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Subject[PATCH 09/10] mm: numa: Add paranoid check around pte_protnone_numa
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pte_protnone_numa is only safe to use after VMA checks for PROT_NONE are
complete. Treating a real PROT_NONE PTE as a NUMA hinting fault is going
to result in strangeness so add a check for it. BUG_ON looks like overkill
but if this is hit then it's a serious bug that could result in corruption
so do not even try recovering. It would have been more comprehensive to
check VMA flags in pte_protnone_numa but it would have made the API ugly
just for a debugging check.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/huge_memory.c | 3 +++
mm/memory.c | 3 +++
2 files changed, 6 insertions(+)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index ad2a3ee..8546654 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1273,6 +1273,9 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
bool migrated = false;
int flags = 0;

+ /* A PROT_NONE fault should not end up here */
+ BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
+
ptl = pmd_lock(mm, pmdp);
if (unlikely(!pmd_same(pmd, *pmdp)))
goto out_unlock;
diff --git a/mm/memory.c b/mm/memory.c
index 2ec07a9..7d97af5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3109,6 +3109,9 @@ static int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
bool migrated = false;
int flags = 0;

+ /* A PROT_NONE fault should not end up here */
+ BUG_ON(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)));
+
/*
* The "pte" at this point cannot be used safely without
* validation through pte_unmap_same(). It's of NUMA type but
--
2.1.2


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