[PATCH] arm/kasan:fix the arry size of kasan_early_shadow_pte

From: Hailong liu <hailongliiu@yeah.net>
To: aryabinin@virtuozzo.com
Cc: linux@armlinux.org.uk, glider@google.com, dvyukov@google.com,
	akpm@linux-foundation.org, kasan-dev@googlegroups.com,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, hailongliiu@yeah.net,
	Hailong Liu <liu.hailong6@zte.com.cn>,
	Ziliang Guo <guo.ziliang@zte.com.cn>
Subject: [PATCH] arm/kasan:fix the arry size of kasan_early_shadow_pte
Date: Sat,  9 Jan 2021 12:46:22 +0800	[thread overview]
Message-ID: <20210109044622.8312-1-hailongliiu@yeah.net> (raw)

From: Hailong Liu <liu.hailong6@zte.com.cn>

The size of kasan_early_shadow_pte[] now is PTRS_PER_PTE which defined to
512 for arm architecture. This means that it only covers the prev Linux pte
entries, but not the HWTABLE pte entries for arm.

The reason it works well current is that the symbol kasan_early_shadow_page
immediately following kasan_early_shadow_pte in memory is page aligned,
which makes kasan_early_shadow_pte look like a 4KB size array. But we can't
ensure the order always right with different compiler/linker, nor more bss
symbols be introduced.

We had a test with QEMU + vexpress：put a 512KB-size symbol with attribute
__section(".bss..page_aligned") after kasan_early_shadow_pte, and poison it
after kasan_early_init(). Then enabled CONFIG_KASAN, it failed to boot up.

Signed-off-by: Hailong Liu <liu.hailong6@zte.com.cn>
Signed-off-by: Ziliang Guo <guo.ziliang@zte.com.cn>
---
 include/linux/kasan.h | 6 +++++-
 mm/kasan/init.c       | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 5e0655fb2a6f..fe1ae73ff8b5 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -35,8 +35,12 @@ struct kunit_kasan_expectation {
 #define KASAN_SHADOW_INIT 0
 #endif
 
+#ifndef PTE_HWTABLE_PTRS
+#define PTE_HWTABLE_PTRS 0
+#endif
+
 extern unsigned char kasan_early_shadow_page[PAGE_SIZE];
-extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE];
+extern pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS];
 extern pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD];
 extern pud_t kasan_early_shadow_pud[PTRS_PER_PUD];
 extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index bc0ad208b3a7..7ca0b92d5886 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -64,7 +64,8 @@ static inline bool kasan_pmd_table(pud_t pud)
 	return false;
 }
 #endif
-pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
+pte_t kasan_early_shadow_pte[PTRS_PER_PTE + PTE_HWTABLE_PTRS]
+	__page_aligned_bss;
 
 static inline bool kasan_pte_table(pmd_t pmd)
 {
-- 
2.17.1


