linux-kernel - Re: get_arg_page() && ptr

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Message-ID: <20180910172109.GB27005@redhat.com>
Date:   Mon, 10 Sep 2018 19:21:09 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Rik van Riel <riel@...hat.com>, Michal Hocko <mhocko@...e.com>,
        Stanislav Kozina <skozina@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: get_arg_page() && ptr_size accounting

On 09/10, Kees Cook wrote:
>
> On Mon, Sep 10, 2018 at 9:41 AM, Kees Cook <keescook@...omium.org> wrote:
> > On Mon, Sep 10, 2018 at 5:29 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> >> Hi Kees,
> >>
> >> I was thinking about backporting the commit 98da7d08850fb8bde
> >> ("fs/exec.c: account for argv/envp pointers"), but I am not sure
> >> I understand it...
>
> BTW, if you backport that, please get the rest associated with the
> various Stack Clash related weaknesses:

may be...

> da029c11e6b1 exec: Limit arg stack to at most 75% of _STK_LIM

and I have to admit that I do not understand this patch at all, the
changelog explains nothing.

Could you explain what this patch actually prevents from? Especially
now that we have stack_guard_gap?

Oleg.