On 07/10/14 00:26, Dave Hansen wrote:

On 07/09/2014 04:29 AM, Andrey Ryabinin wrote:

quoted

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