linux-kernel - Re: Leaking path for set_task

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <0CD63E6E-7512-4DD6-8858-4408416DC730@vt.edu>
Date:   Tue, 25 Sep 2018 20:44:39 -0400
From:   TongZhang <ztong@...edu>
To:     Cyrill Gorcunov <gorcunov@...il.com>
Cc:     adobriyan@...il.com, akpm@...ux-foundation.org,
        viro@...iv.linux.org.uk, LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Wenbo Shen <shenwenbosmile@...il.com>
Subject: Re: Leaking path for set_task_comm

Yes, this is exactly what I am saying.
A process can change its own name using prctl or /proc/self/comm.
prctl is protected by security_task_prctl, whereas /proc/self/comm is not protected by this LSM hook.

A system admin may expect to use security_task_prctl to block all attempt to change process name, however, it can still change name using /proc/self/comm.

> On Sep 25, 2018, at 2:39 PM, Cyrill Gorcunov <gorcunov@...il.com> wrote:
> 
> On Tue, Sep 25, 2018 at 01:27:08PM -0400, Tong Zhang wrote:
>> Kernel Version: 4.18.5
>> 
>> Problem Description:
>> 
>> When using prctl(PR_SET_NAME) to set the thread name, it is checked by security_task_prctl.
>> 
>> We discovered a leaking path that can also use method implemented in 
>> fs/proc/base.c:1526 comm_write(), to do similar thing without asking LSM’s decision.
> 
> I don't understand how it is a problem. Could you please explain?
> procfs/comm is created with S_IRUGO|S_IWUSR permissions. So
> prctl and procfs are simply different interfaces.