net: Validate IFLA_BRIDGE_MODE attribute length

Payload is currently accessed blindly and may exceed valid message
boundaries.

Fixes: a77dcb8c8 ("be2net: set and query VEB/VEPA mode of the PF interface")
Fixes: 815cccbf1 ("ixgbe: add setlink, getlink support to ixgbe and ixgbevf")
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>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -7677,6 +7677,9 @@ static int ixgbe_ndo_bridge_setlink(struct net_device *dev,
 		if (nla_type(attr) != IFLA_BRIDGE_MODE)
 			continue;
 
+		if (nla_len(attr) < sizeof(mode))
+			return -EINVAL;
+
 		mode = nla_get_u16(attr);
 		if (mode == BRIDGE_MODE_VEPA) {
 			reg = 0;