This is a note to let you know that I've just added the patch titled net/x25: Fix to not accept on connected socket to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-x25-fix-to-not-accept-on-connected-socket.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 33e4d9121c9efec5190028907350c8d0ddb4994c Author: Hyunwoo Kim <v4bel@xxxxxxxxx> Date: Mon Jan 23 11:43:23 2023 -0800 net/x25: Fix to not accept on connected socket [ Upstream commit f2b0b5210f67c56a3bcdf92ff665fb285d6e0067 ] 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@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c index 77d8adb27ec7..9d0328bb30ca 100644 --- a/net/x25/af_x25.c +++ b/net/x25/af_x25.c @@ -497,6 +497,12 @@ 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;