From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755551AbbILX12 (ORCPT ); Sat, 12 Sep 2015 19:27:28 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:9213 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754936AbbILXMK (ORCPT ); Sat, 12 Sep 2015 19:12:10 -0400 Message-Id: <20150912225608.902099888@1wt.eu> User-Agent: quilt/0.63-1 Date: Sun, 13 Sep 2015 00:57:00 +0200 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Kirill A. Shutemov" , Oleg Nesterov , Andrew Morton , Willy Tarreau , Linus Torvalds , Ben Hutchings Subject: [PATCH 2.6.32 54/62] mm: avoid setting up anonymous pages into file mapping MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 In-Reply-To: <08d3b586eb2e764308c3de9ee398a17c@local> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-longterm review patch. If anyone has any objections, please let me know. ------------------ From: "Kirill A. Shutemov" commit 6b7339f4c31ad69c8e9c0b2859276e22cf72176d upstream. Reading page fault handler code I've noticed that under right circumstances kernel would map anonymous pages into file mappings: if the VMA doesn't have vm_ops->fault() and the VMA wasn't fully populated on ->mmap(), kernel would handle page fault to not populated pte with do_anonymous_page(). Let's change page fault handler to use do_anonymous_page() only on anonymous VMA (->vm_ops == NULL) and make sure that the VMA is not shared. For file mappings without vm_ops->fault() or shred VMA without vm_ops, page fault on pte_none() entry would lead to SIGBUS. Signed-off-by: Kirill A. Shutemov Acked-by: Oleg Nesterov Cc: Andrew Morton Cc: Willy Tarreau Signed-off-by: Linus Torvalds [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings (cherry picked from commit e2506476534cff7bb3697fbe0654fdefd101bc80) Signed-off-by: Willy Tarreau --- mm/memory.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 085b068..e36dee2 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2727,6 +2727,10 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, pte_unmap(page_table); + /* File mapping without ->vm_ops ? */ + if (vma->vm_flags & VM_SHARED) + return VM_FAULT_SIGBUS; + /* Check if we need to add a guard page to the stack */ if (check_stack_guard_page(vma, address) < 0) return VM_FAULT_SIGBUS; @@ -2979,6 +2983,9 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma, - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; pte_unmap(page_table); + /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */ + if (!vma->vm_ops->fault) + return VM_FAULT_SIGBUS; return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); } @@ -3037,11 +3044,9 @@ static inline int handle_pte_fault(struct mm_struct *mm, entry = *pte; if (!pte_present(entry)) { if (pte_none(entry)) { - if (vma->vm_ops) { - if (likely(vma->vm_ops->fault)) - return do_linear_fault(mm, vma, address, + if (vma->vm_ops) + return do_linear_fault(mm, vma, address, pte, pmd, flags, entry); - } return do_anonymous_page(mm, vma, address, pte, pmd, flags); } -- 1.7.12.2.21.g234cd45.dirty