From 12c9d70bd5056b3ae84746fca973c286f48384cc Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Tue, 2 Feb 2016 16:57:57 -0800 Subject: [PATCH] mm: fix memory leak in copy_huge_pmd() We allocate a pgtable but do not attach it to anything if the PMD is in a DAX VMA, causing it to leak. We certainly try to not free pgtables associated with the huge zero page if the zero page is in a DAX VMA, so I think this is the right solution. This needs to be properly audited. Signed-off-by: Matthew Wilcox Cc: Dan Williams Acked-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/huge_memory.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index c1411961167e..36c070167b71 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -858,7 +858,8 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, return false; entry = mk_pmd(zero_page, vma->vm_page_prot); entry = pmd_mkhuge(entry); - pgtable_trans_huge_deposit(mm, pmd, pgtable); + if (pgtable) + pgtable_trans_huge_deposit(mm, pmd, pgtable); set_pmd_at(mm, haddr, pmd, entry); atomic_long_inc(&mm->nr_ptes); return true; @@ -1036,13 +1037,15 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, spinlock_t *dst_ptl, *src_ptl; struct page *src_page; pmd_t pmd; - pgtable_t pgtable; + pgtable_t pgtable = NULL; int ret; - ret = -ENOMEM; - pgtable = pte_alloc_one(dst_mm, addr); - if (unlikely(!pgtable)) - goto out; + if (!vma_is_dax(vma)) { + ret = -ENOMEM; + pgtable = pte_alloc_one(dst_mm, addr); + if (unlikely(!pgtable)) + goto out; + } dst_ptl = pmd_lock(dst_mm, dst_pmd); src_ptl = pmd_lockptr(src_mm, src_pmd); @@ -1073,7 +1076,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, goto out_unlock; } - if (pmd_trans_huge(pmd)) { + if (!vma_is_dax(vma)) { /* thp accounting separate from pmd_devmap accounting */ src_page = pmd_page(pmd); VM_BUG_ON_PAGE(!PageHead(src_page), src_page); -- 2.20.1