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 <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index ad8b973..d8ed400 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -428,6 +428,16 @@
}
#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 @@
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);
}
/*