linux-kernel - [PATCH v2 2/3] mm: introduce clear_highpage_kasan

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Message-Id: <4471979b46b2c487787ddcd08b9dc5fedd1b6ffd.1654798516.git.andreyknvl@google.com>
Date:   Thu,  9 Jun 2022 20:18:46 +0200
From:   andrey.konovalov@...ux.dev
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v2 2/3] mm: introduce clear_highpage_kasan_tagged

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

Add a clear_highpage_kasan_tagged() helper that does clear_highpage()
on a page potentially tagged by KASAN.

This helper is used by the following patch.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

---

Changes v1->v2:
- Renamed clear_highpage_tagged() to clear_highpage_kasan_tagged().
- Removed extra empty line in clear_highpage_kasan_tagged().
---
 include/linux/highmem.h | 10 ++++++++++
 mm/page_alloc.c         |  8 ++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 3af34de54330..70b496bbd2d9 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -243,6 +243,16 @@ static inline void clear_highpage(struct page *page)
 	kunmap_local(kaddr);
 }
 
+static inline void clear_highpage_kasan_tagged(struct page *page)
+{
+	u8 tag;
+
+	tag = page_kasan_tag(page);
+	page_kasan_tag_reset(page);
+	clear_highpage(page);
+	page_kasan_tag_set(page, tag);
+}
+
 #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE
 
 static inline void tag_clear_highpage(struct page *page)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 66ef8c310dce..76a02255f57c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1302,12 +1302,8 @@ static void kernel_init_pages(struct page *page, int numpages)
 
 	/* s390's use of memset() could override KASAN redzones. */
 	kasan_disable_current();
-	for (i = 0; i < numpages; i++) {
-		u8 tag = page_kasan_tag(page + i);
-		page_kasan_tag_reset(page + i);
-		clear_highpage(page + i);
-		page_kasan_tag_set(page + i, tag);
-	}
+	for (i = 0; i < numpages; i++)
+		clear_highpage_kasan_tagged(page + i);
 	kasan_enable_current();
 }
 
-- 
2.25.1