linux-kernel - Re: [PATCH 0/2] Support for set_memory

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Message-ID: <CAGXu5j+cr9VizRHgatJURHpE3ZF-YaC0mvtzqfYnOc8TC55A_g@mail.gmail.com>
Date:	Tue, 3 Nov 2015 15:42:43 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Laura Abbott <labbott@...oraproject.org>
Cc:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Xishi Qiu <qiuxishi@...wei.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 0/2] Support for set_memory_* outside of module space

On Tue, Nov 3, 2015 at 1:48 PM, Laura Abbott <labbott@...oraproject.org> wrote:
>
> Hi,
>
> Based on a recent discussion[1] there is interest in having set_memory_* work
> on kernel memory for security and other use cases. This patch adds the
> ability for that to happen behind a kernel option. If this is welcome enough,
> the Kconfig can be dropped. This has been briefly tested but not stress tested.
>
> Thanks,
> Laura
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/382079.html
>
> Laura Abbott (2):
>   arm64: Get existing page protections in split_pmd
>   arm64: Allow changing of attributes outside of modules
>
>  arch/arm64/Kconfig.debug | 11 +++++++
>  arch/arm64/mm/mm.h       |  3 ++
>  arch/arm64/mm/mmu.c      | 11 ++++---
>  arch/arm64/mm/pageattr.c | 74 ++++++++++++++++++++++++++++++++++++++++++++----
>  4 files changed, 88 insertions(+), 11 deletions(-)

This seems like the right thing to have. What's arm64 doing for the
equivalent of x86 and arm's set_kernel_text_* functions? x86 and arm
call their set_memory_* functions, for example. A quick examination
shows mm/mmu.c is just doing it "by hand" in fixup_executable and
mark_rodata_ro? Could those functions use the new set_memory_* ones?

-Kees

-- 
Kees Cook
Chrome OS Security
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