[PATCH net] sctp: check duplicate node before inserting a new transport

[Xin Long]

sctp has changed to use rhlist for transport rhashtable since commit
7fda702f9315 ("sctp: use new rhlist interface on sctp transport
rhashtable").

But rhltable_insert_key doesn't check the duplicate node when inserting
a node, unlike rhashtable_lookup_insert_key. It may cause duplicate
assoc/transport in rhashtable. like:

 client (addr A, B)                 server (addr X, Y)
    connect to X           INIT (1)
                        ------------>
    connect to Y           INIT (2)
                        ------------>
                         INIT_ACK (1)
                        <------------
                         INIT_ACK (2)
                        <------------

After sending INIT (2), one transport will be created and hashed into
rhashtable. But when receiving INIT_ACK (1) and processing the address
params, another transport will be created and hashed into rhashtable
with the same addr Y and EP as the last transport. This will confuse
the assoc/transport's lookup.

This patch is to fix it by returning err if any duplicate node exists
before inserting it.

Fixes: 7fda702f9315 ("sctp: use new rhlist interface on sctp transport 
rhashtable")
Reported-by: Fabio M. Di Nitto <fdini...@redhat.com>
Signed-off-by: Xin Long <lucien....@gmail.com>
---
 net/sctp/input.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 458e506..f65245b 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -872,6 +872,8 @@ void sctp_transport_hashtable_destroy(void)
 
 int sctp_hash_transport(struct sctp_transport *t)
 {
+       struct sctp_transport *transport;
+       struct rhlist_head *tmp, *list;
        struct sctp_hash_cmp_arg arg;
        int err;
 
@@ -882,8 +884,19 @@ int sctp_hash_transport(struct sctp_transport *t)
        arg.paddr = &t->ipaddr;
        arg.lport = htons(t->asoc->base.bind_addr.port);
 
+       list = rhltable_lookup(&sctp_transport_hashtable, &arg,
+                              sctp_hash_params);
+
+       rhl_for_each_entry_rcu(transport, tmp, list, node)
+               if (transport->asoc->ep == t->asoc->ep) {
+                       err = -EEXIST;
+                       goto out;
+               }
+
        err = rhltable_insert_key(&sctp_transport_hashtable, &arg,
                                  &t->node, sctp_hash_params);
+
+out:
        if (err)
                pr_err_once("insert transport fail, errno %d\n", err);
 
-- 
2.1.0