Re: [PATCH v6 1/3] fork: Add generic vmalloced stack support

[Ingo Molnar]

* Andy Lutomirski <luto@xxxxxxxxxx> wrote:

> +config VMAP_STACK
> +	default y
> +	bool "Use a virtually-mapped stack"
> +	depends on HAVE_ARCH_VMAP_STACK && !KASAN
> +	---help---
> +	  Enable this if you want the use virtually-mapped kernel stacks
> +	  with guard pages.  This causes kernel stack overflows to be
> +	  caught immediately rather than causing difficult-to-diagnose
> +	  corruption.
> +
> +	  This is presently incompatible with KASAN because KASAN expects
> +	  the stack to map directly to the KASAN shadow map using a formula
> +	  that is incorrect if the stack is in vmalloc space.

Btw., is this KASAN limitation fundamental?

As x86 is going to enable this feature by default, this probably limits KASAN 
utility rather significantly.

Thanks,

	Ingo