linux-kernel - Re: [PATCH v6 13/41] mm: Make pte

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Message-ID: <63f28950.170a0220.aef42.bc00@mx.google.com>
Date:   Sun, 19 Feb 2023 12:40:47 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc:     x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H . J . Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Weijiang Yang <weijiang.yang@...el.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
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        eranian@...gle.com, rppt@...nel.org, jamorris@...ux.microsoft.com,
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        loongarch@...ts.linux.dev, linux-m68k@...ts.linux-m68k.org,
        Michal Simek <monstr@...str.eu>,
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        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
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        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v6 13/41] mm: Make pte_mkwrite() take a VMA

On Sat, Feb 18, 2023 at 01:14:05PM -0800, Rick Edgecombe wrote:
> The x86 Control-flow Enforcement Technology (CET) feature includes a new
> type of memory called shadow stack. This shadow stack memory has some
> unusual properties, which requires some core mm changes to function
> properly.
> 
> One of these unusual properties is that shadow stack memory is writable,
> but only in limited ways. These limits are applied via a specific PTE
> bit combination. Nevertheless, the memory is writable, and core mm code
> will need to apply the writable permissions in the typical paths that
> call pte_mkwrite().
> 
> In addition to VM_WRITE, the shadow stack VMA's will have a flag denoting
> that they are special shadow stack flavor of writable memory. So make
> pte_mkwrite() take a VMA, so that the x86 implementation of it can know to
> create regular writable memory or shadow stack memory.
> 
> Apply the same changes for pmd_mkwrite() and huge_pte_mkwrite().
> 
> No functional change.
> 
> Cc: linux-doc@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-alpha@...r.kernel.org
> Cc: linux-snps-arc@...ts.infradead.org
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-csky@...r.kernel.org
> Cc: linux-hexagon@...r.kernel.org
> Cc: linux-ia64@...r.kernel.org
> Cc: loongarch@...ts.linux.dev
> Cc: linux-m68k@...ts.linux-m68k.org
> Cc: Michal Simek <monstr@...str.eu>
> Cc: Dinh Nguyen <dinguyen@...nel.org>
> Cc: linux-mips@...r.kernel.org
> Cc: openrisc@...ts.librecores.org
> Cc: linux-parisc@...r.kernel.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: linux-riscv@...ts.infradead.org
> Cc: linux-s390@...r.kernel.org
> Cc: linux-sh@...r.kernel.org
> Cc: sparclinux@...r.kernel.org
> Cc: linux-um@...ts.infradead.org
> Cc: xen-devel@...ts.xenproject.org
> Cc: linux-arch@...r.kernel.org
> Cc: linux-mm@...ck.org
> Tested-by: Pengfei Xu <pengfei.xu@...el.com>
> Suggested-by: David Hildenbrand <david@...hat.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>

I'm not an arch maintainer, but it looks like a correct tree-wide
refactor.

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

-- 
Kees Cook