Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 30 Mar 2021 17:35:23 +0200
Message-Id: <2dc799014d31ac13fd97bd906bad33e16376fc67.1617118501.git.andreyknvl@google.com>
Mime-Version: 1.0
Subject: [PATCH] kasan: fix conflict with page poisoning
From:   Andrey Konovalov <andreyknvl@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

When page poisoning is enabled, it accesses memory that is marked as
poisoned by KASAN, which leas to false-positive KASAN reports.

Suppress the reports by adding KASAN annotations to unpoison_page()
(poison_page() already has them).

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/page_poison.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/page_poison.c b/mm/page_poison.c
index 65cdf844c8ad..655dc5895604 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -77,12 +77,14 @@ static void unpoison_page(struct page *page)
 	void *addr;
 
 	addr = kmap_atomic(page);
+	kasan_disable_current();
 	/*
 	 * Page poisoning when enabled poisons each and every page
 	 * that is freed to buddy. Thus no extra check is done to
 	 * see if a page was poisoned.
 	 */
-	check_poison_mem(addr, PAGE_SIZE);
+	check_poison_mem(kasan_reset_tag(addr), PAGE_SIZE);
+	kasan_enable_current();
 	kunmap_atomic(addr);
 }
 
-- 
2.31.0.291.g576ba9dcdaf-goog