-						       m_ops->slave_policy,
-						       extack);
+					       m_ops->slave_policy, extack);
 			if (err < 0)
 				return err;
 			slave_data = slave_attr;
@@ -3106,16 +3103,14 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			if (!m_ops || !m_ops->slave_changelink)
 				return -EOPNOTSUPP;
 
-				err = m_ops->slave_changelink(master_dev, dev,
-							      tb, slave_data,
-							      extack);
+			err = m_ops->slave_changelink(master_dev, dev, tb,
+						      slave_data, extack);
 			if (err < 0)
 				return err;
 			status |= DO_SETLINK_NOTIFY;
 		}
 
-			return do_setlink(skb, dev, ifm, extack, tb, ifname,
-					  status);
+		return do_setlink(skb, dev, ifm, extack, tb, ifname, status);
 	}
 
 	if (!(nlh->nlmsg_flags & NLM_F_CREATE)) {
@@ -3168,6 +3163,8 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 		err = -EPERM;
 		if (!netlink_ns_capable(skb, link_net->user_ns, CAP_NET_ADMIN))
 			goto out;
+	} else {
+		link_net = NULL;
 	}
 
 	dev = rtnl_create_link(link_net ? : dest_net, ifname,
@@ -3180,8 +3177,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 	dev->ifindex = ifm->ifi_index;
 
 	if (ops->newlink) {
-			err = ops->newlink(link_net ? : net, dev, tb, data,
-					   extack);
+		err = ops->newlink(link_net ? : net, dev, tb, data, extack);
 		/* Drivers should call free_netdev() in ->destructor
 		 * and unregister it on failure after registration
 		 * so that device could be finally freed in rtnl_unlock.
@@ -3208,8 +3204,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 			goto out_unregister;
 	}
 	if (tb[IFLA_MASTER]) {
-			err = do_set_master(dev, nla_get_u32(tb[IFLA_MASTER]),
-					    extack);
+		err = do_set_master(dev, nla_get_u32(tb[IFLA_MASTER]), extack);
 		if (err)
 			goto out_unregister;
 	}
@@ -3228,7 +3223,21 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
 		unregister_netdevice(dev);
 	}
 	goto out;
-	}
+}
+
+static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
+			struct netlink_ext_ack *extack)
+{
+	struct nlattr **attr;
+	int ret;
+
+	attr = kmalloc_array(RTNL_MAX_TYPE + 1, sizeof(*attr), GFP_KERNEL);
+	if (!attr)
+		return -ENOMEM;
+
+	ret = __rtnl_newlink(skb, nlh, attr, extack);
+	kfree(attr);
+	return ret;
 }
 
 static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr *nlh,