From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754699AbdEESsl (ORCPT ); Fri, 5 May 2017 14:48:41 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:58526 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752792AbdEESda (ORCPT ); Fri, 5 May 2017 14:33:30 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Kirill A. Shutemov" , Oleg Nesterov , Andrew Morton , Willy Tarreau , Linus Torvalds , Amit Pundir Subject: [PATCH 3.18 43/68] mm: avoid setting up anonymous pages into file mapping Date: Fri, 5 May 2017 11:32:28 -0700 Message-Id: <20170505183214.317733386@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170505183212.587141964@linuxfoundation.org> References: <20170505183212.587141964@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.18-stable 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 Signed-off-by: Amit Pundir Signed-off-by: Greg Kroah-Hartman --- mm/memory.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) --- a/mm/memory.c +++ b/mm/memory.c @@ -2629,6 +2629,10 @@ static int do_anonymous_page(struct mm_s 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_SIGSEGV; @@ -3033,6 +3037,9 @@ static int do_linear_fault(struct mm_str - 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; if (!(flags & FAULT_FLAG_WRITE)) return do_read_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); @@ -3198,11 +3205,9 @@ static int handle_pte_fault(struct mm_st entry = ACCESS_ONCE(*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); }