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From: Andrey Konovalov <andreyknvl@google.com>
Date: Thu, 15 Nov 2018 14:43:02 +0100
Message-ID: <CAAeHK+yaYc4gOxWdvJALwUffAFDVwQe7+4Rwx=Ux936c_LtBFw@mail.gmail.com>
Subject: Re: [PATCH v10 08/22] kasan, arm64: untag address in __kimg_to_phys
 and _virt_addr_is_linear
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To: Mark Rutland <mark.rutland@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>, Alexander Potapenko <glider@google.com>, Dmitry Vyukov <dvyukov@google.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Christoph Lameter <cl@linux.com>, Andrew Morton <akpm@linux-foundation.org>, Nick Desaulniers <ndesaulniers@google.com>, Marc Zyngier <marc.zyngier@arm.com>, Dave Martin <dave.martin@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, "Eric W . Biederman" <ebiederm@xmission.com>, Ingo Molnar <mingo@kernel.org>, Paul Lawrence <paullawrence@google.com>, Geert Uytterhoeven <geert@linux-m68k.org>, Arnd Bergmann <arnd@arndb.de>, "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Kate Stewart <kstewart@linuxfoundation.org>, Mike Rapoport <rppt@linux.vnet.ibm.com>, kasan-dev@googlegroups.com, "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, linux-sparse@vger.kernel.org, Linux Memory Management List <linux-mm@kvack.org>, Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>, Kostya Serebryany <kcc@google.com>, Evgeniy Stepanov <eugenis@google.com>, Lee Smith <Lee.Smith@arm.com>, Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>, Jacob Bramley <Jacob.Bramley@arm.com>, Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>, Jann Horn <jannh@google.com>, Mark Brand <markbrand@google.com>, Chintan Pandya <cpandya@codeaurora.org>, Vishwath Mohan <vishwath@google.com>

On Wed, Nov 14, 2018 at 8:23 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> On Wed, Nov 7, 2018 at 5:52 PM, Mark Rutland <mark.rutland@arm.com> wrote:
>>>  /*
>>> @@ -232,7 +241,7 @@ static inline unsigned long kaslr_offset(void)
>>>  #define __is_lm_address(addr)        (!!((addr) & BIT(VA_BITS - 1)))
>>>
>>>  #define __lm_to_phys(addr)   (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)
>>> -#define __kimg_to_phys(addr) ((addr) - kimage_voffset)
>>> +#define __kimg_to_phys(addr) (KASAN_RESET_TAG(addr) - kimage_voffset)
>>
>> IIUC You need to adjust __lm_to_phys() too, since that could be passed
>> an address from SLAB.
>>
>> Maybe that's done in a later patch, but if so it's confusing to split it
>> out that way. It would be nicer to fix all the *_to_*() helpers in one
>> go.
>
> __lm_to_phys() does & ~PAGE_OFFSET, so it resets the tag by itself. I
> can add an explicit __tag_reset() if you think it makes sense.

Hi Mark,

I think I've addressed all of your comments except for this one. Do
you think it makes sense to add explicit __tag_reset() calls to
__lm_to_phys() and a few other macros, that already set the tag to 0
by doing & ~PAGE_OFFSET?

Thanks!