Re: [PATCH net-next v2 1/2] net: Update bhash2 when socket's rcv saddr changes

[Paolo Abeni <pabeni@redhat.com>]

On Tue, 2022-06-07 at 13:24 -0700, Joanne Koong wrote:
> On Tue, Jun 7, 2022 at 1:33 AM Paolo Abeni <pabeni@redhat.com> wrote:
> > 
> > Hello,
> > 
> > On Thu, 2022-06-02 at 09:51 -0700, Joanne Koong wrote:
> > > Commit d5a42de8bdbe ("net: Add a second bind table hashed by port and
> > > address") added a second bind table, bhash2, that hashes by a socket's port
> > > and rcv address.
> > > 
> > > However, there are two cases where the socket's rcv saddr can change
> > > after it has been binded:
> > > 
> > > 1) The case where there is a bind() call on "::" (IPADDR_ANY) and then
> > > a connect() call. The kernel will assign the socket an address when it
> > > handles the connect()
> > > 
> > > 2) In inet_sk_reselect_saddr(), which is called when rerouting fails
> > > when rebuilding the sk header (invoked by inet_sk_rebuild_header)
> > > 
> > > In these two cases, we need to update the bhash2 table by removing the
> > > entry for the old address, and adding a new entry reflecting the updated
> > > address.
> > > 
> > > Reported-by: syzbot+015d756bbd1f8b5c8f09@syzkaller.appspotmail.com
> > > Fixes: d5a42de8bdbe ("net: Add a second bind table hashed by port and address")
> > > Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
> > > Reviewed-by: Eric Dumazet <edumazet@google.com>
> > > ---
> > >  include/net/inet_hashtables.h |  6 ++-
> > >  include/net/ipv6.h            |  2 +-
> > >  net/dccp/ipv4.c               | 10 +++--
> > >  net/dccp/ipv6.c               |  4 +-
> > >  net/ipv4/af_inet.c            |  7 +++-
> > >  net/ipv4/inet_hashtables.c    | 70 ++++++++++++++++++++++++++++++++---
> > >  net/ipv4/tcp_ipv4.c           |  8 +++-
> > >  net/ipv6/inet6_hashtables.c   |  4 +-
> > >  net/ipv6/tcp_ipv6.c           |  4 +-
> > >  9 files changed, 97 insertions(+), 18 deletions(-)
> > > 
> > > diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
> > > index a0887b70967b..2c331ce6ca73 100644
> > > --- a/include/net/inet_hashtables.h
> > > +++ b/include/net/inet_hashtables.h
> > > @@ -448,11 +448,13 @@ static inline void sk_rcv_saddr_set(struct sock *sk, __be32 addr)
> > >  }
> > > 
> > >  int __inet_hash_connect(struct inet_timewait_death_row *death_row,
> > > -                     struct sock *sk, u64 port_offset,
> > > +                     struct sock *sk, u64 port_offset, bool prev_inaddr_any,
> > >                       int (*check_established)(struct inet_timewait_death_row *,
> > >                                                struct sock *, __u16,
> > >                                                struct inet_timewait_sock **));
> > > 
> > >  int inet_hash_connect(struct inet_timewait_death_row *death_row,
> > > -                   struct sock *sk);
> > > +                   struct sock *sk, bool prev_inaddr_any);
> > > +
> > > +int inet_bhash2_update_saddr(struct sock *sk);
> > >  #endif /* _INET_HASHTABLES_H */
> > > diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> > > index 5b38bf1a586b..6a50aca56d50 100644
> > > --- a/include/net/ipv6.h
> > > +++ b/include/net/ipv6.h
> > > @@ -1187,7 +1187,7 @@ int inet6_compat_ioctl(struct socket *sock, unsigned int cmd,
> > >               unsigned long arg);
> > > 
> > >  int inet6_hash_connect(struct inet_timewait_death_row *death_row,
> > > -                           struct sock *sk);
> > > +                    struct sock *sk, bool prev_inaddr_any);
> > >  int inet6_sendmsg(struct socket *sock, struct msghdr *msg, size_t size);
> > >  int inet6_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> > >                 int flags);
> > > diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
> > > index da6e3b20cd75..37a8bc3ee49e 100644
> > > --- a/net/dccp/ipv4.c
> > > +++ b/net/dccp/ipv4.c
> > > @@ -47,12 +47,13 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> > >       const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
> > >       struct inet_sock *inet = inet_sk(sk);
> > >       struct dccp_sock *dp = dccp_sk(sk);
> > > +     struct ip_options_rcu *inet_opt;
> > >       __be16 orig_sport, orig_dport;
> > > +     bool prev_inaddr_any = false;
> > >       __be32 daddr, nexthop;
> > >       struct flowi4 *fl4;
> > >       struct rtable *rt;
> > >       int err;
> > > -     struct ip_options_rcu *inet_opt;
> > > 
> > >       dp->dccps_role = DCCP_ROLE_CLIENT;
> > > 
> > > @@ -89,8 +90,11 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> > >       if (inet_opt == NULL || !inet_opt->opt.srr)
> > >               daddr = fl4->daddr;
> > > 
> > > -     if (inet->inet_saddr == 0)
> > > +     if (inet->inet_saddr == 0) {
> > >               inet->inet_saddr = fl4->saddr;
> > > +             prev_inaddr_any = true;
> > > +     }
> > > +
> > >       sk_rcv_saddr_set(sk, inet->inet_saddr);
> > >       inet->inet_dport = usin->sin_port;
> > >       sk_daddr_set(sk, daddr);
> > > @@ -105,7 +109,7 @@ int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> > >        * complete initialization after this.
> > >        */
> > >       dccp_set_state(sk, DCCP_REQUESTING);
> > > -     err = inet_hash_connect(&dccp_death_row, sk);
> > > +     err = inet_hash_connect(&dccp_death_row, sk, prev_inaddr_any);
> > >       if (err != 0)
> > >               goto failure;
> > > 
> > > diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
> > > index fd44638ec16b..03013522acab 100644
> > > --- a/net/dccp/ipv6.c
> > > +++ b/net/dccp/ipv6.c
> > > @@ -824,6 +824,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
> > >       struct ipv6_pinfo *np = inet6_sk(sk);
> > >       struct dccp_sock *dp = dccp_sk(sk);
> > >       struct in6_addr *saddr = NULL, *final_p, final;
> > > +     bool prev_inaddr_any = false;
> > >       struct ipv6_txoptions *opt;
> > >       struct flowi6 fl6;
> > >       struct dst_entry *dst;
> > > @@ -936,6 +937,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
> > >       if (saddr == NULL) {
> > >               saddr = &fl6.saddr;
> > >               sk->sk_v6_rcv_saddr = *saddr;
> > > +             prev_inaddr_any = true;
> > >       }
> > > 
> > >       /* set the source address */
> > > @@ -951,7 +953,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
> > >       inet->inet_dport = usin->sin6_port;
> > > 
> > >       dccp_set_state(sk, DCCP_REQUESTING);
> > > -     err = inet6_hash_connect(&dccp_death_row, sk);
> > > +     err = inet6_hash_connect(&dccp_death_row, sk, prev_inaddr_any);
> > >       if (err)
> > >               goto late_failure;
> > > 
> > > diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> > > index 93da9f783bec..ad627a99ff9d 100644
> > > --- a/net/ipv4/af_inet.c
> > > +++ b/net/ipv4/af_inet.c
> > > @@ -1221,10 +1221,11 @@ static int inet_sk_reselect_saddr(struct sock *sk)
> > >       struct inet_sock *inet = inet_sk(sk);
> > >       __be32 old_saddr = inet->inet_saddr;
> > >       __be32 daddr = inet->inet_daddr;
> > > +     struct ip_options_rcu *inet_opt;
> > >       struct flowi4 *fl4;
> > >       struct rtable *rt;
> > >       __be32 new_saddr;
> > > -     struct ip_options_rcu *inet_opt;
> > > +     int err;
> > > 
> > >       inet_opt = rcu_dereference_protected(inet->inet_opt,
> > >                                            lockdep_sock_is_held(sk));
> > > @@ -1253,6 +1254,10 @@ static int inet_sk_reselect_saddr(struct sock *sk)
> > > 
> > >       inet->inet_saddr = inet->inet_rcv_saddr = new_saddr;
> > > 
> > > +     err = inet_bhash2_update_saddr(sk);
> > > +     if (err)
> > > +             return err;
> > > +
> > >       /*
> > >        * XXX The only one ugly spot where we need to
> > >        * XXX really change the sockets identity after
> > > diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
> > > index e8de5e699b3f..592b70663a3b 100644
> > > --- a/net/ipv4/inet_hashtables.c
> > > +++ b/net/ipv4/inet_hashtables.c
> > > @@ -826,6 +826,55 @@ inet_bind2_bucket_find(struct inet_hashinfo *hinfo, struct net *net,
> > >       return bhash2;
> > >  }
> > > 
> > > +/* the lock for the socket's corresponding bhash entry must be held */
> > > +static int __inet_bhash2_update_saddr(struct sock *sk,
> > > +                                   struct inet_hashinfo *hinfo,
> > > +                                   struct net *net, int port, int l3mdev)
> > > +{
> > > +     struct inet_bind2_hashbucket *head2;
> > > +     struct inet_bind2_bucket *tb2;
> > > +
> > > +     tb2 = inet_bind2_bucket_find(hinfo, net, port, l3mdev, sk,
> > > +                                  &head2);
> > > +     if (!tb2) {
> > > +             tb2 = inet_bind2_bucket_create(hinfo->bind2_bucket_cachep,
> > > +                                            net, head2, port, l3mdev, sk);
> > > +             if (!tb2)
> > > +                     return -ENOMEM;
> > > +     }
> > > +
> > > +     /* Remove the socket's old entry from bhash2 */
> > > +     __sk_del_bind2_node(sk);
> > > +
> > > +     sk_add_bind2_node(sk, &tb2->owners);
> > > +     inet_csk(sk)->icsk_bind2_hash = tb2;
> > > +
> > > +     return 0;
> > > +}
> > > +
> > > +/* This should be called if/when a socket's rcv saddr changes after it has
> > > + * been binded.
> > > + */
> > > +int inet_bhash2_update_saddr(struct sock *sk)
> > > +{
> > > +     struct inet_hashinfo *hinfo = sk->sk_prot->h.hashinfo;
> > > +     int l3mdev = inet_sk_bound_l3mdev(sk);
> > > +     struct inet_bind_hashbucket *head;
> > > +     int port = inet_sk(sk)->inet_num;
> > > +     struct net *net = sock_net(sk);
> > > +     int err;
> > > +
> > > +     head = &hinfo->bhash[inet_bhashfn(net, port, hinfo->bhash_size)];
> > > +
> > > +     spin_lock_bh(&head->lock);
> > > +
> > > +     err = __inet_bhash2_update_saddr(sk, hinfo, net, port, l3mdev);
> > > +
> > > +     spin_unlock_bh(&head->lock);
> > > +
> > > +     return err;
> > > +}
> > > +
> > >  /* RFC 6056 3.3.4.  Algorithm 4: Double-Hash Port Selection Algorithm
> > >   * Note that we use 32bit integers (vs RFC 'short integers')
> > >   * because 2^16 is not a multiple of num_ephemeral and this
> > > @@ -840,7 +889,7 @@ inet_bind2_bucket_find(struct inet_hashinfo *hinfo, struct net *net,
> > >  static u32 *table_perturb;
> > > 
> > >  int __inet_hash_connect(struct inet_timewait_death_row *death_row,
> > > -             struct sock *sk, u64 port_offset,
> > > +             struct sock *sk, u64 port_offset, bool prev_inaddr_any,
> > >               int (*check_established)(struct inet_timewait_death_row *,
> > >                       struct sock *, __u16, struct inet_timewait_sock **))
> > >  {
> > > @@ -858,11 +907,24 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
> > >       int l3mdev;
> > >       u32 index;
> > > 
> > > +     l3mdev = inet_sk_bound_l3mdev(sk);
> > > +
> > >       if (port) {
> > >               head = &hinfo->bhash[inet_bhashfn(net, port,
> > >                                                 hinfo->bhash_size)];
> > >               tb = inet_csk(sk)->icsk_bind_hash;
> > > +
> > >               spin_lock_bh(&head->lock);
> > > +
> > > +             if (prev_inaddr_any) {
> > > +                     ret = __inet_bhash2_update_saddr(sk, hinfo, net, port,
> > > +                                                      l3mdev);
> > > +                     if (ret) {
> > > +                             spin_unlock_bh(&head->lock);
> > > +                             return ret;
> > > +                     }
> > > +             }
> > > +
> > >               if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
> > >                       inet_ehash_nolisten(sk, NULL, NULL);
> > >                       spin_unlock_bh(&head->lock);
> > > @@ -875,8 +937,6 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
> > >               return ret;
> > >       }
> > > 
> > > -     l3mdev = inet_sk_bound_l3mdev(sk);
> > > -
> > >       inet_get_local_port_range(net, &low, &high);
> > >       high++; /* [32768, 60999] -> [32768, 61000[ */
> > >       remaining = high - low;
> > > @@ -987,13 +1047,13 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row,
> > >   * Bind a port for a connect operation and hash it.
> > >   */
> > >  int inet_hash_connect(struct inet_timewait_death_row *death_row,
> > > -                   struct sock *sk)
> > > +                   struct sock *sk, bool prev_inaddr_any)
> > >  {
> > >       u64 port_offset = 0;
> > > 
> > >       if (!inet_sk(sk)->inet_num)
> > >               port_offset = inet_sk_port_offset(sk);
> > > -     return __inet_hash_connect(death_row, sk, port_offset,
> > > +     return __inet_hash_connect(death_row, sk, port_offset, prev_inaddr_any,
> > >                                  __inet_check_established);
> > >  }
> > >  EXPORT_SYMBOL_GPL(inet_hash_connect);
> > > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> > > index dac2650f3863..adf8d750933d 100644
> > > --- a/net/ipv4/tcp_ipv4.c
> > > +++ b/net/ipv4/tcp_ipv4.c
> > > @@ -203,6 +203,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> > >       struct inet_sock *inet = inet_sk(sk);
> > >       struct tcp_sock *tp = tcp_sk(sk);
> > >       __be16 orig_sport, orig_dport;
> > > +     bool prev_inaddr_any = false;
> > >       __be32 daddr, nexthop;
> > >       struct flowi4 *fl4;
> > >       struct rtable *rt;
> > > @@ -246,8 +247,11 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> > >       if (!inet_opt || !inet_opt->opt.srr)
> > >               daddr = fl4->daddr;
> > > 
> > > -     if (!inet->inet_saddr)
> > > +     if (!inet->inet_saddr) {
> > >               inet->inet_saddr = fl4->saddr;
> > > +             prev_inaddr_any = true;
> > > +     }
> > > +
> > >       sk_rcv_saddr_set(sk, inet->inet_saddr);
> > > 
> > >       if (tp->rx_opt.ts_recent_stamp && inet->inet_daddr != daddr) {
> > > @@ -273,7 +277,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
> > >        * complete initialization after this.
> > >        */
> > >       tcp_set_state(sk, TCP_SYN_SENT);
> > > -     err = inet_hash_connect(tcp_death_row, sk);
> > > +     err = inet_hash_connect(tcp_death_row, sk, prev_inaddr_any);
> > >       if (err)
> > >               goto failure;
> > > 
> > > diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
> > > index 7d53d62783b1..c87c5933f3be 100644
> > > --- a/net/ipv6/inet6_hashtables.c
> > > +++ b/net/ipv6/inet6_hashtables.c
> > > @@ -317,13 +317,13 @@ static u64 inet6_sk_port_offset(const struct sock *sk)
> > >  }
> > > 
> > >  int inet6_hash_connect(struct inet_timewait_death_row *death_row,
> > > -                    struct sock *sk)
> > > +                    struct sock *sk, bool prev_inaddr_any)
> > >  {
> > >       u64 port_offset = 0;
> > > 
> > >       if (!inet_sk(sk)->inet_num)
> > >               port_offset = inet6_sk_port_offset(sk);
> > > -     return __inet_hash_connect(death_row, sk, port_offset,
> > > +     return __inet_hash_connect(death_row, sk, port_offset, prev_inaddr_any,
> > >                                  __inet6_check_established);
> > >  }
> > >  EXPORT_SYMBOL_GPL(inet6_hash_connect);
> > > diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> > > index f37dd4aa91c6..81e3312c2a97 100644
> > > --- a/net/ipv6/tcp_ipv6.c
> > > +++ b/net/ipv6/tcp_ipv6.c
> > > @@ -152,6 +152,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
> > >       struct ipv6_pinfo *np = tcp_inet6_sk(sk);
> > >       struct tcp_sock *tp = tcp_sk(sk);
> > >       struct in6_addr *saddr = NULL, *final_p, final;
> > > +     bool prev_inaddr_any = false;
> > >       struct ipv6_txoptions *opt;
> > >       struct flowi6 fl6;
> > >       struct dst_entry *dst;
> > > @@ -289,6 +290,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
> > >       if (!saddr) {
> > >               saddr = &fl6.saddr;
> > >               sk->sk_v6_rcv_saddr = *saddr;
> > > +             prev_inaddr_any = true;
> > >       }
> > > 
> > >       /* set the source address */
> > > @@ -309,7 +311,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
> > > 
> > >       tcp_set_state(sk, TCP_SYN_SENT);
> > >       tcp_death_row = sock_net(sk)->ipv4.tcp_death_row;
> > > -     err = inet6_hash_connect(tcp_death_row, sk);
> > > +     err = inet6_hash_connect(tcp_death_row, sk, prev_inaddr_any);
> > >       if (err)
> > >               goto late_failure;
> > > 
> > 
> > I'm sorry for the late notice, but it looks like that the mptcp
> > syzkaller instance is still hitting the Warning in icsk_get_port on top
> > of the v1 of this series:
> > 
> > https://github.com/multipath-tcp/mptcp_net-next/issues/279
> > 
> > and the change in v2 should not address that. @Mat could you please
> > confirm the above?
> > 
> > Dumb question: I don't understand how the locking in bhash2 works.
> > Could you explain that?
> > 
> > What happens when 2 different processes bind different sockets on
> > different ports (with different bhash buckets) using different
> > addresses so that they hit the same bhash2 bucket? AFAICS each process
> > will use a different lock and access/modification to bhash2 could
> > happen simultaneusly?
> Hi Paolo. Yes, I think you are correct here that there could be a
> scenario where this happens. Unfortunately, I think this means the
> bhash2 table will need its own lock. I will submit a follow-up for
> this.
> 

I'm wondering if we could (and more importantly, if it would make any
sense) resort to use bhash2 usage only?

e.g. add a spinlock per row to bhash2, use it to protect row
manipulation, always hash into bhash2 and then drop bhash, similar to
commit cae3873c5b3a4fcd9706fb461ff4e91bdf1f0120?

Cheers,

Paolo