From 1c0e5b24f11707e8c8300060bfdd9ae4ae76611b Mon Sep 17 00:00:00 2001
From: Andrey Konovalov <andreyknvl@google.com>
Date: Thu, 24 Mar 2022 18:10:25 -0700
Subject: [PATCH] kasan: only apply __GFP_ZEROTAGS when memory is zeroed

__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.

Link: https://lkml.kernel.org/r/f4f4593f7f675262d29d07c1938db5bd0cd5e285.1643047180.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 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 0b8225add2e48..c643740b85996 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)
-- 
2.30.2