linux-hardening - Re: [PATCH v8 4/6] x86/entry: Enable random_kstack

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Date:   Wed, 31 Mar 2021 09:50:20 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Kees Cook <keescook@...omium.org>
Cc:     Kees Cook <keescook@...omium.org>,
        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>, Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        Randy Dunlap <rdunlap@...radead.org>,
        kernel-hardening@...ts.openwall.com,
        linux-hardening@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 4/6] x86/entry: Enable random_kstack_offset support

On Tue, Mar 30 2021 at 13:57, Kees Cook wrote:

> Allow for a randomized stack offset on a per-syscall basis, with roughly
> 5-6 bits of entropy, depending on compiler and word size. Since the
> method of offsetting uses macros, this cannot live in the common entry
> code (the stack offset needs to be retained for the life of the syscall,
> which means it needs to happen at the actual entry point).
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>