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authorShaohua Li <shaohua.li@intel.com>2010-07-27 16:06:28 +0800
committerH. Peter Anvin <hpa@linux.intel.com>2010-08-26 16:00:21 -0700
commit660a293ea9be709b893d371fbc0328fcca33c33a (patch)
tree4ef65b2eebb30e4d61ca685b23bac0678a24852f /arch/x86/mm
parent9b861528a8012e7bc4d1f7bae07395b225331477 (diff)
downloadop-kernel-dev-660a293ea9be709b893d371fbc0328fcca33c33a.zip
op-kernel-dev-660a293ea9be709b893d371fbc0328fcca33c33a.tar.gz
x86, mm: Make spurious_fault check explicitly check the PRESENT 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. [ hpa: added a comment in the code as a warning to janitors ] Signed-off-by: Shaohua Li <shaohua.li@intel.com> LKML-Reference: <1280217988.32400.75.camel@sli10-desk.sh.intel.com> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/mm')
-rw-r--r--arch/x86/mm/fault.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 51f7ee7..caec229 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -872,8 +872,14 @@ spurious_fault(unsigned long error_code, unsigned long address)
if (pmd_large(*pmd))
return spurious_fault_check(error_code, (pte_t *) pmd);
+ /*
+ * Note: don't use pte_present() here, since it returns true
+ * if the _PAGE_PROTNONE bit is set. However, this aliases the
+ * _PAGE_GLOBAL bit, which for kernel pages give false positives
+ * when CONFIG_DEBUG_PAGEALLOC is used.
+ */
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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