Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965866AbcCPIHc (ORCPT ); Wed, 16 Mar 2016 04:07:32 -0400 Received: from mail.kernel.org ([198.145.29.136]:58991 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965457AbcCPIHT (ORCPT ); Wed, 16 Mar 2016 04:07:19 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "Kirill A. Shutemov" , Andrew Morton , Willy Tarreau , Linus Torvalds , Zefan Li Subject: [PATCH 3.4 006/107] mm: avoid setting up anonymous pages into file mapping Date: Wed, 16 Mar 2016 16:05:00 +0800 Message-Id: <1458115601-5762-6-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1458115541-5712-1-git-send-email-lizf@kernel.org> References: <1458115541-5712-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2601 Lines: 78 From: "Kirill A. Shutemov" 3.4.111-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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 [lizf: Backported to 3.4: adjust context] Signed-off-by: Zefan Li --- mm/memory.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 02aef93..4774579 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3173,6 +3173,14 @@ 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; + + /* 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_SIGSEGV; @@ -3432,6 +3440,9 @@ 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); } @@ -3490,11 +3501,9 @@ 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); } -- 1.9.1