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: Timo Teras <timo.teras@iki.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 6106b72..da5ba86 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1741,6 +1741,10 @@
 	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 {