From 0927678e0bd57c1853224900d0f710e2f43d85a0 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Thu, 30 Nov 2017 23:06:28 -0500 Subject: [PATCH] mm, thp: Do not make page table dirty unconditionally in follow_trans_huge_pmd() Currently, we unconditionally make page table dirty in follow_trans_huge_pmd(). However, it should be set only in case of write access. This is port of upstream commit: a8f97366452ed491d13cf1e44241bc0b5740b1f0 Orabug: 27165913 Signed-off-by: Kirill A. Shutemov Cc: Michal Hocko Cc: Hugh Dickins Signed-off-by: Linus Torvalds CVE: CVE-2017-1000405 Signed-off-by: Nitin Gupta Reviewed-by: Dhaval Giani --- mm/huge_memory.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index b380af5c779b..97fade84118b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1335,17 +1335,11 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, VM_BUG_ON_PAGE(!PageHead(page), page); if (flags & FOLL_TOUCH) { pmd_t _pmd; - /* - * We should set the dirty bit only for FOLL_WRITE but - * for now the dirty bit in the pmd is meaningless. - * And if the dirty bit will become meaningful and - * we'll only set it with FOLL_WRITE, an atomic - * set_bit will be required on the pmd to set the - * young bit, instead of the current set_pmd_at. - */ - _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); + _pmd = pmd_mkyoung(*pmd); + if (flags & FOLL_WRITE) + _pmd = pmd_mkdirty(_pmd); if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, - pmd, _pmd, 1)) + pmd, _pmd, flags & FOLL_WRITE)) update_mmu_cache_pmd(vma, addr, pmd); } if ((flags & FOLL_POPULATE) && (vma->vm_flags & VM_LOCKED)) { -- 2.50.1