[PATCH mm v4 08/39] kasan: only apply __GFP_ZEROTAGS when memory is zeroed

andrey.konovalov
2021-12-20T21:59:18Z

__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@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
---
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) {
int i;

for (i = 0; i != 1 << order; ++i)
--
2.25.1