Re: [PATCH v4 5/5] arm64: Kconfig: select KASAN_VMALLOC if KANSAN_GENERIC is enabled

[Will Deacon]

On Wed, Mar 24, 2021 at 12:05:22PM +0800, Lecopzer Chen wrote:
> Before this patch, someone who wants to use VMAP_STACK when
> KASAN_GENERIC enabled must explicitly select KASAN_VMALLOC.
> 
> From Will's suggestion [1]:
>   > I would _really_ like to move to VMAP stack unconditionally, and
>   > that would effectively force KASAN_VMALLOC to be set if KASAN is in use
> 
> Because VMAP_STACK now depends on either HW_TAGS or KASAN_VMALLOC if
> KASAN enabled, in order to make VMAP_STACK selected unconditionally,
> we bind KANSAN_GENERIC and KASAN_VMALLOC together.
> 
> Note that SW_TAGS supports neither VMAP_STACK nor KASAN_VMALLOC now,
> so this is the first step to make VMAP_STACK selected unconditionally.

Do you know if anybody is working on this? It's really unfortunate that
we can't move exclusively to VMAP_STACK just because of SW_TAGS KASAN.

That said, what is there to do? As things stand, won't kernel stack
addresses end up using KASAN_TAG_KERNEL?

Will