[NETLINK]: Do precise netlink message allocations where possible

Account for the netlink message header size directly in nlmsg_new()
instead of relying on the caller calculate it correctly.

Replaces error handling of message construction functions when
constructing notifications with bug traps since a failure implies
a bug in calculating the size of the skb.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 7 insertions, 4 deletions

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 66411622e06e..e61e1e138421 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -174,6 +174,7 @@ int netlink_sendskb(struct sock *sk, struct sk_buff *skb, int protocol);
  */
 #define NLMSG_GOODORDER 0
 #define NLMSG_GOODSIZE (SKB_MAX_ORDER(0, NLMSG_GOODORDER))
+#define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
 
 
 struct netlink_callback
diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index e4ba781d289f..bc3c26494c3d 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -52,6 +52,7 @@ struct fib_rules_ops
                                         struct nlmsghdr *,
                                         struct fib_rule_hdr *);
         u32                     (*default_pref)(void);
+        size_t                  (*nlmsg_payload)(struct fib_rule *);
 
         int                     nlgroup;
         struct nla_policy       *policy;
diff --git a/include/net/netlink.h b/include/net/netlink.h
index ce5cba19c393..30021339157c 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -500,14 +500,15 @@ static inline struct nlmsghdr *nlmsg_put_answer(struct sk_buff *skb,
 
 /**
  * nlmsg_new - Allocate a new netlink message
- * @size: maximum size of message
+ * @payload: size of the message payload
  * @flags: the type of memory to allocate.
  *
- * Use NLMSG_GOODSIZE if size isn't know and you need a good default size.
+ * Use NLMSG_DEFAULT_SIZE if the size of the payload isn't known
+ * and a good default is needed.
  */
-static inline struct sk_buff *nlmsg_new(int size, gfp_t flags)
+static inline struct sk_buff *nlmsg_new(size_t payload, gfp_t flags)
 {
-        return alloc_skb(size, flags);
+        return alloc_skb(nlmsg_total_size(payload), flags);
 }
 
 /**