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, 5 insertions, 0 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 6ba2e7b0e2b1..1d37a8086bed 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -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