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From:   Kees Cook <keescook@chromium.org>
Date:   Sun, 27 May 2018 07:41:34 -0700
Message-ID: <CAGXu5jK_YfFLKt4vde__bzmhH9SCEz01ET9wyycYkhSSQj5+RA@mail.gmail.com>
Subject: Re: [PATCH] proc: prevent a task from writing on its own /proc/*/mem
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Salvatore Mesoraca <s.mesoraca16@gmail.com>,
        Jann Horn <jannh@google.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        LSM List <linux-security-module@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-mm <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Akinobu Mita <akinobu.mita@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Davidlohr Bueso <dave@stgolabs.net>
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On Sat, May 26, 2018 at 6:33 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> Thus commit f511c0b17b08 "Yes, people use FOLL_FORCE ;)"
>
> Side note, that very sam ecommit f511c0b17b08 is also the explanation for
> why the patch under discussion now seems broken.
>
> People really do use "write to /proc/self/mem" as a way to keep the
> mappings read-only, but have a way to change them when required.

Ah! Yes, that is the commit I was trying to find. Thanks!

-Kees

-- 
Kees Cook
Pixel Security