From patchwork Fri Dec 1 20:10:48 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thadeu Lima de Souza Cascardo X-Patchwork-Id: 843707 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=lists.ubuntu.com (client-ip=91.189.94.19; helo=huckleberry.canonical.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=) Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 3ypQQ14PVMz9sCZ; Sat, 2 Dec 2017 07:11:05 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.86_2) (envelope-from ) id 1eKreB-0003sE-Ib; Fri, 01 Dec 2017 20:10:55 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.86_2) (envelope-from ) id 1eKreA-0003s7-8W for kernel-team@lists.ubuntu.com; Fri, 01 Dec 2017 20:10:54 +0000 Received: from 1.general.cascardo.us.vpn ([10.172.70.58] helo=calabresa.spo.virtua.com.br) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1eKre9-0002cs-IK for kernel-team@lists.ubuntu.com; Fri, 01 Dec 2017 20:10:54 +0000 From: Thadeu Lima de Souza Cascardo To: kernel-team@lists.ubuntu.com Subject: [CVE-2017-1000405 artful] mm, thp: Do not make page table dirty unconditionally in touch_p[mu]d() Date: Fri, 1 Dec 2017 18:10:48 -0200 Message-Id: <20171201201048.8883-1-cascardo@canonical.com> X-Mailer: git-send-email 2.14.1 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: "Kirill A. Shutemov" Currently, we unconditionally make page table dirty in touch_pmd(). It may result in false-positive can_follow_write_pmd(). We may avoid the situation, if we would only make the page table entry dirty if caller asks for write access -- FOLL_WRITE. The patch also changes touch_pud() in the same way. Signed-off-by: Kirill A. Shutemov Cc: Michal Hocko Cc: Hugh Dickins Signed-off-by: Linus Torvalds (cherry picked from commit a8f97366452ed491d13cf1e44241bc0b5740b1f0) CVE-2017-1000405 Signed-off-by: Thadeu Lima de Souza Cascardo Acked-by: Stefan Bader Acked-by: Colin Ian King --- Reproducer has been tested. It "exploits" without the patch. With the patch, it fails. --- mm/huge_memory.c | 36 +++++++++++++----------------------- 1 file changed, 13 insertions(+), 23 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 90731e3b7e58..8b887db33383 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -842,20 +842,15 @@ EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud); #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, - pmd_t *pmd) + pmd_t *pmd, int flags) { 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); } @@ -884,7 +879,7 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, return NULL; if (flags & FOLL_TOUCH) - touch_pmd(vma, addr, pmd); + touch_pmd(vma, addr, pmd, flags); /* * device mapped pages can only be returned if the @@ -973,20 +968,15 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD static void touch_pud(struct vm_area_struct *vma, unsigned long addr, - pud_t *pud) + pud_t *pud, int flags) { pud_t _pud; - /* - * We should set the dirty bit only for FOLL_WRITE but for now - * the dirty bit in the pud 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 pud to - * set the young bit, instead of the current set_pud_at. - */ - _pud = pud_mkyoung(pud_mkdirty(*pud)); + _pud = pud_mkyoung(*pud); + if (flags & FOLL_WRITE) + _pud = pud_mkdirty(_pud); if (pudp_set_access_flags(vma, addr & HPAGE_PUD_MASK, - pud, _pud, 1)) + pud, _pud, flags & FOLL_WRITE)) update_mmu_cache_pud(vma, addr, pud); } @@ -1009,7 +999,7 @@ struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr, return NULL; if (flags & FOLL_TOUCH) - touch_pud(vma, addr, pud); + touch_pud(vma, addr, pud, flags); /* * device mapped pages can only be returned if the @@ -1371,7 +1361,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, page = pmd_page(*pmd); VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); if (flags & FOLL_TOUCH) - touch_pmd(vma, addr, pmd); + touch_pmd(vma, addr, pmd, flags); if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { /* * We don't mlock() pte-mapped THPs. This way we can avoid