tcp: annotate sk->sk_rcvbuf lockless reads

For the sake of tcp_poll(), there are few places where we fetch
sk->sk_rcvbuf while this field can change from IRQ or other cpu.

We need to add READ_ONCE() annotations, and also make sure write
sides use corresponding WRITE_ONCE() to avoid store-tearing.

Note that other transports probably need similar fixes.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index e1d08f69fd39..ab4eb5eb5d07 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1380,14 +1380,14 @@ static inline int tcp_win_from_space(const struct sock *sk, int space)
 /* Note: caller must be prepared to deal with negative returns */
 static inline int tcp_space(const struct sock *sk)
 {
-        return tcp_win_from_space(sk, sk->sk_rcvbuf -
+        return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) -
                                   READ_ONCE(sk->sk_backlog.len) -
                                   atomic_read(&sk->sk_rmem_alloc));
 }
 
 static inline int tcp_full_space(const struct sock *sk)
 {
-        return tcp_win_from_space(sk, sk->sk_rcvbuf);
+        return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));
 }
 
 extern void tcp_openreq_init_rwin(struct request_sock *req,