rtnetlink: fix rtnl_vfinfo_size

commit 7e75f74a upstream.

The size reported by rtnl_vfinfo_size doesn't match the space used by
rtnl_fill_vfinfo.

rtnl_vfinfo_size currently doesn't account for the nest attributes
used by statistics (added in commit 3b766cd8), nor for struct
ifla_vf_tx_rate (since commit ed616689, which added ifla_vf_rate
to the dump without removing ifla_vf_tx_rate, but replaced
ifla_vf_tx_rate with ifla_vf_rate in the size computation).

Fixes: 3b766cd8 ("net/core: Add reading VF statistics through the PF netdevice")
Fixes: ed616689 ("net-next:v4: Add support to configure SR-IOV VF minimum and maximum Tx rate through ip tool")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.16: only need to add space for IFLA_VF_TX_RATE]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/core/rtnetlink.c

@@ -794,12 +794,13 @@ static inline int rtnl_vfinfo_size(const struct net_device *dev,
 	if (dev->dev.parent && dev_is_pci(dev->dev.parent) &&
 	    (ext_filter_mask & RTEXT_FILTER_VF)) {
 		int num_vfs = dev_num_vf(dev->dev.parent);
-		size_t size = nla_total_size(sizeof(struct nlattr));
-		size += nla_total_size(num_vfs * sizeof(struct nlattr));
+		size_t size = nla_total_size(0);
 		size += num_vfs *
-			(nla_total_size(sizeof(struct ifla_vf_mac)) +
+			(nla_total_size(0) +
+			 nla_total_size(sizeof(struct ifla_vf_mac)) +
 			 nla_total_size(sizeof(struct ifla_vf_vlan)) +
 			 nla_total_size(sizeof(struct ifla_vf_spoofchk)) +
+			 nla_total_size(sizeof(struct ifla_vf_tx_rate)) +
 			 nla_total_size(sizeof(struct ifla_vf_rate)) +
 			 nla_total_size(sizeof(struct ifla_vf_link_state)));
 		return size;