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Commit 1063711b authored by Andi Kleen's avatar Andi Kleen Committed by Thomas Gleixner
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x86/mm/kmmio: Make the tracer robust against L1TF 



The mmio tracer sets io mapping PTEs and PMDs to non present when enabled
without inverting the address bits, which makes the PTE entry vulnerable
for L1TF.

Make it use the right low level macros to actually invert the address bits
to protect against L1TF.

In principle this could be avoided because MMIO tracing is not likely to be
enabled on production machines, but the fix is straigt forward and for
consistency sake it's better to get rid of the open coded PTE manipulation.

Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 958f79b9

arch/x86/mm/kmmio.c

+15 −10
Original line number Diff line number Diff line
@@ -126,24 +126,29 @@ static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long addr) 


static void clear_pmd_presence(pmd_t *pmd, bool clear, pmdval_t *old)

{

	pmd_t new_pmd;

	pmdval_t v = pmd_val(*pmd);

	if (clear) {

		*old = v & _PAGE_PRESENT;

		v &= ~_PAGE_PRESENT;

	} else	/* presume this has been called with clear==true previously */

		v |= *old;

	set_pmd(pmd, __pmd(v));

		*old = v;

		new_pmd = pmd_mknotpresent(*pmd);

	} else {

		/* Presume this has been called with clear==true previously */

		new_pmd = __pmd(*old);

	}

	set_pmd(pmd, new_pmd);

}



static void clear_pte_presence(pte_t *pte, bool clear, pteval_t *old)

{

	pteval_t v = pte_val(*pte);

	if (clear) {

		*old = v & _PAGE_PRESENT;

		v &= ~_PAGE_PRESENT;

	} else	/* presume this has been called with clear==true previously */

		v |= *old;

	set_pte_atomic(pte, __pte(v));

		*old = v;

		/* Nothing should care about address */

		pte_clear(&init_mm, 0, pte);

	} else {

		/* Presume this has been called with clear==true previously */

		set_pte_atomic(pte, __pte(*old));

	}

}



static int clear_page_presence(struct kmmio_fault_page *f, bool clear)