[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, 17 insertions, 6 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 0ad07c9087a7..a6472cb9054c 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2006,6 +2006,20 @@ int inet6_rtm_newroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
         return ip6_route_add(&cfg);
 }
 
+static inline size_t rt6_nlmsg_size(void)
+{
+        return NLMSG_ALIGN(sizeof(struct rtmsg))
+               + nla_total_size(16) /* RTA_SRC */
+               + nla_total_size(16) /* RTA_DST */
+               + nla_total_size(16) /* RTA_GATEWAY */
+               + nla_total_size(16) /* RTA_PREFSRC */
+               + nla_total_size(4) /* RTA_TABLE */
+               + nla_total_size(4) /* RTA_IIF */
+               + nla_total_size(4) /* RTA_OIF */
+               + nla_total_size(4) /* RTA_PRIORITY */
+               + nla_total_size(sizeof(struct rta_cacheinfo));
+}
+
 static int rt6_fill_node(struct sk_buff *skb, struct rt6_info *rt,
                          struct in6_addr *dst, struct in6_addr *src,
                          int iif, int type, u32 pid, u32 seq,
@@ -2200,7 +2214,6 @@ void inet6_rt_notify(int event, struct rt6_info *rt, struct nl_info *info)
         struct sk_buff *skb;
         u32 pid = 0, seq = 0;
         struct nlmsghdr *nlh = NULL;
-        int payload = sizeof(struct rtmsg) + 256;
         int err = -ENOBUFS;
 
         if (info) {
@@ -2210,15 +2223,13 @@ void inet6_rt_notify(int event, struct rt6_info *rt, struct nl_info *info)
                         seq = nlh->nlmsg_seq;
         }
 
-        skb = nlmsg_new(nlmsg_total_size(payload), gfp_any());
+        skb = nlmsg_new(rt6_nlmsg_size(), gfp_any());
         if (skb == NULL)
                 goto errout;
 
         err = rt6_fill_node(skb, rt, NULL, NULL, 0, event, pid, seq, 0, 0);
-        if (err < 0) {
-                kfree_skb(skb);
-                goto errout;
-        }
+        /* failure implies BUG in rt6_nlmsg_size() */
+        BUG_ON(err < 0);
 
         err = rtnl_notify(skb, pid, RTNLGRP_IPV6_ROUTE, nlh, gfp_any());
 errout: