release/5.2.38/net-x25-fix-nonblocking-connect.patch

From 1d22cf1586cb036c6e72dd9bab9f729778f64c5d Mon Sep 17 00:00:00 2001
From: Martin Schiller <ms@dev.tdt.de>
Date: Thu, 9 Jan 2020 07:31:14 +0100
Subject: [PATCH] net/x25: fix nonblocking connect

commit e21dba7a4df4d93da237da65a096084b4f2e87b4 upstream.

This patch fixes 2 issues in x25_connect():

1. It makes absolutely no sense to reset the neighbour and the
connection state after a (successful) nonblocking call of x25_connect.
This prevents any connection from being established, since the response
(call accept) cannot be processed.

2. Any further calls to x25_connect() while a call is pending should
simply return, instead of creating new Call Request (on different
logical channels).

This patch should also fix the "KASAN: null-ptr-deref Write in
x25_connect" and "BUG: unable to handle kernel NULL pointer dereference
in x25_connect" bugs reported by syzbot.

Signed-off-by: Martin Schiller <ms@dev.tdt.de>
Reported-by: syzbot+429c200ffc8772bfe070@syzkaller.appspotmail.com
Reported-by: syzbot+eec0c87f31a7c3b66f7b@syzkaller.appspotmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 6aee9f5e8e71..256f3e97d1f3 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -760,6 +760,10 @@ static int x25_connect(struct socket *sock, struct sockaddr *uaddr,
 	if (sk->sk_state == TCP_ESTABLISHED)
 		goto out;
 
+	rc = -EALREADY;	/* Do nothing if call is already in progress */
+	if (sk->sk_state == TCP_SYN_SENT)
+		goto out;
+
 	sk->sk_state   = TCP_CLOSE;
 	sock->state = SS_UNCONNECTED;
 
@@ -806,7 +810,7 @@ static int x25_connect(struct socket *sock, struct sockaddr *uaddr,
 	/* Now the loop */
 	rc = -EINPROGRESS;
 	if (sk->sk_state != TCP_ESTABLISHED && (flags & O_NONBLOCK))
-		goto out_put_neigh;
+		goto out;
 
 	rc = x25_wait_for_connection_establishment(sk);
 	if (rc)
-- 
2.7.4