linux-kernel - Re: [RFC PATCH 08/14] security: introduce CONFIG_SLAB

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Message-ID: <202309151407.2FD7F80B@keescook>
Date:   Fri, 15 Sep 2023 14:07:10 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matteo Rizzo <matteorizzo@...gle.com>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, vbabka@...e.cz,
        roman.gushchin@...ux.dev, 42.hyeyoo@...il.com,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-hardening@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        corbet@....net, luto@...nel.org, peterz@...radead.org,
        jannh@...gle.com, evn@...gle.com, poprdi@...gle.com,
        jordyzomer@...gle.com
Subject: Re: [RFC PATCH 08/14] security: introduce CONFIG_SLAB_VIRTUAL

On Fri, Sep 15, 2023 at 10:59:27AM +0000, Matteo Rizzo wrote:
> From: Jann Horn <jannh@...gle.com>
> 
> SLAB_VIRTUAL is a mitigation for the SLUB allocator which prevents reuse
> of virtual addresses across different slab caches and therefore makes
> some types of use-after-free bugs unexploitable.
> 
> SLAB_VIRTUAL is incompatible with KASAN and we believe it's not worth
> adding support for it. This is because SLAB_VIRTUAL and KASAN are aimed
> at two different use cases: KASAN is meant for catching bugs as early as
> possible in debug/fuzz/testing builds, and it's not meant to be used in
> production. SLAB_VIRTUAL on the other hand is an exploit mitigation that
> doesn't attempt to highlight bugs but instead tries to make them
> unexploitable. It doesn't make sense to enable it in debugging builds or
> during fuzzing, and instead we expect that it will be enabled in
> production kernels.
> 
> SLAB_VIRTUAL is not currently compatible with KFENCE, removing this
> limitation is future work.
> 
> Signed-off-by: Jann Horn <jannh@...gle.com>

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

-- 
Kees Cook