From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pravin B Shelar Subject: [PATCH net v3] vxlan: Use RCU apis to access sk_user_data. Date: Tue, 24 Sep 2013 10:25:40 -0700 Message-ID: <1380043540-10417-1-git-send-email-pshelar@nicira.com> Cc: eric.dumazet@gmail.com, stephen@networkplumber.org, Pravin B Shelar , Jesse Gross To: netdev@vger.kernel.org Return-path: Received: from na3sys009aog116.obsmtp.com ([74.125.149.240]:50292 "HELO na3sys009aog116.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753208Ab3IXRZv (ORCPT ); Tue, 24 Sep 2013 13:25:51 -0400 Received: by mail-ob0-f175.google.com with SMTP id uz6so5224775obc.6 for ; Tue, 24 Sep 2013 10:25:50 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: Use of RCU api makes vxlan code easier to understand. It also fixes bug due to missing ACCESS_ONCE() on sk_user_data dereference. In rare case without ACCESS_ONCE() compiler might omit vs on sk_user_data dereference. Compiler can use vs as alias for sk->sk_user_data, resulting in multiple sk_user_data dereference in rcu read context which could change. CC: Jesse Gross Signed-off-by: Pravin B Shelar --- v3: remove extra space User rcu_deref and rcu_assign api for accessing sk_user_data v2: Use RCU_INIT_POINTER --- drivers/net/vxlan.c | 9 +++------ include/net/sock.h | 5 +++++ 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c index d1292fe..2ef5b62 100644 --- a/drivers/net/vxlan.c +++ b/drivers/net/vxlan.c @@ -952,8 +952,7 @@ void vxlan_sock_release(struct vxlan_sock *vs) spin_lock(&vn->sock_lock); hlist_del_rcu(&vs->hlist); - smp_wmb(); - vs->sock->sk->sk_user_data = NULL; + rcu_assign_sk_user_data(vs->sock->sk, NULL); vxlan_notify_del_rx_port(sk); spin_unlock(&vn->sock_lock); @@ -1048,8 +1047,7 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb) port = inet_sk(sk)->inet_sport; - smp_read_barrier_depends(); - vs = (struct vxlan_sock *)sk->sk_user_data; + vs = rcu_dereference_sk_user_data(sk); if (!vs) goto drop; @@ -2302,8 +2300,7 @@ static struct vxlan_sock *vxlan_socket_create(struct net *net, __be16 port, atomic_set(&vs->refcnt, 1); vs->rcv = rcv; vs->data = data; - smp_wmb(); - vs->sock->sk->sk_user_data = vs; + rcu_assign_sk_user_data(vs->sock->sk, vs); spin_lock(&vn->sock_lock); hlist_add_head_rcu(&vs->hlist, vs_head(net, port)); diff --git a/include/net/sock.h b/include/net/sock.h index 6ba2e7b..1d37a80 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -409,6 +409,11 @@ struct sock { void (*sk_destruct)(struct sock *sk); }; +#define __sk_user_data(sk) ((*((void __rcu **)&(sk)->sk_user_data))) + +#define rcu_dereference_sk_user_data(sk) rcu_dereference(__sk_user_data((sk))) +#define rcu_assign_sk_user_data(sk, ptr) rcu_assign_pointer(__sk_user_data((sk)), ptr) + /* * SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK * or not whether his port will be reused by someone else. SK_FORCE_REUSE -- 1.7.1