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vxlan: Use RCU apis to access sk_user_data.

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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 <[email protected]>
Signed-off-by: Pravin B Shelar <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Pravin B Shelar 2013-09-24 10:25:40 -07:00 • committed by David S. Miller
commit 559835ea72
2 changed files with 8 additions and 6 deletions
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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));