linux-kernel - Re: [PATCH v4 3/5] stack: Optionally randomize kernel stack offset each syscall

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Message-ID: <202006221425.805E17B67@keescook>
Date:   Mon, 22 Jun 2020 14:26:25 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Elena Reshetova <elena.reshetova@...el.com>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Potapenko <glider@...gle.com>,
        Alexander Popov <alex.popov@...ux.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Jann Horn <jannh@...gle.com>,
        kernel-hardening@...ts.openwall.com,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/5] stack: Optionally randomize kernel stack offset
 each syscall

On Mon, Jun 22, 2020 at 12:40:49PM -0700, Randy Dunlap wrote:
> On 6/22/20 12:31 PM, Kees Cook wrote:
> > This provides the ability for architectures to enable kernel stack base
> > address offset randomization. This feature is controlled by the boot
> > param "randomize_kstack_offset=on/off", with its default value set by
> > CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
> > 
> > Co-developed-by: Elena Reshetova <elena.reshetova@...el.com>
> > Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> > Link: https://lore.kernel.org/r/20190415060918.3766-1-elena.reshetova@intel.com
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> >  Makefile                         |  4 ++++
> >  arch/Kconfig                     | 23 ++++++++++++++++++
> >  include/linux/randomize_kstack.h | 40 ++++++++++++++++++++++++++++++++
> >  init/main.c                      | 23 ++++++++++++++++++
> >  4 files changed, 90 insertions(+)
> >  create mode 100644 include/linux/randomize_kstack.h
> 
> Please add documentation for the new kernel boot parameter to
> Documentation/admin-guide/kernel-parameters.txt.

Oops, yes. Thanks for the reminder!

(I wonder if checkpatch can notice "+early_param" and suggest the Doc
update hmmm)

-- 
Kees Cook