netdev - [PATCH AUTOSEL 4.19 4/4] net/x25: Fix to not accept on connected socket

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Message-Id: <20230131150118.1250409-4-sashal@kernel.org>
Date:   Tue, 31 Jan 2023 10:01:18 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Hyunwoo Kim <v4bel@...ori.io>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, ms@....tdt.de,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        linux-x25@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 4/4] net/x25: Fix to not accept on connected socket

From: Hyunwoo Kim <v4bel@...ori.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@...ori.io>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.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 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;
-- 
2.39.0