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>
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@ -952,8 +952,7 @@ void vxlan_sock_release(struct vxlan_sock *vs)
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spin_lock(&vn->sock_lock);
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hlist_del_rcu(&vs->hlist);
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smp_wmb();
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vs->sock->sk->sk_user_data = NULL;
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rcu_assign_sk_user_data(vs->sock->sk, NULL);
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vxlan_notify_del_rx_port(sk);
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spin_unlock(&vn->sock_lock);
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@ -1048,8 +1047,7 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
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port = inet_sk(sk)->inet_sport;
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smp_read_barrier_depends();
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vs = (struct vxlan_sock *)sk->sk_user_data;
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vs = rcu_dereference_sk_user_data(sk);
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if (!vs)
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goto drop;
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@ -2302,8 +2300,7 @@ static struct vxlan_sock *vxlan_socket_create(struct net *net, __be16 port,
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atomic_set(&vs->refcnt, 1);
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vs->rcv = rcv;
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vs->data = data;
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smp_wmb();
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vs->sock->sk->sk_user_data = vs;
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rcu_assign_sk_user_data(vs->sock->sk, vs);
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spin_lock(&vn->sock_lock);
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hlist_add_head_rcu(&vs->hlist, vs_head(net, port));
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@ -409,6 +409,11 @@ struct sock {
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void (*sk_destruct)(struct sock *sk);
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};
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#define __sk_user_data(sk) ((*((void __rcu **)&(sk)->sk_user_data)))
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#define rcu_dereference_sk_user_data(sk) rcu_dereference(__sk_user_data((sk)))
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#define rcu_assign_sk_user_data(sk, ptr) rcu_assign_pointer(__sk_user_data((sk)), ptr)
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/*
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* SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK
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* or not whether his port will be reused by someone else. SK_FORCE_REUSE
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