ksmbd: block asynchronous requests when making a delay on session setup

commit b096d97 upstream.

ksmbd make a delay of 5 seconds on session setup to avoid dictionary
attacks. But the 5 seconds delay can be bypassed by using asynchronous
requests. This patch block all requests on current connection when
making a delay on sesstion setup failure.

Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-20482
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/ksmbd/smb2pdu.c

@@ -1874,8 +1874,11 @@ int smb2_sess_setup(struct ksmbd_work *work)
 				try_delay = true;
 
 			sess->state = SMB2_SESSION_EXPIRED;
-			if (try_delay)
+			if (try_delay) {
+				ksmbd_conn_set_need_reconnect(conn);
 				ssleep(5);
+				ksmbd_conn_set_need_negotiate(conn);
+			}
 		}
 	}