linux-kernel - [PATCH] LoongArch: Set correct protection_map[] for VM_NONE/VM

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Message-ID: <20251230075537.3934277-1-chenhuacai@loongson.cn>
Date: Tue, 30 Dec 2025 15:55:37 +0800
From: Huacai Chen <chenhuacai@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev,
	Xuefeng Li <lixuefeng@...ngson.cn>,
	Guo Ren <guoren@...nel.org>,
	Xuerui Wang <kernel@...0n.name>,
	Jiaxun Yang <jiaxun.yang@...goat.com>,
	linux-kernel@...r.kernel.org,
	Huacai Chen <chenhuacai@...ngson.cn>
Subject: [PATCH] LoongArch: Set correct protection_map[] for VM_NONE/VM_SHARED

For 32BIT platform _PAGE_PROTNONE is 0, so set a VMA to be VM_NONE or
VM_SHARED will make pages non-present, then cause Oops with kernel page
fault.

Fix it by set correct protection_map[] for VM_NONE/VM_SHARED, replacing
_PAGE_PROTNONE with _PAGE_PRESENT.

Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
---
 arch/loongarch/mm/cache.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/mm/cache.c b/arch/loongarch/mm/cache.c
index 6be04d36ca07..496916845ff7 100644
--- a/arch/loongarch/mm/cache.c
+++ b/arch/loongarch/mm/cache.c
@@ -160,8 +160,8 @@ void cpu_cache_init(void)
 
 static const pgprot_t protection_map[16] = {
 	[VM_NONE]					= __pgprot(_CACHE_CC | _PAGE_USER |
-								   _PAGE_PROTNONE | _PAGE_NO_EXEC |
-								   _PAGE_NO_READ),
+								   _PAGE_NO_EXEC | _PAGE_NO_READ |
+								   (_PAGE_PROTNONE ? : _PAGE_PRESENT)),
 	[VM_READ]					= __pgprot(_CACHE_CC | _PAGE_VALID |
 								   _PAGE_USER | _PAGE_PRESENT |
 								   _PAGE_NO_EXEC),
@@ -180,8 +180,8 @@ static const pgprot_t protection_map[16] = {
 	[VM_EXEC | VM_WRITE | VM_READ]			= __pgprot(_CACHE_CC | _PAGE_VALID |
 								   _PAGE_USER | _PAGE_PRESENT),
 	[VM_SHARED]					= __pgprot(_CACHE_CC | _PAGE_USER |
-								   _PAGE_PROTNONE | _PAGE_NO_EXEC |
-								   _PAGE_NO_READ),
+								   _PAGE_NO_EXEC | _PAGE_NO_READ |
+								   (_PAGE_PROTNONE ? : _PAGE_PRESENT)),
 	[VM_SHARED | VM_READ]				= __pgprot(_CACHE_CC | _PAGE_VALID |
 								   _PAGE_USER | _PAGE_PRESENT |
 								   _PAGE_NO_EXEC),
-- 
2.47.3