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Date: Thu, 28 Apr 2016 21:36:26 +0200
Message-ID: <CA+rthh8z5HeV93RSrL6-uHyLP-ZMA8=wqG+xyvVn=7=xP4eFbg@mail.gmail.com>
Subject: Re: [PATCH] proc: prevent accessing /proc/<PID>/environ until it's ready
From: Mathias Krause <minipli@googlemail.com>
To: Mateusz Guzik <mguzik@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Emese Revfy <re.emese@gmail.com>, Pax Team <pageexec@freemail.hu>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Cyrill Gorcunov <gorcunov@openvz.org>, Jarod Wilson <jarod@redhat.com>
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On 28 April 2016 at 21:20, Mateusz Guzik <mguzik@redhat.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