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Commit f241b0b8 authored by Juergen Gross's avatar Juergen Gross Committed by David Vrabel
Browse files

xen: correct race in alloc_p2m_pmd() 



When allocating a new pmd for the linear mapped p2m list a check is
done for not introducing another pmd when this just happened on
another cpu. In this case the old pte pointer was returned which
points to the p2m_missing or p2m_identity page. The correct value
would be the pointer to the found new page.

Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
parent 82c92ed1

arch/x86/xen/p2m.c

+3 −6
Original line number Diff line number Diff line
@@ -439,10 +439,9 @@ EXPORT_SYMBOL_GPL(get_phys_to_machine); 
 * a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual

 * pmd. In case of PAE/x86-32 there are multiple pmds to allocate!

 */

static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *ptep, pte_t *pte_pg)

static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)

{

	pte_t *ptechk;

	pte_t *pteret = ptep;

	pte_t *pte_newpg[PMDS_PER_MID_PAGE];

	pmd_t *pmdp;

	unsigned int level;
@@ -476,8 +475,6 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *ptep, pte_t *pte_pg) 
		if (ptechk == pte_pg) {

			set_pmd(pmdp,

				__pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));

			if (vaddr == (addr & ~(PMD_SIZE - 1)))

				pteret = pte_offset_kernel(pmdp, addr);

			pte_newpg[i] = NULL;

		}
@@ -491,7 +488,7 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *ptep, pte_t *pte_pg) 
		vaddr += PMD_SIZE;

	}



	return pteret;

	return lookup_address(addr, &level);

}



/*
@@ -520,7 +517,7 @@ static bool alloc_p2m(unsigned long pfn) 


	if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {

		/* PMD level is missing, allocate a new one */

		ptep = alloc_p2m_pmd(addr, ptep, pte_pg);

		ptep = alloc_p2m_pmd(addr, pte_pg);

		if (!ptep)

			return false;

	}