linux-kernel - Re: [PATCH v6 0/6] KASAN for arm64

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Date:	Thu, 8 Oct 2015 19:07:45 +0300
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>, Yury <yury.norov@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mark Salter <msalter@...hat.com>,
	Will Deacon <will.deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexey Klimov <klimov.linux@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	David Keitel <dkeitel@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v6 0/6] KASAN for arm64

2015-10-08 18:11 GMT+03:00 Catalin Marinas <catalin.marinas@....com>:
> On Thu, Oct 08, 2015 at 02:09:26PM +0200, Ard Biesheuvel wrote:
>> On 8 October 2015 at 13:23, Andrey Ryabinin <ryabinin.a.a@...il.com> wrote:
>> > On 10/08/2015 02:11 PM, Mark Rutland wrote:
>> >> On Thu, Oct 08, 2015 at 01:36:09PM +0300, Andrey Ryabinin wrote:
>> >>> 2015-10-07 13:04 GMT+03:00 Catalin Marinas <catalin.marinas@....com>:
>> >>>> On Thu, Sep 17, 2015 at 12:38:06PM +0300, Andrey Ryabinin wrote:
>> >>>>> As usual patches available in git
>> >>>>>       git://github.com/aryabinin/linux.git kasan/arm64v6
>> >>>>>
>> >>>>> Changes since v5:
>> >>>>>  - Rebase on top of 4.3-rc1
>> >>>>>  - Fixed EFI boot.
>> >>>>>  - Updated Doc/features/KASAN.
>> >>>>
>> >>>> I tried to merge these patches (apart from the x86 one which is already
>> >>>> merged) but it still doesn't boot on Juno as an EFI application.
>> >>>>
>> >>>
>> >>> 4.3-rc1 was ok and 4.3-rc4 is not. Break caused by 0ce3cc008ec04
>> >>> ("arm64/efi: Fix boot crash by not padding between EFI_MEMORY_RUNTIME
>> >>> regions")
>> >>> It introduced sort() call in efi_get_virtmap().
>> >>> sort() is generic kernel function and it's instrumented, so we crash
>> >>> when KASAN tries to access shadow in sort().
>> >>
>> >> I believe this is solved by Ard's stub isolation series [1,2], which
>> >> will build a stub-specific copy of sort() and various other functions
>> >> (see the arm-deps in [2]).
>> >>
>> >> So long as the stub is not built with ASAN, that should work.
>> >
>> > Thanks, this should help, as we already build the stub without ASAN instrumentation.
>>
>> Indeed. I did not mention instrumentation in the commit log for those
>> patches, but obviously, something like KASAN instrumentation cannot be
>> tolerated in the stub since it makes assumptions about the memory
>> layout
>
> I'll review your latest EFI stub isolation patches and try Kasan again
> on top (most likely tomorrow).

You'd better wait for v7, because kasan patches will need some adjustment.
Since stub is isolated,  we need to handle memcpy vs __memcpy stuff the same
way as we do in x86. Now we also need to #undef memset/memcpy/memmove in ARM64
(just like this was done for x86).

But instead of spreading these #undef across various headers, I will
make a patch (most likely tomorrow)
which will get rid of these #undefs completely (the idea was described
here: https://lkml.org/lkml/2015/9/29/607)
And I'll will send v7 on top of that patch + Ard's work.


> Thanks.
>
> --
> Catalin
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