linux-kernel - Re: [PATCH v10 08/22] kasan, arm64: untag address in __kimg_to_phys and _virt_addr_is

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Date:   Thu, 15 Nov 2018 14:43:02 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Dave Martin <dave.martin@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Ingo Molnar <mingo@...nel.org>,
        Paul Lawrence <paullawrence@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        kasan-dev@...glegroups.com,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
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        Jann Horn <jannh@...gle.com>,
        Mark Brand <markbrand@...gle.com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Vishwath Mohan <vishwath@...gle.com>
Subject: Re: [PATCH v10 08/22] kasan, arm64: untag address in __kimg_to_phys
 and _virt_addr_is_linear

On Wed, Nov 14, 2018 at 8:23 PM, Andrey Konovalov <andreyknvl@...gle.com> wrote:
> On Wed, Nov 7, 2018 at 5:52 PM, Mark Rutland <mark.rutland@....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!