[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, 26 insertions, 13 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 02f3c7947898..50d6cb40c6e3 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -273,6 +273,25 @@ static void copy_rtnl_link_stats(struct rtnl_link_stats *a,
         a->tx_compressed = b->tx_compressed;
 };
 
+static inline size_t if_nlmsg_size(int iwbuflen)
+{
+        return NLMSG_ALIGN(sizeof(struct ifinfomsg))
+               + nla_total_size(IFNAMSIZ) /* IFLA_IFNAME */
+               + nla_total_size(IFNAMSIZ) /* IFLA_QDISC */
+               + nla_total_size(sizeof(struct rtnl_link_ifmap))
+               + nla_total_size(sizeof(struct rtnl_link_stats))
+               + nla_total_size(MAX_ADDR_LEN) /* IFLA_ADDRESS */
+               + nla_total_size(MAX_ADDR_LEN) /* IFLA_BROADCAST */
+               + nla_total_size(4) /* IFLA_TXQLEN */
+               + nla_total_size(4) /* IFLA_WEIGHT */
+               + nla_total_size(4) /* IFLA_MTU */
+               + nla_total_size(4) /* IFLA_LINK */
+               + nla_total_size(4) /* IFLA_MASTER */
+               + nla_total_size(1) /* IFLA_OPERSTATE */
+               + nla_total_size(1) /* IFLA_LINKMODE */
+               + nla_total_size(iwbuflen);
+}
+
 static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
                             void *iwbuf, int iwbuflen, int type, u32 pid,
                             u32 seq, u32 change, unsigned int flags)
@@ -558,7 +577,7 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
         struct sk_buff *nskb;
         char *iw_buf = NULL, *iw = NULL;
         int iw_buf_len = 0;
-        int err, payload;
+        int err;
 
         err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFLA_MAX, ifla_policy);
         if (err < 0)
@@ -587,9 +606,7 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
         }
 #endif  /* CONFIG_NET_WIRELESS_RTNETLINK */
 
-        payload = NLMSG_ALIGN(sizeof(struct ifinfomsg) +
-                              nla_total_size(iw_buf_len));
-        nskb = nlmsg_new(nlmsg_total_size(payload), GFP_KERNEL);
+        nskb = nlmsg_new(if_nlmsg_size(iw_buf_len), GFP_KERNEL);
         if (nskb == NULL) {
                 err = -ENOBUFS;
                 goto errout;
@@ -597,10 +614,8 @@ static int rtnl_getlink(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
 
         err = rtnl_fill_ifinfo(nskb, dev, iw, iw_buf_len, RTM_NEWLINK,
                                NETLINK_CB(skb).pid, nlh->nlmsg_seq, 0, 0);
-        if (err <= 0) {
-                kfree_skb(nskb);
-                goto errout;
-        }
+        /* failure impilies BUG in if_nlmsg_size or wireless_rtnetlink_get */
+        BUG_ON(err < 0);
 
         err = rtnl_unicast(nskb, NETLINK_CB(skb).pid);
 errout:
@@ -639,15 +654,13 @@ void rtmsg_ifinfo(int type, struct net_device *dev, unsigned change)
         struct sk_buff *skb;
         int err = -ENOBUFS;
 
-        skb = nlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+        skb = nlmsg_new(if_nlmsg_size(0), GFP_KERNEL);
         if (skb == NULL)
                 goto errout;
 
         err = rtnl_fill_ifinfo(skb, dev, NULL, 0, type, 0, 0, change, 0);
-        if (err < 0) {
-                kfree_skb(skb);
-                goto errout;
-        }
+        /* failure implies BUG in if_nlmsg_size() */
+        BUG_ON(err < 0);
 
         err = rtnl_notify(skb, 0, RTNLGRP_LINK, NULL, GFP_KERNEL);
 errout: