rtnetlink: count IFLA_INFO_SLAVE_KIND in if_nlmsg_size

rtnl_link_get_slave_info_data_size counts IFLA_INFO_SLAVE_DATA, but
rtnl_link_slave_info_fill adds both IFLA_INFO_SLAVE_DATA and
IFLA_INFO_SLAVE_KIND.

Fixes: ba7d49b ("rtnetlink: provide api for getting and setting slave info")
Reviewed-by: Jiri Pirko <[email protected]>
Signed-off-by: Sabrina Dubroca <[email protected]>
Link: https://patch.msgid.link/049843b532e23cde7ddba263c0bbe35ba6f0d26d.1773919462.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <[email protected]>

Author: qsn

net/core/rtnetlink.c

@@ -707,11 +707,14 @@ static size_t rtnl_link_get_slave_info_data_size(const struct net_device *dev)
 		goto out;
 
 	ops = master_dev->rtnl_link_ops;
-	if (!ops || !ops->get_slave_size)
+	if (!ops)
+		goto out;
+	size += nla_total_size(strlen(ops->kind) + 1);  /* IFLA_INFO_SLAVE_KIND */
+	if (!ops->get_slave_size)
 		goto out;
 	/* IFLA_INFO_SLAVE_DATA + nested data */
-	size = nla_total_size(sizeof(struct nlattr)) +
-	       ops->get_slave_size(master_dev, dev);
+	size += nla_total_size(sizeof(struct nlattr)) +
+		ops->get_slave_size(master_dev, dev);
 
 out:
 	rcu_read_unlock();