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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,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 04C50C433E0 for ; Wed, 3 Feb 2021 17:15:59 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6CC6F64F87 for ; Wed, 3 Feb 2021 17:15:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CC6F64F87 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:51806 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7Lkz-0007EP-9P for qemu-devel@archiver.kernel.org; Wed, 03 Feb 2021 12:15:57 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34796) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l7Lb3-0003vw-9X for qemu-devel@nongnu.org; Wed, 03 Feb 2021 12:05:43 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:21344) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l7Lb0-0000zD-5Z for qemu-devel@nongnu.org; Wed, 03 Feb 2021 12:05:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612371936; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=iRMTGQefPdMEeA7iSodUerqWQBAn7CQhJSfER/GrT2Q=; b=YHs7fZ41aKeXHlSjL63N65Yv1mN65FRM90s1rSalokI3HczYeMfvo/2K2SHM+CLCkvmxLn NjOE3QPe/jH05SH4wBCZxgKnbbV5XgoxdaadHXVJ6rjgBbRYTsKmJCgJkmmE8WtD392N3Q 1cIv/3zQ2VmjmroLASFq0LvgtE7p50k= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-284-t_W2HPmRNwSTkVe0BUdSTw-1; Wed, 03 Feb 2021 12:05:23 -0500 X-MC-Unique: t_W2HPmRNwSTkVe0BUdSTw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9E2E5BBEE2; Wed, 3 Feb 2021 17:05:22 +0000 (UTC) Received: from localhost (ovpn-115-141.ams2.redhat.com [10.36.115.141]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2745C10013DB; Wed, 3 Feb 2021 17:05:15 +0000 (UTC) Date: Wed, 3 Feb 2021 17:05:14 +0000 From: Stefan Hajnoczi To: Vivek Goyal Subject: Re: [PATCH v4 3/3] virtiofsd: prevent opening of special files (CVE-2020-35517) Message-ID: <20210203170514.GL74271@stefanha-x1.localdomain> References: <20210203113719.83633-1-stefanha@redhat.com> <20210203113719.83633-4-stefanha@redhat.com> <20210203152850.GA3307@redhat.com> <20210203170237.0c98f95f@bahia.lan> <20210203160858.GC3307@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210203160858.GC3307@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="zH41lVBEV8cLJnCl" Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.539, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mszeredi@redhat.com, Daniel Berrange , slp@redhat.com, qemu-devel@nongnu.org, Greg Kurz , "Dr. David Alan Gilbert" , virtio-fs@redhat.com, Alex Xu , P J P , Laszlo Ersek Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --zH41lVBEV8cLJnCl Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Feb 03, 2021 at 11:08:58AM -0500, Vivek Goyal wrote: > On Wed, Feb 03, 2021 at 05:02:37PM +0100, Greg Kurz wrote: > > On Wed, 3 Feb 2021 10:28:50 -0500 > > Vivek Goyal wrote: > >=20 > > > On Wed, Feb 03, 2021 at 11:37:19AM +0000, Stefan Hajnoczi wrote: > > >=20 > > > [..] > > > > @@ -1727,36 +1764,38 @@ static void lo_create(fuse_req_t req, fuse_= ino_t parent, const char *name, > > > > =20 > > > > update_open_flags(lo->writeback, lo->allow_direct_io, fi); > > > > =20 > > > > - fd =3D openat(parent_inode->fd, name, (fi->flags | O_CREAT) & = ~O_NOFOLLOW, > > > > - mode); > > > > + /* Try to create a new file but don't open existing files */ > > > > + fd =3D openat(parent_inode->fd, name, fi->flags | O_CREAT | O_= EXCL, mode); > > > > err =3D fd =3D=3D -1 ? errno : 0; > > > > + > > > > lo_restore_cred(&old); > > > > =20 > > > > - if (!err) { > > > > - ssize_t fh; > > > > - > > > > - pthread_mutex_lock(&lo->mutex); > > > > - fh =3D lo_add_fd_mapping(lo, fd); > > > > - pthread_mutex_unlock(&lo->mutex); > > > > - if (fh =3D=3D -1) { > > > > - close(fd); > > > > - err =3D ENOMEM; > > > > - goto out; > > > > - } > > > > + /* Ignore the error if file exists and O_EXCL was not given */ > > > > + if (err && !(err =3D=3D EEXIST && !(fi->flags & O_EXCL))) { > > >=20 > > > Can this check be simplified to. > > > if (err && (err =3D=3D EEXIST && (fi->flags & O_EXCL)) { > >=20 > > I guess you meant : > >=20 > > if (err && (err !=3D EEXIST || fi->flags & O_EXCL) { >=20 > This sounds correct. I forgot to take into account that if error is > not -EEXIST, we still want to bail out irrespective of O_EXCL. I thought about De Morgan's law too but found the OR expression is not easier to read than the AND expression :(. If you prefer it written this way I can change it though. Stefan --zH41lVBEV8cLJnCl Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmAa18oACgkQnKSrs4Gr c8g1rAf/XJtMnuMThrGmuMVWlc6cAhxTiwwyPYAb+CFiECa2hVjFaoX3paOxWkDG 8PPXQWvUVz1VaCX23CKsvAdX8QNW4RbjUwphBjHnDNkHGviLapu25ZmiNuGplKDx WUUWMwE5BOujGc0rBnvwEP+H9A3Zvdg7SkMcrly97b3pnLCQ97DSmvCbt9dSPegc S4CDg9Y04f9RZeL2t8rKW/G7cNM9RRgDjZzm62s58rLk1jVfn8k1qGyjuScwBezt m/6UKYYV58uSUkbPb8zjXM5F0S1JdJ6RRpG2RW4hfyCg2vmUzAVbQk1IFUaBl/iq 2nEic75Xa+vOtvib6oiFfprvv/QyAg== =CTe+ -----END PGP SIGNATURE----- --zH41lVBEV8cLJnCl--