linux-kernel - [PATCH mm 02/11] mm, kasan: use KASAN_TAG

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Date: Thu, 21 Dec 2023 21:04:44 +0100
From: andrey.konovalov@...ux.dev
To: Marco Elver <elver@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	kasan-dev@...glegroups.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH mm 02/11] mm, kasan: use KASAN_TAG_KERNEL instead of 0xff

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

Use the KASAN_TAG_KERNEL marco instead of open-coding 0xff in the mm
code. This macro is provided by include/linux/kasan-tags.h, which does
not include any other headers, so it's safe to include it into mm.h
without causing circular include dependencies.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
---
 include/linux/kasan.h | 1 +
 include/linux/mm.h    | 4 ++--
 mm/page_alloc.c       | 2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index d49e3d4c099e..dbb06d789e74 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -4,6 +4,7 @@
 
 #include <linux/bug.h>
 #include <linux/kasan-enabled.h>
+#include <linux/kasan-tags.h>
 #include <linux/kernel.h>
 #include <linux/static_key.h>
 #include <linux/types.h>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a422cc123a2d..8b2e4841e817 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1815,7 +1815,7 @@ static inline void vma_set_access_pid_bit(struct vm_area_struct *vma)
 
 static inline u8 page_kasan_tag(const struct page *page)
 {
-	u8 tag = 0xff;
+	u8 tag = KASAN_TAG_KERNEL;
 
 	if (kasan_enabled()) {
 		tag = (page->flags >> KASAN_TAG_PGSHIFT) & KASAN_TAG_MASK;
@@ -1844,7 +1844,7 @@ static inline void page_kasan_tag_set(struct page *page, u8 tag)
 static inline void page_kasan_tag_reset(struct page *page)
 {
 	if (kasan_enabled())
-		page_kasan_tag_set(page, 0xff);
+		page_kasan_tag_set(page, KASAN_TAG_KERNEL);
 }
 
 #else /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 7ea9c33320bf..51e85760877a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1059,7 +1059,7 @@ static inline bool should_skip_kasan_poison(struct page *page, fpi_t fpi_flags)
 	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
 		return deferred_pages_enabled();
 
-	return page_kasan_tag(page) == 0xff;
+	return page_kasan_tag(page) == KASAN_TAG_KERNEL;
 }
 
 static void kernel_init_pages(struct page *page, int numpages)
-- 
2.25.1