From d8b57bb700a73872fd06b891d7c9bc4cea1a6af4 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 6 Feb 2008 22:39:43 +0100 Subject: [PATCH] x86: make spurious fault handler aware of large mappings In very rare cases, on certain CPUs, we could end up in the spurious fault handler and ignore a large pud/pmd mapping. The resulting pte pointer points into the mapped physical space and dereferencing it will fault recursively. Make the code aware of large mappings and do the permission check on the pmd/pud entry, when a large pud/pmd mapping is detected. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index ad8b9733d6..d8ed4006b3 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -428,6 +428,16 @@ static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs, } #endif +static int spurious_fault_check(unsigned long error_code, pte_t *pte) +{ + if ((error_code & PF_WRITE) && !pte_write(*pte)) + return 0; + if ((error_code & PF_INSTR) && !pte_exec(*pte)) + return 0; + + return 1; +} + /* * Handle a spurious fault caused by a stale TLB entry. This allows * us to lazily refresh the TLB when increasing the permissions of a @@ -457,20 +467,21 @@ static int spurious_fault(unsigned long address, if (!pud_present(*pud)) return 0; + if (pud_large(*pud)) + return spurious_fault_check(error_code, (pte_t *) pud); + pmd = pmd_offset(pud, address); if (!pmd_present(*pmd)) return 0; + if (pmd_large(*pmd)) + return spurious_fault_check(error_code, (pte_t *) pmd); + pte = pte_offset_kernel(pmd, address); if (!pte_present(*pte)) return 0; - if ((error_code & PF_WRITE) && !pte_write(*pte)) - return 0; - if ((error_code & PF_INSTR) && !pte_exec(*pte)) - return 0; - - return 1; + return spurious_fault_check(error_code, pte); } /* -- 2.39.5