linux-kernel - Re: [PATCH] fs/proc/kcore.c: Omit kernel text area for hardened usercopy feature

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Message-ID: <CA+55aFzMXuNPga8A4ABb-fc=BePJ+_r848AAjKLZ8zXF+XZ3LA@mail.gmail.com>
Date:   Wed, 7 Sep 2016 10:24:23 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andi Kleen <andi@...stfloor.org>, Jiri Olsa <jolsa@...hat.com>,
        Jiri Olsa <jolsa@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] fs/proc/kcore.c: Omit kernel text area for hardened
 usercopy feature

On Wed, Sep 7, 2016 at 10:17 AM, Kees Cook <keescook@...omium.org> wrote:
>
> !DEVKMEM is easy to represent, but STRICT_DEVMEM=y gets a little ugly,

I think you can just do

   config STRICT_DEVMEM
        bool "Filter access to /dev/mem" if !HARDENED_USERCOPY
        depends on MMU
        depends on ARCH_HAS_DEVMEM_IS_ALLOWED
        default y

ie you put the "if !HARDENED_USERCOPY" on the *question*, so that if
HARDENED_USERCOPY is set you'll never actually ask it.

Or you just make it go the other way, and make HARDENED_USERCOPY
depend on STRICT_DEVMEM.

                  Linus