xfrm: clean up xfrm protocol checks

In commit 6a53b75932 ("xfrm: check id proto in validate_tmpl()")
I introduced a check for xfrm protocol, but according to Herbert
IPSEC_PROTO_ANY should only be used as a wildcard for lookup, so
it should be removed from validate_tmpl().

And, IPSEC_PROTO_ANY is expected to only match 3 IPSec-specific
protocols, this is why xfrm_state_flush() could still miss
IPPROTO_ROUTING, which leads that those entries are left in
net->xfrm.state_all before exit net. Fix this by replacing
IPSEC_PROTO_ANY with zero.

This patch also extracts the check from validate_tmpl() to
xfrm_id_proto_valid() and uses it in parse_ipsecrequest().
With this, no other protocols should be added into xfrm.

Fixes: 6a53b75932 ("xfrm: check id proto in validate_tmpl()")
Reported-by: syzbot+0bf0519d6e0de15914fe@syzkaller.appspotmail.com
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -1404,6 +1404,23 @@ static inline int xfrm_state_kern(const struct xfrm_state *x)
 	return atomic_read(&x->tunnel_users);
 }
 
+static inline bool xfrm_id_proto_valid(u8 proto)
+{
+	switch (proto) {
+	case IPPROTO_AH:
+	case IPPROTO_ESP:
+	case IPPROTO_COMP:
+#if IS_ENABLED(CONFIG_IPV6)
+	case IPPROTO_ROUTING:
+	case IPPROTO_DSTOPTS:
+#endif
+		return true;
+	default:
+		return false;
+	}
+}
+
+/* IPSEC_PROTO_ANY only matches 3 IPsec protocols, 0 could match all. */
 static inline int xfrm_id_proto_match(u8 proto, u8 userproto)
 {
 	return (!userproto || proto == userproto ||

net/ipv6/xfrm6_tunnel.c

@@ -345,7 +345,7 @@ static void __net_exit xfrm6_tunnel_net_exit(struct net *net)
 	unsigned int i;
 
 	xfrm_flush_gc();
-	xfrm_state_flush(net, IPSEC_PROTO_ANY, false, true);
+	xfrm_state_flush(net, 0, false, true);
 
 	for (i = 0; i < XFRM6_TUNNEL_SPI_BYADDR_HSIZE; i++)
 		WARN_ON_ONCE(!hlist_empty(&xfrm6_tn->spi_byaddr[i]));

net/key/af_key.c

@@ -1951,8 +1951,10 @@ parse_ipsecrequest(struct xfrm_policy *xp, struct sadb_x_ipsecrequest *rq)
 
 	if (rq->sadb_x_ipsecrequest_mode == 0)
 		return -EINVAL;
+	if (!xfrm_id_proto_valid(rq->sadb_x_ipsecrequest_proto))
+		return -EINVAL;
 
-	t->id.proto = rq->sadb_x_ipsecrequest_proto; /* XXX check proto */
+	t->id.proto = rq->sadb_x_ipsecrequest_proto;
 	if ((mode = pfkey_mode_to_xfrm(rq->sadb_x_ipsecrequest_mode)) < 0)
 		return -EINVAL;
 	t->mode = mode;

net/xfrm/xfrm_state.c

@@ -2384,7 +2384,7 @@ void xfrm_state_fini(struct net *net)
 
 	flush_work(&net->xfrm.state_hash_work);
 	flush_work(&xfrm_state_gc_work);
-	xfrm_state_flush(net, IPSEC_PROTO_ANY, false, true);
+	xfrm_state_flush(net, 0, false, true);
 
 	WARN_ON(!list_empty(&net->xfrm.state_all));
 

net/xfrm/xfrm_user.c

@@ -1513,20 +1513,8 @@ static int validate_tmpl(int nr, struct xfrm_user_tmpl *ut, u16 family)
 			return -EINVAL;
 		}
 
-		switch (ut[i].id.proto) {
+		if (!xfrm_id_proto_valid(ut[i].id.proto))
-		case IPPROTO_AH:
-		case IPPROTO_ESP:
-		case IPPROTO_COMP:
-#if IS_ENABLED(CONFIG_IPV6)
-		case IPPROTO_ROUTING:
-		case IPPROTO_DSTOPTS:
-#endif
-		case IPSEC_PROTO_ANY:
-			break;
-		default:
 			return -EINVAL;
-		}
-
 	}
 
 	return 0;