linux-kernel - Re: [PATCH v2 1/2] stack: Introduce CONFIG_RANDOMIZE_KSTACK

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Message-ID: <202201311314.2978E80C05@keescook>
Date:   Mon, 31 Jan 2022 13:14:58 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Marco Elver <elver@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Alexander Potapenko <glider@...gle.com>, llvm@...ts.linux.dev,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] stack: Introduce CONFIG_RANDOMIZE_KSTACK_OFFSET

On Mon, Jan 31, 2022 at 10:05:20AM +0100, Marco Elver wrote:
> The randomize_kstack_offset feature is unconditionally compiled in when
> the architecture supports it.
> 
> To add constraints on compiler versions, we require a dedicated Kconfig
> variable. Therefore, introduce RANDOMIZE_KSTACK_OFFSET.
> 
> Furthermore, this option is now also configurable by EXPERT kernels:
> while the feature is supposed to have zero performance overhead when
> disabled, due to its use of static branches, there are few cases where
> giving a distribution the option to disable the feature entirely makes
> sense. For example, in very resource constrained environments, which
> would never enable the feature to begin with, in which case the
> additional kernel code size increase would be redundant.
> 
> Signed-off-by: Marco Elver <elver@...gle.com>

Acked-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook