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

From: [email-masked] (Dave Hansen)
Date: Thu, 10 Jul 2014 08:55:38 -0700

On 07/10/2014 05:12 AM, Andrey Ryabinin wrote:
> 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);
> }

That's fine, and definitely covers the common cases.  Could you make
sure to call this out explicitly?  Also, there's nothing to _keep_ this
approach working for things out of the direct map, right?  It would just
be a matter of updating the shadow memory to have entries for the other
virtual address ranges.

addr_is_in_mem() is a pretty bad name for what it's doing. :)

I'd probably call it something like kasan_tracks_vaddr().