[PATCH AUTOSEL 5.15 10/12] net/x25: Fix to not accept on connected socket

Sasha Levin
2023-01-31T15:03:29Z

From: Hyunwoo Kim <v4bel@theori.io>

[ 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@theori.io>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/x25/af_x25.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 3a171828638b..07f6206e7cb4 100644
--- 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;
--
2.39.0