linux-kernel - Re: [PATCH v11 09/24] arm64: move untagged

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Date:   Tue, 27 Nov 2018 17:04:24 +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>,
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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 v11 09/24] arm64: move untagged_addr macro from uaccess.h
 to memory.h

On Fri, Nov 23, 2018 at 6:37 PM, Mark Rutland <mark.rutland@....com> wrote:
> On Mon, Nov 19, 2018 at 06:26:25PM +0100, Andrey Konovalov wrote:
>> Move the untagged_addr() macro from arch/arm64/include/asm/uaccess.h
>> to arch/arm64/include/asm/memory.h to be later reused by KASAN.
>>
>> Also make the untagged_addr() macro accept all kinds of address types
>> (void *, unsigned long, etc.). This allows not to specify type casts in
>> each place where the macro is used. This is done by using __typeof__.
>>
>> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
>> ---
>>  arch/arm64/include/asm/memory.h  | 8 ++++++++
>>  arch/arm64/include/asm/uaccess.h | 7 -------
>>  2 files changed, 8 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
>> index 05fbc7ffcd31..deb95be44392 100644
>> --- a/arch/arm64/include/asm/memory.h
>> +++ b/arch/arm64/include/asm/memory.h
>> @@ -73,6 +73,14 @@
>>  #define KERNEL_START      _text
>>  #define KERNEL_END        _end
>>
>> +/*
>> + * When dealing with data aborts, watchpoints, or instruction traps we may end
>> + * up with a tagged userland pointer. Clear the tag to get a sane pointer to
>> + * pass on to access_ok(), for instance.
>> + */
>> +#define untagged_addr(addr)  \
>> +     (__typeof__(addr))sign_extend64((__u64)(addr), 55)
>
> Minor nits:
>
> * s/__u64/u64/ (or s/__u64/unsigned long/), since this isn't a UAPI
>   header.
>
> * Please move this down into the #ifndef __ASSEMBLY__ block, after we
>   include <linux/bitops.h>, which is necessary for sign_extend64().
>
> With those fixed up, this patch looks sound to me:
>
> Acked-by: Mark Rutland <mark.rutland@....com>
>
> Thanks,
> Mark.

Will do in v12, thanks!

>
>> +
>>  /*
>>   * Generic and tag-based KASAN require 1/8th and 1/16th of the kernel virtual
>>   * address space for the shadow region respectively. They can bloat the stack
>> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
>> index 07c34087bd5e..281a1e47263d 100644
>> --- a/arch/arm64/include/asm/uaccess.h
>> +++ b/arch/arm64/include/asm/uaccess.h
>> @@ -96,13 +96,6 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
>>       return ret;
>>  }
>>
>> -/*
>> - * When dealing with data aborts, watchpoints, or instruction traps we may end
>> - * up with a tagged userland pointer. Clear the tag to get a sane pointer to
>> - * pass on to access_ok(), for instance.
>> - */
>> -#define untagged_addr(addr)          sign_extend64(addr, 55)
>> -
>>  #define access_ok(type, addr, size)  __range_ok(addr, size)
>>  #define user_addr_max                        get_fs
>>
>> --
>> 2.19.1.1215.g8438c0b245-goog
>>
>
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