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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 8614DC07E85 for ; Fri, 7 Dec 2018 03:43:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3733E2082B for ; Fri, 7 Dec 2018 03:43:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3733E2082B 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 S1726103AbeLGDny (ORCPT ); Thu, 6 Dec 2018 22:43:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46018 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726069AbeLGDnx (ORCPT ); Thu, 6 Dec 2018 22:43:53 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 15B3A3003B44; Fri, 7 Dec 2018 03:43:53 +0000 (UTC) Received: from xz-x1 (ovpn-12-222.pek2.redhat.com [10.72.12.222]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A34C951F09; Fri, 7 Dec 2018 03:43:47 +0000 (UTC) Date: Fri, 7 Dec 2018 11:43:45 +0800 From: Peter Xu To: Andrea Arcangeli Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Mike Rapoport , Mike Kravetz , Jann Horn , "Dr. David Alan Gilbert" Subject: Re: [PATCH 1/1] userfaultfd: check VM_MAYWRITE was set after verifying the uffd is registered Message-ID: <20181207034345.GC10726@xz-x1> References: <20181206212028.18726-1-aarcange@redhat.com> <20181206212028.18726-2-aarcange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20181206212028.18726-2-aarcange@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.46]); Fri, 07 Dec 2018 03:43:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 06, 2018 at 04:20:28PM -0500, Andrea Arcangeli wrote: > Calling UFFDIO_UNREGISTER on virtual ranges not yet registered in uffd > could trigger an harmless false positive WARN_ON. Check the vma is > already registered before checking VM_MAYWRITE to shut off the > false positive warning. > > Cc: > Fixes: 29ec90660d68 ("userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas") > Reported-by: syzbot+06c7092e7d71218a2c16@syzkaller.appspotmail.com > Signed-off-by: Andrea Arcangeli > --- > fs/userfaultfd.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c > index cd58939dc977..7a85e609fc27 100644 > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1566,7 +1566,6 @@ 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 Maybe we want to fix this comment too some day: /* * Nothing to do: this vma is already registered into this * userfaultfd and with the right tracking mode too. */ But I don't think it's anything urgent since it's clear it means the other way round and it can potentially be touched up in any further cleanup/fixes of uffd. Acked-by: Peter Xu > @@ -1575,6 +1574,8 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, > if (!vma->vm_userfaultfd_ctx.ctx) > goto skip; > > + WARN_ON(!(vma->vm_flags & VM_MAYWRITE)); > + > if (vma->vm_start > start) > start = vma->vm_start; > vma_end = min(end, vma->vm_end); Thanks, -- Peter Xu