[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, 13 insertions, 5 deletions

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 7602c79a389b..f38cbbae0ae3 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1120,6 +1120,16 @@ static struct notifier_block ip_netdev_notifier = {
         .notifier_call =inetdev_event,
 };
 
+static inline size_t inet_nlmsg_size(void)
+{
+        return NLMSG_ALIGN(sizeof(struct ifaddrmsg))
+               + nla_total_size(4) /* IFA_ADDRESS */
+               + nla_total_size(4) /* IFA_LOCAL */
+               + nla_total_size(4) /* IFA_BROADCAST */
+               + nla_total_size(4) /* IFA_ANYCAST */
+               + nla_total_size(IFNAMSIZ); /* IFA_LABEL */
+}
+
 static int inet_fill_ifaddr(struct sk_buff *skb, struct in_ifaddr *ifa,
                             u32 pid, u32 seq, int event, unsigned int flags)
 {
@@ -1208,15 +1218,13 @@ static void rtmsg_ifa(int event, struct in_ifaddr* ifa, struct nlmsghdr *nlh,
         u32 seq = nlh ? nlh->nlmsg_seq : 0;
         int err = -ENOBUFS;
 
-        skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+        skb = nlmsg_new(inet_nlmsg_size(), GFP_KERNEL);
         if (skb == NULL)
                 goto errout;
 
         err = inet_fill_ifaddr(skb, ifa, pid, seq, event, 0);
-        if (err < 0) {
-                kfree_skb(skb);
-                goto errout;
-        }
+        /* failure implies BUG in inet_nlmsg_size() */
+        BUG_ON(err < 0);
 
         err = rtnl_notify(skb, pid, RTNLGRP_IPV4_IFADDR, nlh, GFP_KERNEL);
 errout: