linux-hardening - Re: [PATCH v4 22/26] arm64: mm: move ro_after

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Date:   Mon, 13 Jun 2022 19:16:15 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-hardening@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Brown <broonie@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v4 22/26] arm64: mm: move ro_after_init section into the
 data segment

On Mon, 13 Jun 2022 at 19:00, Kees Cook <keescook@...omium.org> wrote:
>
> On Mon, Jun 13, 2022 at 04:45:46PM +0200, Ard Biesheuvel wrote:
> > Currently, the ro_after_init sections sits right in the middle of the
> > text/rodata/inittext segment, making it difficult to map any of those
> > non-writable during early boot. So instead, move it to the start of
> > .data, and update the init sequences so that the section is remapped
> > read-only once startup completes.
> >
> > Note that this moves the entire HYP data section into .data as well -
> > this likely needs to remain as a single block for now, but could perhaps
> > split into a .rodata and .data..ro_after_init section later.
>
> If I'm reading this correctly, this means that .data..ro_after_init now
> lives between .data and .rodata?
>

No, between .initdata and .data

> Do the various LKDTM tests still pass after this change?
>

Good question, I'll check.

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