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xen: correct race in alloc_p2m_pmd()

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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: Juergen Gross <jgross@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
This commit is contained in:
Juergen Gross 2015-01-12 06:05:08 +01:00 committed by David Vrabel
parent 82c92ed135
commit f241b0b891
1 changed files with 3 additions and 6 deletions
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9
arch/x86/xen/p2m.c
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@ -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 * 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! * 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 *ptechk;
pte_t *pteret = ptep;
pte_t *pte_newpg[PMDS_PER_MID_PAGE]; pte_t *pte_newpg[PMDS_PER_MID_PAGE];
pmd_t *pmdp; pmd_t *pmdp;
unsigned int level; 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) { if (ptechk == pte_pg) {
set_pmd(pmdp, set_pmd(pmdp,
__pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE)); __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE));
if (vaddr == (addr & ~(PMD_SIZE - 1)))
pteret = pte_offset_kernel(pmdp, addr);
pte_newpg[i] = NULL; 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; 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) { if (pte_pg == p2m_missing_pte || pte_pg == p2m_identity_pte) {
/* PMD level is missing, allocate a new one */ /* 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) if (!ptep)
return false; return false;
} }