linux-kernel - Re: [PATCH] Enable writing to /proc/PID/mem.

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Date:	Thu,  3 Mar 2011 11:22:59 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Stephen Wilson <wilsons@...rt.ca>
Cc:	kosaki.motohiro@...fujitsu.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	David Rientjes <rientjes@...gle.com>,
	Nick Piggin <npiggin@...nel.dk>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Enable writing to /proc/PID/mem.

> For a long time /proc/PID/mem has provided a read-only interface, at least since
> 2.4.0.  However, a write capability has existed "forever" in tree via the
> function mem_write, disabled with an #ifdef along with the comment "this is a
> security hazard".  Charles Wright, back in 2006, gave some history on the
> subject:
> 
>     http://lkml.org/lkml/2006/3/10/224
> 
> Later, in commit 638fa202c, Roland McGrath updated mem_write to call
> check_mem_permission which ensures an identical security policy for
> /proc/PID/mem as for ptrace().  IOW, the proc interface provides a simpler, more
> efficient, but otherwise equivalent mechanism for probing a processes memory as
> available via ptrace.
> 
> There is no longer a security hazard and the world can safely use read/write
> instead of ptrace PEEK/POKE's.  Remove the #ifdef.
> 
> Signed-off-by: Stephen Wilson <wilsons@...rt.ca>

I haven't found any problem in this patch. But, I really believe we need
to understand why it was marked "security hazard". Al, I guess you know it,
right? So, can you please talk us your mention?



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