From 16c09b1c7657522a321b04aa7f4300865b7cb292 Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Sat, 4 Mar 2017 08:57:34 -0800 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- net/rds/tcp.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/net/rds/tcp.c b/net/rds/tcp.c index 65c8e3b..fbf807a 100644 --- 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: -- 2.7.4