From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pravin B Shelar Subject: [PATCH net] vxlan: Use RCU apis to access sk_user_data. Date: Mon, 23 Sep 2013 22:28:21 -0700 Message-ID: <1380000501-13969-1-git-send-email-pshelar@nicira.com> Cc: Pravin B Shelar , Jesse Gross To: netdev@vger.kernel.org Return-path: Received: from na3sys009aog122.obsmtp.com ([74.125.149.147]:54413 "HELO na3sys009aog122.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750714Ab3IXF2h (ORCPT ); Tue, 24 Sep 2013 01:28:37 -0400 Received: by mail-ie0-f174.google.com with SMTP id u16so8100923iet.5 for ; Mon, 23 Sep 2013 22:28:24 -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 --- drivers/net/vxlan.c | 9 +++------ include/net/sock.h | 2 ++ 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c index d1292fe..3519a71 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_pointer(sk_user_data_rcu(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_rcu(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_pointer(sk_user_data_rcu(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..ffd1356 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -409,6 +409,8 @@ struct sock { void (*sk_destruct)(struct sock *sk); }; +#define sk_user_data_rcu(sk) ((*((void __rcu **)&(sk)->sk_user_data))) + /* * 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