Re: [PATCH v2 3/4] mm: kasan: Skip page unpoisoning only if __GFP_SKIP_KASAN_UNPOISON

[Vincenzo Frascino <vincenzo.frascino@arm.com>]

On 6/10/22 16:21, Catalin Marinas wrote:
> Currently post_alloc_hook() skips the kasan unpoisoning if the tags will
> be zeroed (__GFP_ZEROTAGS) or __GFP_SKIP_KASAN_UNPOISON is passed. Since
> __GFP_ZEROTAGS is now accompanied by __GFP_SKIP_KASAN_UNPOISON, remove
> the extra check.
> 
> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Peter Collingbourne <pcc@google.com>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> ---
>  mm/page_alloc.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f6ed240870bc..bf45a6aa407a 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2361,7 +2361,7 @@ static inline bool check_new_pcp(struct page *page, unsigned int order)
>  }
>  #endif /* CONFIG_DEBUG_VM */
>  
> -static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
> +static inline bool should_skip_kasan_unpoison(gfp_t flags)
>  {
>  	/* Don't skip if a software KASAN mode is enabled. */
>  	if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
> @@ -2373,12 +2373,10 @@ static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
>  		return true;
>  
>  	/*
> -	 * With hardware tag-based KASAN enabled, skip if either:
> -	 *
> -	 * 1. Memory tags have already been cleared via tag_clear_highpage().
> -	 * 2. Skipping has been requested via __GFP_SKIP_KASAN_UNPOISON.
> +	 * With hardware tag-based KASAN enabled, skip if this has been
> +	 * requested via __GFP_SKIP_KASAN_UNPOISON.
>  	 */
> -	return init_tags || (flags & __GFP_SKIP_KASAN_UNPOISON);
> +	return flags & __GFP_SKIP_KASAN_UNPOISON;
>  }
>  
>  static inline bool should_skip_init(gfp_t flags)
> @@ -2430,7 +2428,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
>  		/* Note that memory is already initialized by the loop above. */
>  		init = false;
>  	}
> -	if (!should_skip_kasan_unpoison(gfp_flags, init_tags)) {
> +	if (!should_skip_kasan_unpoison(gfp_flags)) {
>  		/* Unpoison shadow memory or set memory tags. */
>  		kasan_unpoison_pages(page, order, init);
>  

-- 
Regards,
Vincenzo