On Mon, Dec 06, 2021 at 10:43:45PM +0100, andrey.konovalov@xxxxxxxxx wrote:
> From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> __GFP_ZEROTAGS should only be effective if memory is being zeroed.
> Currently, hardware tag-based KASAN violates this requirement.
>
> Fix by including an initialization check along with checking for
> __GFP_ZEROTAGS.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx>
> ---
> mm/kasan/hw_tags.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
> index 0b8225add2e4..c643740b8599 100644
> --- a/mm/kasan/hw_tags.c
> +++ b/mm/kasan/hw_tags.c
> @@ -199,11 +199,12 @@ void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags)
> * page_alloc.c.
> */
> bool init = !want_init_on_free() && want_init_on_alloc(flags);
> + bool init_tags = init && (flags & __GFP_ZEROTAGS);
>
> if (flags & __GFP_SKIP_KASAN_POISON)
> SetPageSkipKASanPoison(page);
>
> - if (flags & __GFP_ZEROTAGS) {
> + if (init_tags) {
You can probably leave this unchanged but add a WARN_ON_ONCE() if !init.
AFAICT there's only a single place where __GFP_ZEROTAGS is passed.
--
Catalin
