macsec: restrict to ethernet devices

Only attach macsec to ethernet devices.

Syzbot was able to trigger a KMSAN warning in macsec_handle_frame
by attaching to a phonet device.

Macvlan has a similar check in macvlan_port_create.

v1->v2
  - fix commit message typo
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macsec.c

@@ -19,6 +19,7 @@
 #include <net/gro_cells.h>
 #include <net/macsec.h>
 #include <linux/phy.h>
+#include <linux/if_arp.h>
 
 #include <uapi/linux/if_macsec.h>
 
@@ -3665,6 +3666,8 @@ static int macsec_newlink(struct net *net, struct net_device *dev,
 	real_dev = __dev_get_by_index(net, nla_get_u32(tb[IFLA_LINK]));
 	if (!real_dev)
 		return -ENODEV;
+	if (real_dev->type != ARPHRD_ETHER)
+		return -EINVAL;
 
 	dev->priv_flags |= IFF_MACSEC;