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Subject: Re: KASAN vs. boot-time switching between 4- and 5-level paging
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From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <e9a395f4-018e-4c8c-2098-170172e438f3@virtuozzo.com>
Date: Tue, 11 Jul 2017 20:29:59 +0300
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To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andy Lutomirski <luto@kernel.org>, Dmitry Vyukov <dvyukov@google.com>, Alexander Potapenko <glider@google.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, "x86@kernel.org" <x86@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@linux.intel.com>, Dave Hansen <dave.hansen@intel.com>, linux-arch <linux-arch@vger.kernel.org>, "linux-mm@kvack.org" <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, kasan-dev <kasan-dev@googlegroups.com>



On 07/11/2017 08:03 PM, Kirill A. Shutemov wrote:
> On Tue, Jul 11, 2017 at 07:45:48PM +0300, Andrey Ryabinin wrote:
>> On 07/11/2017 06:15 PM, Andrey Ryabinin wrote:
>>>
>>> I reproduced this, and this is kasan bug:
>>>
>>>    a??0xffffffff84864897 <x86_early_init_platform_quirks+5>   mov    $0xffffffff83f1d0b8,%rdi 
>>>    a??0xffffffff8486489e <x86_early_init_platform_quirks+12>  movabs $0xdffffc0000000000,%rax 
>>>    a??0xffffffff848648a8 <x86_early_init_platform_quirks+22>  push   %rbp
>>>    a??0xffffffff848648a9 <x86_early_init_platform_quirks+23>  mov    %rdi,%rdx  
>>>    a??0xffffffff848648ac <x86_early_init_platform_quirks+26>  shr    $0x3,%rdx
>>>    a??0xffffffff848648b0 <x86_early_init_platform_quirks+30>  mov    %rsp,%rbp
>>>   >a??0xffffffff848648b3 <x86_early_init_platform_quirks+33>  mov    (%rdx,%rax,1),%al
>>>
>>> we crash on the last move which is a read from shadow
>>
>>
>> Ughh, I forgot about phys_base.
> 
> Thanks! Works for me.
> 
> Can use your Signed-off-by for a [cleaned up version of your] patch?

Sure.

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