linux-kernel - Re: /proc/[pid]/mem write implications

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Date:	Sun, 29 Jan 2012 11:36:21 +0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Bryan Jacobs <its@...ytoremember.us>
CC:	linux-kernel@...r.kernel.org
Subject: Re: /proc/[pid]/mem write implications

On 01/29/2012 09:32 AM, Bryan Jacobs wrote:
> Dear LKML,
>
> I have a few questions on the recent change to allow writing
> to /proc/[pid]/mem. If I understand correctly, the recent
> privilege-escalation vulnerability was fundamentally caused by
> incorrectly verifying that the memory being written to by a process was
> its own. The goal was to only allow processes to write to their own
> memory space - this was deemed harmless.


Well, the more fundamental vulnerability is the check was done in 
write(2) instead of open(2), which leaves a window for exploits.

>
> But I think that allowing arbitrary processes to write to **their own**
> memory via a file descriptor might in itself be problematic. Please,
> help me understand how this is safe.

You will have a sysctl to control if it is writable.

Thanks.
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