From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753499AbdGMP6y (ORCPT ); Thu, 13 Jul 2017 11:58:54 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:24118 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753208AbdGMP6w (ORCPT ); Thu, 13 Jul 2017 11:58:52 -0400 From: Mike Kravetz To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , Andrea Arcangeli , Michal Hocko , Aaron Lu , "Kirill A . Shutemov" , Vlastimil Babka , Anshuman Khandual , Mike Kravetz Subject: [PATCH] mm/mremap: Fail map duplication attempts for private mappings Date: Thu, 13 Jul 2017 08:58:15 -0700 Message-Id: <1499961495-8063-1-git-send-email-mike.kravetz@oracle.com> X-Mailer: git-send-email 2.7.5 X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org mremap will create a 'duplicate' mapping if old_size == 0 is specified. Such duplicate mappings make no sense for private mappings. If duplication is attempted for a private mapping, mremap creates a separate private mapping unrelated to the original mapping and makes no modifications to the original. This is contrary to the purpose of mremap which should return a mapping which is in some way related to the original. Therefore, return EINVAL in the case where if an attempt is made to duplicate a private mapping. Signed-off-by: Mike Kravetz --- mm/mremap.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/mm/mremap.c b/mm/mremap.c index cd8a1b1..076f506 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -383,6 +383,13 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, if (!vma || vma->vm_start > addr) return ERR_PTR(-EFAULT); + /* + * !old_len is a special case where a mapping is 'duplicated'. + * Do not allow this for private mappings. + */ + if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) + return ERR_PTR(-EINVAL); + if (is_vm_hugetlb_page(vma)) return ERR_PTR(-EINVAL); -- 2.7.5