rds: tcp: Reorder initialization sequence in rds_tcp_init to avoid races

Order of initialization in rds_tcp_init needs to be done so
that resources are set up and destroyed in the correct synchronization
sequence with both the data path, as well as netns create/destroy
path. Specifically,

- we must call register_pernet_subsys and get the rds_tcp_netid
  before calling register_netdevice_notifier, otherwise we risk
  the sequence
    1. register_netdevice_notifier sets up netdev notifier callback
    2. rds_tcp_dev_event -> rds_tcp_kill_sock uses netid 0, and finds
       the wrong rtn, resulting in a panic with string that is of the form:

  BUG: unable to handle kernel NULL pointer dereference at 000000000000000d
  IP: rds_tcp_kill_sock+0x3a/0x1d0 [rds_tcp]
         :

- the rds_tcp_incoming_slab kmem_cache must be initialized before the
  datapath starts up. The latter can happen any time after the
  pernet_subsys registration of rds_tcp_net_ops, whose -> init
  function sets up the listen socket. If the rds_tcp_incoming_slab has
  not been set up at that time, a panic of the form below may be
  encountered

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000014
  IP: kmem_cache_alloc+0x90/0x1c0
     :
  rds_tcp_data_recv+0x1e7/0x370 [rds_tcp]
  tcp_read_sock+0x96/0x1c0
  rds_tcp_recv_path+0x65/0x80 [rds_tcp]
     :

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 65c8e3b..fbf807a 100644 (file)
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -638,19 +638,19 @@ static int rds_tcp_init(void)
                goto out;
        }
 
-       ret = register_netdevice_notifier(&rds_tcp_dev_notifier);
-       if (ret) {
-               pr_warn("could not register rds_tcp_dev_notifier\n");
+       ret = rds_tcp_recv_init();
+       if (ret)
                goto out_slab;
-       }
 
        ret = register_pernet_subsys(&rds_tcp_net_ops);
        if (ret)
-               goto out_notifier;
+               goto out_recv;
 
-       ret = rds_tcp_recv_init();
-       if (ret)
+       ret = register_netdevice_notifier(&rds_tcp_dev_notifier);
+       if (ret) {
+               pr_warn("could not register rds_tcp_dev_notifier\n");
                goto out_pernet;
+       }
 
        rds_trans_register(&rds_tcp_transport);
 
@@ -660,9 +660,8 @@ static int rds_tcp_init(void)
 
 out_pernet:
        unregister_pernet_subsys(&rds_tcp_net_ops);
-out_notifier:
-       if (unregister_netdevice_notifier(&rds_tcp_dev_notifier))
-               pr_warn("could not unregister rds_tcp_dev_notifier\n");
+out_recv:
+       rds_tcp_recv_exit();
 out_slab:
        kmem_cache_destroy(rds_tcp_conn_slab);
 out: