linux-kernel - Re: Leaking path for set_task

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Message-ID: <20180925183953.GI15710@uranus>
Date:   Tue, 25 Sep 2018 21:39:53 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Tong Zhang <ztong@...edu>
Cc:     adobriyan@...il.com, akpm@...ux-foundation.org,
        viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org,
        linux-security-module@...r.kernel.org, wenbo.s@...sung.com
Subject: Re: Leaking path for set_task_comm

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.