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

[Andrey Konovalov]

On Fri, Jun 10, 2022 at 5:21 PM Catalin Marinas <catalin.marinas at arm.com> 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 at arm.com>
> Cc: Andrey Ryabinin <ryabinin.a.a at gmail.com>
> Cc: Andrey Konovalov <andreyknvl at gmail.com>
> Cc: Peter Collingbourne <pcc at google.com>
> Cc: Vincenzo Frascino <vincenzo.frascino at 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);
>

Reviewed-by: Andrey Konovalov <andreyknvl at gmail.com>