net/x25: Fix to not accept on connected socket

When listen() and accept() are called on an x25 socket
that connect() succeeds, accept() succeeds immediately.
This is because x25_connect() queues the skb to
sk->sk_receive_queue, and x25_accept() dequeues it.

This creates a child socket with the sk of the parent
x25 socket, which can cause confusion.

Fix x25_listen() to return -EINVAL if the socket has
already been successfully connect()ed to avoid this issue.

Signed-off-by: Hyunwoo Kim <v4bel@theori.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 3b55502..5c7ad30 100644 (file)
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -482,6 +482,12 @@ static int x25_listen(struct socket *sock, int backlog)
        int rc = -EOPNOTSUPP;
 
        lock_sock(sk);
+       if (sock->state != SS_UNCONNECTED) {
+               rc = -EINVAL;
+               release_sock(sk);
+               return rc;
+       }
+
        if (sk->sk_state != TCP_LISTEN) {
                memset(&x25_sk(sk)->dest_addr, 0, X25_ADDR_LEN);
                sk->sk_max_ack_backlog = backlog;