From 7bf07f3d4b4358aa6d99a26d7a0165f1e91c3fcc Mon Sep 17 00:00:00 2001 From: Adam Litke Date: Sat, 3 Sep 2005 15:55:00 -0700 Subject: [PATCH] [PATCH] hugetlb: move stale pte check into huge_pte_alloc() Initial Post (Wed, 17 Aug 2005) This patch moves the if (! pte_none(*pte)) hugetlb_clean_stale_pgtable(pte); logic into huge_pte_alloc() so all of its callers can be immune to the bug described by Kenneth Chen at http://lkml.org/lkml/2004/6/16/246 > It turns out there is a bug in hugetlb_prefault(): with 3 level page table, > huge_pte_alloc() might return a pmd that points to a PTE page. It happens > if the virtual address for hugetlb mmap is recycled from previously used > normal page mmap. free_pgtables() might not scrub the pmd entry on > munmap and hugetlb_prefault skips on any pmd presence regardless what type > it is. Unless I am missing something, it seems more correct to place the check inside huge_pte_alloc() to prevent a the same bug wherever a huge pte is allocated. It also allows checking for this condition when lazily faulting huge pages later in the series. Signed-off-by: Adam Litke Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/mm/hugetlbpage.c | 13 +++++++++++-- mm/hugetlb.c | 2 -- 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/i386/mm/hugetlbpage.c b/arch/i386/mm/hugetlbpage.c index 3b099f32b948..57c486f0e896 100644 --- a/arch/i386/mm/hugetlbpage.c +++ b/arch/i386/mm/hugetlbpage.c @@ -22,12 +22,21 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr) { pgd_t *pgd; pud_t *pud; - pmd_t *pmd = NULL; + pmd_t *pmd; + pte_t *pte = NULL; pgd = pgd_offset(mm, addr); pud = pud_alloc(mm, pgd, addr); pmd = pmd_alloc(mm, pud, addr); - return (pte_t *) pmd; + + if (!pmd) + goto out; + + pte = (pte_t *) pmd; + if (!pte_none(*pte) && !pte_huge(*pte)) + hugetlb_clean_stale_pgtable(pte); +out: + return pte; } pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 6bf720bc662c..901ac523a1c3 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -360,8 +360,6 @@ int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma) ret = -ENOMEM; goto out; } - if (! pte_none(*pte)) - hugetlb_clean_stale_pgtable(pte); idx = ((addr - vma->vm_start) >> HPAGE_SHIFT) + (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));