vxlan: Use RCU apis to access sk_user_data.

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 <jesse@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 6 deletions

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index d1292fe746bc..2ef5b6219f3f 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));