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x86: pte_protnone() and pmd_protnone() must check entry is not present

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Since _PAGE_PROTNONE aliases _PAGE_GLOBAL it is only valid if
_PAGE_PRESENT is clear.  Make pte_protnone() and pmd_protnone() check
for this.

This fixes a 64-bit Xen PV guest regression introduced by 8a0516ed8b90
("mm: convert p[te|md]_numa users to p[te|md]_protnone_numa").  Any
userspace process would endlessly fault.

In a 64-bit PV guest, userspace page table entries have _PAGE_GLOBAL set
by the hypervisor.  This meant that any fault on a present userspace
entry (e.g., a write to a read-only mapping) would be misinterpreted as
a NUMA hinting fault and the fault would not be correctly handled,
resulting in the access endlessly faulting.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Vrabel 2015-02-19 13:06:53 +00:00 committed by Linus Torvalds
parent 2b9fb532d4
commit e3a1f6cac1
1 changed files with 4 additions and 2 deletions
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6
arch/x86/include/asm/pgtable.h
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@ -476,12 +476,14 @@ static inline int pmd_present(pmd_t pmd)
*/
static inline int pte_protnone(pte_t pte)
{
return pte_flags(pte) & _PAGE_PROTNONE;
return (pte_flags(pte) & (_PAGE_PROTNONE | _PAGE_PRESENT))
== _PAGE_PROTNONE;
}
static inline int pmd_protnone(pmd_t pmd)
{
return pmd_flags(pmd) & _PAGE_PROTNONE;
return (pmd_flags(pmd) & (_PAGE_PROTNONE | _PAGE_PRESENT))
== _PAGE_PROTNONE;
}
#endif /* CONFIG_NUMA_BALANCING */