When walking the page tables to resolve an address that points to !present_p*d() entry, huge_pte_offset() returns inconsistent values depending on the level of page table (PUD or PMD).
In the case of a PUD entry, it returns NULL while in the case of a PMD entry, it returns a pointer to the page table entry. Make huge_pte_offset() consistent by always returning NULL on encountering a !present_p*d() entry. Document the behaviour to clarify the expected semantics of this function. Signed-off-by: Punit Agrawal <[email protected]> --- mm/hugetlb.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index bc48ee783dd9..686eb6fa9eb1 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4603,6 +4603,13 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, return pte; } +/* + * huge_pte_offset() - Walk the page table to resolve the hugepage + * entry at address @addr + * + * Return: Pointer to page table entry (PUD or PMD) for address @addr + * or NULL if the entry is not present. + */ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr, unsigned long sz) { @@ -4617,13 +4624,20 @@ pte_t *huge_pte_offset(struct mm_struct *mm, p4d = p4d_offset(pgd, addr); if (!p4d_present(*p4d)) return NULL; + pud = pud_offset(p4d, addr); if (!pud_present(*pud)) return NULL; if (pud_huge(*pud)) return (pte_t *)pud; + pmd = pmd_offset(pud, addr); - return (pte_t *) pmd; + if (!pmd_present(*pmd)) + return NULL; + if (pmd_huge(*pmd)) + return (pte_t *) pmd; + + return NULL; } #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */ -- 2.11.0
