net: add missing data-race annotations around sk->sk_peek_off

sk_getsockopt() runs locklessly, thus we need to annotate the read
of sk->sk_peek_off.

While we are at it, add corresponding annotations to sk_set_peek_off()
and unix_set_peek_off().

Fixes: b9bb53f ("sock: convert sk_peek_offset functions to WRITE_ONCE")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: edumazet

net/core/sock.c

@@ -1870,7 +1870,7 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
 		if (!sock->ops->set_peek_off)
 			return -EOPNOTSUPP;
 
-		v.val = sk->sk_peek_off;
+		v.val = READ_ONCE(sk->sk_peek_off);
 		break;
 	case SO_NOFCS:
 		v.val = sock_flag(sk, SOCK_NOFCS);
@@ -3179,7 +3179,7 @@ EXPORT_SYMBOL(__sk_mem_reclaim);
 
 int sk_set_peek_off(struct sock *sk, int val)
 {
-	sk->sk_peek_off = val;
+	WRITE_ONCE(sk->sk_peek_off, val);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(sk_set_peek_off);

net/unix/af_unix.c

@@ -790,7 +790,7 @@ static int unix_set_peek_off(struct sock *sk, int val)
 	if (mutex_lock_interruptible(&u->iolock))
 		return -EINTR;
 
-	sk->sk_peek_off = val;
+	WRITE_ONCE(sk->sk_peek_off, val);
 	mutex_unlock(&u->iolock);
 
 	return 0;