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From: Ye Liu <ye.liu@linux.dev>
To: Pasha Tatashin <pasha.tatashin@soleen.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>
Cc: Ye Liu <liuye@kylinos.cn>, Alexandre Ghiti <alex@ghiti.fr>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org
Subject: [PATCH] mm/page_table_check: add explicit pmd_none check in pte_clear_range
Date: Wed,  5 Aug 2026 20:22:24 +0800	[thread overview]
Message-ID: <20260805122224.2512983-2-ye.liu@linux.dev> (raw)
In-Reply-To: <20260805122224.2512983-1-ye.liu@linux.dev>

From: Ye Liu <liuye@kylinos.cn>

In __page_table_check_pte_clear_range(), the condition to determine
whether to iterate over PTEs only checked pmd_bad() and pmd_leaf().
This relies on the implicit assumption that pmd_none() is always a
subset of pmd_bad() on all architectures supporting PAGE_TABLE_CHECK.

While this assumption currently holds for x86_64, arm64, s390, riscv,
and powerpc, it is an architecture-dependent behavior that may not
hold for future architectures. Add an explicit pmd_none() check to
make the intent clear and avoid calling pte_offset_map() on an empty
PMD, which could lead to undefined behavior.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 mm/page_table_check.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 6ffc536359cd..ed3e1a76f266 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -278,7 +278,7 @@ void __page_table_check_pte_clear_range(struct mm_struct *mm,
 	if (&init_mm == mm)
 		return;
 
-	if (!pmd_bad(pmd) && !pmd_leaf(pmd)) {
+	if (!pmd_none(pmd) && !pmd_bad(pmd) && !pmd_leaf(pmd)) {
 		pte_t *ptep = pte_offset_map(&pmd, addr);
 		unsigned long i;
 
-- 
2.25.1



WARNING: multiple messages have this Message-ID (diff)
From: Ye Liu <ye.liu@linux.dev>
To: Pasha Tatashin <pasha.tatashin@soleen.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>
Cc: Ye Liu <liuye@kylinos.cn>, Alexandre Ghiti <alex@ghiti.fr>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-riscv@lists.infradead.org
Subject: [PATCH] mm/page_table_check: add explicit pmd_none check in pte_clear_range
Date: Wed,  5 Aug 2026 20:22:24 +0800	[thread overview]
Message-ID: <20260805122224.2512983-2-ye.liu@linux.dev> (raw)
In-Reply-To: <20260805122224.2512983-1-ye.liu@linux.dev>

From: Ye Liu <liuye@kylinos.cn>

In __page_table_check_pte_clear_range(), the condition to determine
whether to iterate over PTEs only checked pmd_bad() and pmd_leaf().
This relies on the implicit assumption that pmd_none() is always a
subset of pmd_bad() on all architectures supporting PAGE_TABLE_CHECK.

While this assumption currently holds for x86_64, arm64, s390, riscv,
and powerpc, it is an architecture-dependent behavior that may not
hold for future architectures. Add an explicit pmd_none() check to
make the intent clear and avoid calling pte_offset_map() on an empty
PMD, which could lead to undefined behavior.

Signed-off-by: Ye Liu <liuye@kylinos.cn>
---
 mm/page_table_check.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index 6ffc536359cd..ed3e1a76f266 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -278,7 +278,7 @@ void __page_table_check_pte_clear_range(struct mm_struct *mm,
 	if (&init_mm == mm)
 		return;
 
-	if (!pmd_bad(pmd) && !pmd_leaf(pmd)) {
+	if (!pmd_none(pmd) && !pmd_bad(pmd) && !pmd_leaf(pmd)) {
 		pte_t *ptep = pte_offset_map(&pmd, addr);
 		unsigned long i;
 
-- 
2.25.1


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  reply	other threads:[~2026-08-05 12:23 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-05 12:22 [PATCH] docs/zh_CN: sync page_table_check.rst translation Ye Liu
2026-08-05 12:22 ` Ye Liu [this message]
2026-08-05 12:22   ` [PATCH] mm/page_table_check: add explicit pmd_none check in pte_clear_range Ye Liu
2026-08-05 13:13 ` [PATCH] docs/zh_CN: sync page_table_check.rst translation Dongliang Mu

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