udp: check encap socket in __udp_lib_err

Commit d26796ae5894 ("udp: check udp sock encap_type in __udp_lib_err")
added checks for encapsulated sockets but it broke cases when there is
no implementation of encap_err_lookup for encapsulation, i.e. ESP in
UDP encapsulation. Fix it by calling encap_err_lookup only if socket
implements this method otherwise treat it as legal socket.

Fixes: d26796ae5894 ("udp: check udp sock encap_type in __udp_lib_err")
Signed-off-by: Vadim Fedorenko <vfedorenko@novek.ru>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 6 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 62cd4cd52e84..1a742b710e54 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -645,10 +645,12 @@ static struct sock *__udp4_lib_err_encap(struct net *net,
 					 const struct iphdr *iph,
 					 struct udphdr *uh,
 					 struct udp_table *udptable,
+					 struct sock *sk,
 					 struct sk_buff *skb, u32 info)
 {
+	int (*lookup)(struct sock *sk, struct sk_buff *skb);
 	int network_offset, transport_offset;
-	struct sock *sk;
+	struct udp_sock *up;
 
 	network_offset = skb_network_offset(skb);
 	transport_offset = skb_transport_offset(skb);
@@ -659,18 +661,28 @@ static struct sock *__udp4_lib_err_encap(struct net *net,
 	/* Transport header needs to point to the UDP header */
 	skb_set_transport_header(skb, iph->ihl << 2);
 
+	if (sk) {
+		up = udp_sk(sk);
+
+		lookup = READ_ONCE(up->encap_err_lookup);
+		if (lookup && lookup(sk, skb))
+			sk = NULL;
+
+		goto out;
+	}
+
 	sk = __udp4_lib_lookup(net, iph->daddr, uh->source,
 			       iph->saddr, uh->dest, skb->dev->ifindex, 0,
 			       udptable, NULL);
 	if (sk) {
-		int (*lookup)(struct sock *sk, struct sk_buff *skb);
-		struct udp_sock *up = udp_sk(sk);
+		up = udp_sk(sk);
 
 		lookup = READ_ONCE(up->encap_err_lookup);
 		if (!lookup || lookup(sk, skb))
 			sk = NULL;
 	}
 
+out:
 	if (!sk)
 		sk = ERR_PTR(__udp4_lib_err_encap_no_sk(skb, info));
 
@@ -707,15 +719,16 @@ int __udp4_lib_err(struct sk_buff *skb, u32 info, struct udp_table *udptable)
 	sk = __udp4_lib_lookup(net, iph->daddr, uh->dest,
 			       iph->saddr, uh->source, skb->dev->ifindex,
 			       inet_sdif(skb), udptable, NULL);
+
 	if (!sk || udp_sk(sk)->encap_type) {
 		/* No socket for error: try tunnels before discarding */
-		sk = ERR_PTR(-ENOENT);
 		if (static_branch_unlikely(&udp_encap_needed_key)) {
-			sk = __udp4_lib_err_encap(net, iph, uh, udptable, skb,
+			sk = __udp4_lib_err_encap(net, iph, uh, udptable, sk, skb,
 						  info);
 			if (!sk)
 				return 0;
-		}
+		} else
+			sk = ERR_PTR(-ENOENT);
 
 		if (IS_ERR(sk)) {
 			__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);