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Date: Wed, 8 Feb 2012 16:15:16 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: WANG Cong <xiyou.wangcong@gmail.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: + proc-clean-up-proc-pid-environ-handling.patch added to -mm
	tree
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> From: Cong Wang <xiyou.wangcong@gmail.com>
> Subject: proc: clean up /proc/<pid>/environ handling
>
> Similar to e268337dfe2 ("proc: clean up and fix /proc/<pid>/mem
> handling"),

and has the same problem,

> move the check of permission to open(), this will simplify
> read() code.

but allows to kill the system trivially.

Please look at 6d08f2c7139790c268820a2e590795cb8333181a
"proc: make sure mem_open() doesn't pin the target's memory"

Oleg.