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

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Date:	Wed, 4 Nov 2015 10:51:55 -0800
From:	Laura Abbott <labbott@...hat.com>
To:	Kees Cook <keescook@...omium.org>,
	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 11/03/2015 03:42 PM, Kees Cook wrote:
> 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?
>

It looks like mark_rodata_ro could probably use the set_memory_ro. I'll
have to test it out. Longer term, the page table setup code should
probably just be pulled out into a common file.

Do you know the code path in ftrace which would trigger the set_kernel_text_*
If not, I'll go  see if I can figure out if it's implemented yet on arm64.

> -Kees
>

Thanks,
Laura
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