linux-kernel - Re: [PATCH] proc: prevent accessing /proc/<PID>/environ until it's ready

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Message-ID: <CA+rthh8z5HeV93RSrL6-uHyLP-ZMA8=wqG+xyvVn=7=xP4eFbg@mail.gmail.com>
Date:	Thu, 28 Apr 2016 21:36:26 +0200
From:	Mathias Krause <minipli@...glemail.com>
To:	Mateusz Guzik <mguzik@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Emese Revfy <re.emese@...il.com>,
	Pax Team <pageexec@...email.hu>,
	Al Viro <viro@...iv.linux.org.uk>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Jarod Wilson <jarod@...hat.com>
Subject: Re: [PATCH] proc: prevent accessing /proc/<PID>/environ until it's ready

On 28 April 2016 at 21:20, Mateusz Guzik <mguzik@...hat.com> wrote:
> In this case get_cmdline in mm/util.c should also be patched for
> completness. It tests for arg_end, but later accesses env_end.

But it'll do this only when argv[] was modified from what the kernel
initially wrote, which, in turn, either requires the process to have
started executing and messing with it's own argv[] or another process
poking at it via ptrace(). In the former case env_end will be non-zero
already and I don't know if the latter case is actually possible, i.e.
if one can already attach to a process this early. If one can, then
yes, that place needs to be modified, too.

Thanks,
Mathias