Phonet: refuse to send bigger than MTU packets

Signed-off-by: Rémi Denis-Courmont <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/phonet/af_phonet.c

···
 	struct phonethdr *ph;
 	int err;
 
-	if (skb->len + 2 > 0xffff) {
-		/* Phonet length field would overflow */
+	if (skb->len + 2 > 0xffff /* Phonet length field limit */ ||
+	    skb->len + sizeof(struct phonethdr) > dev->mtu) {
 		err = -EMSGSIZE;
 		goto drop;
 	}