Re: [PATCH net v3 1/2] 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 <redacted>
---
 net/ipv4/udp.c | 25 +++++++++++++++++++------
 net/ipv6/udp.c | 25 +++++++++++++++++++------
 2 files changed, 38 insertions(+), 12 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);

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 0cc7ba531b34..c5e15e94bb00 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c

@@ -502,12 +502,14 @@ static struct sock *__udp6_lib_err_encap(struct net *net,
                                         const struct ipv6hdr *hdr, int offset,
                                         struct udphdr *uh,
                                         struct udp_table *udptable,
+                                        struct sock *sk,
                                         struct sk_buff *skb,
                                         struct inet6_skb_parm *opt,
                                         u8 type, u8 code, __be32 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);

@@ -518,18 +520,28 @@ static struct sock *__udp6_lib_err_encap(struct net *net,
        /* Transport header needs to point to the UDP header */
        skb_set_transport_header(skb, offset);

+       if (sk) {
+               up = udp_sk(sk);
+
+               lookup = READ_ONCE(up->encap_err_lookup);
+               if (lookup && lookup(sk, skb))
+                       sk = NULL;
+
+               goto out;
+       }
+
        sk = __udp6_lib_lookup(net, &hdr->daddr, uh->source,
                               &hdr->saddr, uh->dest,
                               inet6_iif(skb), 0, udptable, skb);
        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(__udp6_lib_err_encap_no_sk(skb, opt, type, code,
                                                        offset, info));

@@ -558,16 +570,17 @@ int __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,

        sk = __udp6_lib_lookup(net, daddr, uh->dest, saddr, uh->source,
                               inet6_iif(skb), inet6_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(&udpv6_encap_needed_key)) {
                        sk = __udp6_lib_err_encap(net, hdr, offset, uh,
-                                                 udptable, skb,
+                                                 udptable, sk, skb,
                                                  opt, type, code, info);
                        if (!sk)
                                return 0;
-               }
+               } else
+                       sk = ERR_PTR(-ENOENT);

                if (IS_ERR(sk)) {
                        __ICMP6_INC_STATS(net, __in6_dev_get(skb->dev),
--

2.18.4