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>

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) {
-		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:
+		if (!xfrm_id_proto_valid(ut[i].id.proto))
 			return -EINVAL;
-		}
-
 	}
 
 	return 0;