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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>
This commit is contained in:
Pravin B Shelar 2013-09-24 10:25:40 -07:00 committed by David S. Miller
parent 9a3bab6b05
commit 559835ea72
2 changed files with 8 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
drivers/net/vxlan.c
View File

@ -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));

5
include/net/sock.h
View File

@ -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