Commit d8b57bb7 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3aa4b37d

arch/x86/mm/fault.c

+17 −6
Original line number Diff line number Diff line
@@ -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);

}



/*

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