linux-kernel - [PATCH]x86: make spurious_fault check correct pte bit

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Date:	Tue, 27 Jul 2010 16:06:28 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Huang, Ying" <ying.huang@...el.com>
Subject: [PATCH]x86: make spurious_fault check correct pte bit

pte_present() returns true even present bit isn't set but _PAGE_PROTNONE
(global bit) bit is set. While with CONFIG_DEBUG_PAGEALLOC, free pages have
global bit set but present bit clear. This patch makes we could catch
free pages access with CONFIG_DEBUG_PAGEALLOC enabled.

Signed-off-by: Shaohua Li <shaohua.li@...el.com>

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index f627779..93afd78 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -893,7 +893,7 @@ spurious_fault(unsigned long error_code, unsigned long address)
 		return spurious_fault_check(error_code, (pte_t *) pmd);
 
 	pte = pte_offset_kernel(pmd, address);
-	if (!pte_present(*pte))
+	if (!(pte_flags(*pte) & _PAGE_PRESENT))
 		return 0;
 
 	ret = spurious_fault_check(error_code, pte);



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