linux-hardening - Re: [RFC PATCH 04/14] mm: use virt_to_slab instead of folio

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Date:   Fri, 15 Sep 2023 13:59:22 -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 04/14] mm: use virt_to_slab instead of folio_slab

On Fri, Sep 15, 2023 at 10:59:23AM +0000, Matteo Rizzo wrote:
> From: Jann Horn <jannh@...gle.com>
> 
> This is refactoring in preparation for the introduction of SLAB_VIRTUAL
> which does not implement folio_slab.
> 
> With SLAB_VIRTUAL there is no longer a 1:1 correspondence between slabs
> and pages of physical memory used by the slab allocator. There is no way
> to look up the slab which corresponds to a specific page of physical
> memory without iterating over all slabs or over the page tables. Instead
> of doing that, we can look up the slab starting from its virtual address
> which can still be performed cheaply with both SLAB_VIRTUAL enabled and
> disabled.
> 
> Signed-off-by: Jann Horn <jannh@...gle.com>

Refactoring continues to track.

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

-- 
Kees Cook