xfrm_user: verify policy direction at XFRM_MSG_POLEXPIRE handler

Add missing check for policy direction verification. This is
especially important since without this xfrm_user may end up
deleting per-socket policy which is not allowed.
Signed-off-by: NTimo Teras <timo.teras@iki.fi>
Acked-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/xfrm/xfrm_user.c

@@ -1741,6 +1741,10 @@ static int xfrm_add_pol_expire(struct sk_buff *skb, struct nlmsghdr *nlh,
 	if (err)
 		return err;
 
+	err = verify_policy_dir(p->dir);
+	if (err)
+		return err;
+
 	if (p->index)
 		xp = xfrm_policy_byid(net, mark, type, p->dir, p->index, 0, &err);
 	else {