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Date:   Wed, 21 Jul 2021 10:08:22 -0400
From:   Xin Long <lucien.xin@...il.com>
To:     Vadim Fedorenko <vfedorenko@...ek.ru>
Cc:     David Ahern <dsahern@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        network dev <netdev@...r.kernel.org>
Subject: Re: [PATCH net v3 1/2] udp: check encap socket in __udp_lib_err

On Tue, Jul 20, 2021 at 4:35 PM Vadim Fedorenko <vfedorenko@...ek.ru> wrote:
>
> 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@...ek.ru>
> ---
>  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
>
Reviewed-by: Xin Long <lucien.xin@...il.com>

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