Commit 559835ea authored by Pravin B Shelar's avatar Pravin B Shelar Committed by David S. Miller
Browse files

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: default avatarPravin B Shelar <pshelar@nicira.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9a3bab6b

drivers/net/vxlan.c

+3 −6
Original line number Diff line number Diff line
@@ -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));

include/net/sock.h

+5 −0
Original line number Diff line number Diff line
@@ -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

CRA Git | Maintained and supported by SUSTech CRA and CCSE