Re: [PATCH v4 2/3] kasan: skip HW tagging for all kernel thread stacks

[Catalin Marinas]

On Wed, Apr 29, 2026 at 03:57:03PM +0530, Dev Jain wrote:
> From: Muhammad Usama Anjum <usama.anjum@xxxxxxx>
> 
> HW-tag KASAN never checks kernel stacks because stack pointers carry the
> match-all tag, so setting/poisoning tags is pure overhead.
> 
> - Add __GFP_SKIP_KASAN to THREADINFO_GFP so every stack allocator that
>   uses it skips tagging (fork path plus arch users)
> - Add __GFP_SKIP_KASAN to GFP_VMAP_STACK for the fork-specific vmap
>   stacks.
> - When reusing cached vmap stacks, skip kasan_unpoison_range() if HW tags
>   are enabled.
> 
> Software KASAN is unchanged; this only affects tag-based KASAN.
> 
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxx>
> Signed-off-by: Dev Jain <dev.jain@xxxxxxx>

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>