From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B495C43441 for ; Mon, 26 Nov 2018 17:35:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E4E0A20663 for ; Mon, 26 Nov 2018 17:35:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E4E0A20663 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726916AbeK0E3p (ORCPT ); Mon, 26 Nov 2018 23:29:45 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40148 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726253AbeK0E3p (ORCPT ); Mon, 26 Nov 2018 23:29:45 -0500 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2DB1030015EC; Mon, 26 Nov 2018 17:34:57 +0000 (UTC) Received: from sky.random (ovpn-120-160.rdu2.redhat.com [10.10.120.160]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 48017608F3; Mon, 26 Nov 2018 17:34:53 +0000 (UTC) From: Andrea Arcangeli To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Mike Rapoport , Mike Kravetz , Jann Horn , Peter Xu , "Dr. David Alan Gilbert" Subject: [PATCH 3/5] userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas Date: Mon, 26 Nov 2018 12:34:50 -0500 Message-Id: <20181126173452.26955-4-aarcange@redhat.com> In-Reply-To: <20181126173452.26955-1-aarcange@redhat.com> References: <20181126173452.26955-1-aarcange@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 26 Nov 2018 17:34:57 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org After the VMA to register the uffd onto is found, check that it has VM_MAYWRITE set before allowing registration. This way we inherit all common code checks before allowing to fill file holes in shmem and hugetlbfs with UFFDIO_COPY. The userfaultfd memory model is not applicable for readonly files unless it's a MAP_PRIVATE. Reviewed-by: Mike Rapoport Reviewed-by: Hugh Dickins Reported-by: Jann Horn Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support") Fixes: ff62a3421044 ("hugetlb: implement memfd sealing") Cc: stable@vger.kernel.org Signed-off-by: Andrea Arcangeli --- fs/userfaultfd.c | 15 +++++++++++++++ mm/userfaultfd.c | 15 ++++++--------- 2 files changed, 21 insertions(+), 9 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 356d2b8568c1..cd58939dc977 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1361,6 +1361,19 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, ret = -EINVAL; if (!vma_can_userfault(cur)) goto out_unlock; + + /* + * UFFDIO_COPY will fill file holes even without + * PROT_WRITE. This check enforces that if this is a + * MAP_SHARED, the process has write permission to the backing + * file. If VM_MAYWRITE is set it also enforces that on a + * MAP_SHARED vma: there is no F_WRITE_SEAL and no further + * F_WRITE_SEAL can be taken until the vma is destroyed. + */ + ret = -EPERM; + if (unlikely(!(cur->vm_flags & VM_MAYWRITE))) + goto out_unlock; + /* * If this vma contains ending address, and huge pages * check alignment. @@ -1406,6 +1419,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx, BUG_ON(!vma_can_userfault(vma)); BUG_ON(vma->vm_userfaultfd_ctx.ctx && vma->vm_userfaultfd_ctx.ctx != ctx); + WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); /* * Nothing to do: this vma is already registered into this @@ -1552,6 +1566,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, cond_resched(); BUG_ON(!vma_can_userfault(vma)); + WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); /* * Nothing to do: this vma is already registered into this diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 471b6457f95f..43cf314cfddd 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -205,8 +205,9 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, if (!dst_vma || !is_vm_hugetlb_page(dst_vma)) goto out_unlock; /* - * Only allow __mcopy_atomic_hugetlb on userfaultfd - * registered ranges. + * Check the vma is registered in uffd, this is + * required to enforce the VM_MAYWRITE check done at + * uffd registration time. */ if (!dst_vma->vm_userfaultfd_ctx.ctx) goto out_unlock; @@ -459,13 +460,9 @@ static __always_inline ssize_t __mcopy_atomic(struct mm_struct *dst_mm, if (!dst_vma) goto out_unlock; /* - * Be strict and only allow __mcopy_atomic on userfaultfd - * registered ranges to prevent userland errors going - * unnoticed. As far as the VM consistency is concerned, it - * would be perfectly safe to remove this check, but there's - * no useful usage for __mcopy_atomic ouside of userfaultfd - * registered ranges. This is after all why these are ioctls - * belonging to the userfaultfd and not syscalls. + * Check the vma is registered in uffd, this is required to + * enforce the VM_MAYWRITE check done at uffd registration + * time. */ if (!dst_vma->vm_userfaultfd_ctx.ctx) goto out_unlock;