linux-kernel - Re: [PATCH 1/5] proc: make /proc/*/cmdline go through LSM

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Message-ID: <20180420192546.GA3003@avx2>
Date:   Fri, 20 Apr 2018 22:25:46 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] proc: make /proc/*/cmdline go through LSM

On Thu, Apr 19, 2018 at 05:02:17PM -0700, Andrew Morton wrote:
> On Wed, 21 Feb 2018 22:23:39 +0300 Alexey Dobriyan <adobriyan@...il.com> wrote:
> 
> > /proc/*/cmdline is not different from /proc/*/environ as it accesses
> > target task's memory (and can access the very same region of memory)
> > but it doesn't go through ptrace_may_access() and thus doesn't go through LSM.
> 
> This change can cause existing code to break, no?
> 
> I'd like to see, in the changelog, a full explanation of why this won't
> break any existing setup?

It can. In fact, I'm not sure about this patch anymore.
Original /proc/*/cmdline hook did get_cmdline() which is basically GUP.
It is just nobody said anything when /proc/*/cmdline got rewritten and
security folks aren't bitching about it:

	$ cat /proc/1/cmdline
	init [3]

I'll resend the rest of cmdline changes if they gets broken.