linux-kernel - [PATCH mm v4 08/39] kasan: only apply __GFP

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Date:   Mon, 20 Dec 2021 22:58:23 +0100
From:   andrey.konovalov@...ux.dev
To:     Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH mm v4 08/39] kasan: only apply __GFP_ZEROTAGS when memory is zeroed

From: Andrey Konovalov <andreyknvl@...gle.com>

__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@...gle.com>
Reviewed-by: Alexander Potapenko <glider@...gle.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