linux-kernel - Re: fs/proc/base.c: text md5sums; tgid vs tid; and INF vs ONE?

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Date:	Wed, 31 Oct 2012 01:23:56 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Arvid Brodin <Arvid.Brodin@...n.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Rientjes <rientjes@...gle.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: fs/proc/base.c: text md5sums; tgid vs tid; and INF vs ONE?

On Tue, Oct 30, 2012 at 09:02:33PM +0000, Arvid Brodin wrote:
> Hi,
> 
> Below is a patch that adds a file /proc/PID/text_md5sum which when read returns the md5
> checksum of a process' text segment. (This would be used e.g. to make sure a process'
> code hasn't been tampered with.)
> 
> However, I have a few questions:
> 
> * What's the difference between the tgid_base_stuff and tid_base_stuff arrays? (One for
> processes and one for the process' threads? I haven't been able to find any info about
> this so I'm guessing.)
> 
> * When should I use the INF ("read") vs the ONE ("show") macro?
> 
> * Any other comments about the code?
> 
> Thanks!

I don't think this increments security by any means. start/end-code are rather
informative fields which are set when program being started, so one can ptrace
it, alloc new exec area, put evil code there, tuneup cs:ip and restore original
program contents, you won't even notice that.
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