[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>

1 files changed, 12 insertions, 5 deletions

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index b4b478353b2..0e097ba14d7 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -2410,20 +2410,27 @@ static struct file_operations neigh_stat_seq_fops = {
 #endif /* CONFIG_PROC_FS */
 
 #ifdef CONFIG_ARPD
+static inline size_t neigh_nlmsg_size(void)
+{
+        return NLMSG_ALIGN(sizeof(struct ndmsg))
+               + nla_total_size(MAX_ADDR_LEN) /* NDA_DST */
+               + nla_total_size(MAX_ADDR_LEN) /* NDA_LLADDR */
+               + nla_total_size(sizeof(struct nda_cacheinfo))
+               + nla_total_size(4); /* NDA_PROBES */
+}
+
 static void __neigh_notify(struct neighbour *n, int type, int flags)
 {
         struct sk_buff *skb;
         int err = -ENOBUFS;
 
-        skb = nlmsg_new(NLMSG_GOODSIZE, GFP_ATOMIC);
+        skb = nlmsg_new(neigh_nlmsg_size(), GFP_ATOMIC);
         if (skb == NULL)
                 goto errout;
 
         err = neigh_fill_info(skb, n, 0, 0, type, flags);
-        if (err < 0) {
-                kfree_skb(skb);
-                goto errout;
-        }
+        /* failure implies BUG in neigh_nlmsg_size() */
+        BUG_ON(err < 0);
 
         err = rtnl_notify(skb, 0, RTNLGRP_NEIGH, NULL, GFP_ATOMIC);
 errout: