linux-kernel - Leaking path or inconsistency LSM checking observed in fs/net

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Date:   Tue, 25 Sep 2018 13:27:00 -0400
From:   Tong Zhang <ztong@...edu>
To:     mark@...heh.com, jlbec@...lplan.org, keescook@...omium.org,
        davem@...emloft.net, viro@...iv.linux.org.uk, dvlasenk@...hat.com,
        ccaulfie@...hat.com, teigland@...hat.com
Cc:     linux-kernel@...r.kernel.org, ocfs2-devel@....oracle.com,
        cluster-devel@...hat.com, linux-security-module@...r.kernel.org,
        Wenbo Shen <shenwenbosmile@...il.com>
Subject: Leaking path or inconsistency LSM checking observed in fs/net

Kernel Version: 4.18.5

Problem Description:

We found several leaking path or inconsistency LSM design issue in fs/net.

Currently we can only observe sock creation from kernel and all bind/listen/connect are not sent to LSM.
So, we think that those net/socket related stuff should all go through LSM check and being audited 
even it is not a user thread or process.


Here’s an example where we have a check: 
in fs/ocfs2/cluster/tcp.c:2035 o2net_open_listening_sock() a sock is created using sock_create(),
where a LSM check security_socket_create is called(net/socket.c:1242)


And where we don’t have a check

fs/ocfs2/cluster/tcp.c:2052 bind
fs/ocfs2/cluster/tcp.c:2059 listen

fs/dlm/lowcomms.c:1264 bind
fs/dlm/lowcomms.c:1278 listen
fs/dlm/lowcomms.c:1354 listen

several places that use kernel_bind/kernel_listen/kernel_connect

net/socket.c:3231 kernel_bind
net/socket.c:3237 kernel_listen
net/socket.c:3286 kernel_connect


- Tong