linux-kernel - Re: [RFC/PATCH RESEND -next 01/21] Add kernel address sanitizer infrastructure.

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Date:	Thu, 10 Jul 2014 16:12:35 +0400
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Dave Hansen <dave.hansen@...el.com>, linux-kernel@...r.kernel.org
Cc:	Dmitry Vyukov <dvyukov@...gle.com>,
	Konstantin Serebryany <kcc@...gle.com>,
	Alexey Preobrazhensky <preobr@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Michal Marek <mmarek@...e.cz>,
	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kbuild@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	x86@...nel.org, linux-mm@...ck.org
Subject: Re: [RFC/PATCH RESEND -next 01/21] Add kernel address sanitizer
 infrastructure.

On 07/10/14 00:26, Dave Hansen wrote:
> On 07/09/2014 04:29 AM, Andrey Ryabinin wrote:
>> Address sanitizer dedicates 1/8 of the low memory to the shadow memory and uses direct
>> mapping with a scale and offset to translate a memory address to its corresponding
>> shadow address.
>>
>> Here is function to translate address to corresponding shadow address:
>>
>>      unsigned long kasan_mem_to_shadow(unsigned long addr)
>>      {
>>                 return ((addr - PAGE_OFFSET) >> KASAN_SHADOW_SCALE_SHIFT)
>>                              + kasan_shadow_start;
>>      }
> 
> How does this interact with vmalloc() addresses or those from a kmap()?
> 

It's used only for lowmem:

static inline bool addr_is_in_mem(unsigned long addr)
{
	return likely(addr >= PAGE_OFFSET && addr < (unsigned long)high_memory);
}



static __always_inline void check_memory_region(unsigned long addr,
						size_t size, bool write)
{

	....
	if (!addr_is_in_mem(addr))
		return;
	// check shadow here

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