net: Check for presence of IFLA_AF_SPEC

ndo_bridge_setlink() is currently only called on the slave if
IFLA_AF_SPEC is set but this is a very fragile assumption and may
change in the future.

Cc: Ajit Khaparde <ajit.khaparde@emulex.com>
Cc: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/emulex/benet/be_main.c

@@ -4309,6 +4309,8 @@ static int be_ndo_bridge_setlink(struct net_device *dev, struct nlmsghdr *nlh)
 		return -EOPNOTSUPP;
 
 	br_spec = nlmsg_find_attr(nlh, sizeof(struct ifinfomsg), IFLA_AF_SPEC);
+	if (!br_spec)
+		return -EINVAL;
 
 	nla_for_each_nested(attr, br_spec, rem) {
 		if (nla_type(attr) != IFLA_BRIDGE_MODE)

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -7669,6 +7669,8 @@ static int ixgbe_ndo_bridge_setlink(struct net_device *dev,
 		return -EOPNOTSUPP;
 
 	br_spec = nlmsg_find_attr(nlh, sizeof(struct ifinfomsg), IFLA_AF_SPEC);
+	if (!br_spec)
+		return -EINVAL;
 
 	nla_for_each_nested(attr, br_spec, rem) {
 		__u16 mode;