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From:   andrey.konovalov@linux.dev
To:     Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>
Cc:     Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev@googlegroups.com,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
Subject: [PATCH 2/3] mm: introduce clear_highpage_tagged
Date:   Tue, 31 May 2022 17:43:49 +0200
Message-Id: <d6ba060f18999a00052180c2c10536226b50438a.1654011120.git.andreyknvl@google.com>
In-Reply-To: <4c76a95aff79723de76df146a10888a5a9196faf.1654011120.git.andreyknvl@google.com>
References: <4c76a95aff79723de76df146a10888a5a9196faf.1654011120.git.andreyknvl@google.com>
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From: Andrey Konovalov <andreyknvl@google.com>

Add a clear_highpage_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@google.com>
---
 include/linux/highmem.h | 11 +++++++++++
 mm/page_alloc.c         |  8 ++------
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 3af34de54330..df76a0db7cec 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -243,6 +243,17 @@ static inline void clear_highpage(struct page *page)
 	kunmap_local(kaddr);
 }
 
+static inline void clear_highpage_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..d82ea983a7a3 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_tagged(page + i);
 	kasan_enable_current();
 }
 
-- 
2.25.1