net/x25: fix nonblocking connect

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>

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 2efe44a346443d6715b271437d3c0d8de52f1f3e..d5b09bbff3754ff4138b6c6effe1c1e52901b266 100644 (file)
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -766,6 +766,10 @@ 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;
 
@@ -812,7 +816,7 @@ 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)