af_key: Fix heap information leak

Since x->encap of pfkey_msg2xfrm_state() is not
initialized to 0, kernel heap data can be leaked.

Fix with kzalloc() to prevent this.
Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/key/af_key.c

@@ -1261,7 +1261,7 @@ static struct xfrm_state * pfkey_msg2xfrm_state(struct net *net,
 		const struct sadb_x_nat_t_type* n_type;
 		struct xfrm_encap_tmpl *natt;
 
-		x->encap = kmalloc(sizeof(*x->encap), GFP_KERNEL);
+		x->encap = kzalloc(sizeof(*x->encap), GFP_KERNEL);
 		if (!x->encap) {
 			err = -ENOMEM;
 			goto out;