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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C48E8C48BDF for ; Fri, 18 Jun 2021 08:22:04 +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 421C261026 for ; Fri, 18 Jun 2021 08:22:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 421C261026 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kaod.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49348 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lu9lL-0006s2-13 for qemu-devel@archiver.kernel.org; Fri, 18 Jun 2021 04:22:03 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:38664) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lu9ka-0006C3-1M for qemu-devel@nongnu.org; Fri, 18 Jun 2021 04:21:16 -0400 Received: from us-smtp-delivery-44.mimecast.com ([205.139.111.44]:28064) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lu9kY-000503-2d for qemu-devel@nongnu.org; Fri, 18 Jun 2021 04:21:15 -0400 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-550-11GOmZ0JMy2doLTszF75PQ-1; Fri, 18 Jun 2021 04:21:08 -0400 X-MC-Unique: 11GOmZ0JMy2doLTszF75PQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5B83A100C61B; Fri, 18 Jun 2021 08:21:07 +0000 (UTC) Received: from bahia.lan (ovpn-112-153.ams2.redhat.com [10.36.112.153]) by smtp.corp.redhat.com (Postfix) with ESMTP id B986719D61; Fri, 18 Jun 2021 08:20:58 +0000 (UTC) Date: Fri, 18 Jun 2021 10:20:57 +0200 From: Greg Kurz To: Vivek Goyal Subject: Re: [PATCH] virtiofsd: Don't allow file creation with FUSE_OPEN Message-ID: <20210618102057.21e901fa@bahia.lan> In-Reply-To: <20210618014007.GA1219970@redhat.com> References: <20210617141518.304659-1-groug@kaod.org> <20210618014007.GA1219970@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kaod.org Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Received-SPF: softfail client-ip=205.139.111.44; envelope-from=groug@kaod.org; helo=us-smtp-delivery-44.mimecast.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_SOFTFAIL=0.665 autolearn=no 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: virtio-fs@redhat.com, Miklos Szeredi , qemu-devel@nongnu.org, Stefan Hajnoczi , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, 17 Jun 2021 21:40:07 -0400 Vivek Goyal wrote: > On Thu, Jun 17, 2021 at 04:15:18PM +0200, Greg Kurz wrote: > > A well behaved FUSE client uses FUSE_CREATE to create files. It isn't > > supposed to pass O_CREAT along a FUSE_OPEN request, as documented in > > the "fuse_lowlevel.h" header : > >=20 > > /** > > * Open a file > > * > > * Open flags are available in fi->flags. The following rules > > * apply. > > * > > * - Creation (O_CREAT, O_EXCL, O_NOCTTY) flags will be > > * filtered out / handled by the kernel. > >=20 > > But if it does anyway, virtiofsd crashes with: > >=20 > > *** invalid openat64 call: O_CREAT or O_TMPFILE without mode ***: termi= nated >=20 This is also the consequence of virtiofsd being compiled with -D_FORTIFY_SOURCE=3D2. Without that, no abort but arbitrary data is passed as mode_t argument to the openat() syscall instead. > So did you hit this error with current fuse client. If yes, that means > client needs fixing as well? >=20 I've patched the client to cause this: --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -28,6 +28,7 @@ static int fuse_send_open(struct fuse_mount *fm, u64 node= id, =20 memset(&inarg, 0, sizeof(inarg)); inarg.flags =3D open_flags & ~(O_CREAT | O_EXCL | O_NOCTTY); + if (opcode =3D=3D FUSE_OPEN) inarg.flags |=3D O_TMPFILE; if (!fm->fc->atomic_o_trunc) inarg.flags &=3D ~O_TRUNC; > Or you are doing this fix based on comment in fuse_lowlevel.h. >=20 > I am wondering why this protocl restriction is there that open() > path should not be able to honor O_CREAT. >=20 It isn't a protocol restriction IMHO. The distinction between file creation and file opening has always been there since the start. Older versions of the protocol would send FUSE_MKNOD to create a file and then send FUSE_OPEN to open it. Because this was racy, FUSE_CREATE was introduced at some point to do both operations atomically. Question is : what would be the semantics of O_CREAT in FUSE_OPEN ? > Vivek >=20 > >=20 > > This is because virtiofsd ends up passing this flag to openat() without > > passing a mode_t 4th argument which is mandatory with O_CREAT, and glib= c > > aborts. > >=20 > > The offending path is: > >=20 > > lo_open() > > lo_do_open() > > lo_inode_open() > >=20 > > Other callers of lo_inode_open() only pass O_RDWR and lo_create() > > passes a valid fd to lo_do_open() which thus doesn't even call > > lo_inode_open() in this case. > >=20 > > Specifying O_CREAT with FUSE_OPEN is a protocol violation. Check this > > in lo_open() and return an error to the client : EINVAL since this is > > already what glibc returns with other illegal flag combinations. > >=20 > > The FUSE filesystem doesn't currently support O_TMPFILE, but the very > > same would happen if O_TMPFILE was passed in a FUSE_OPEN request. Check > > that as well. > >=20 > > Signed-off-by: Greg Kurz > > --- > > tools/virtiofsd/passthrough_ll.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > >=20 > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthr= ough_ll.c > > index 49c21fd85570..14f62133131c 100644 > > --- a/tools/virtiofsd/passthrough_ll.c > > +++ b/tools/virtiofsd/passthrough_ll.c > > @@ -2145,6 +2145,12 @@ static void lo_open(fuse_req_t req, fuse_ino_t i= no, struct fuse_file_info *fi) > > return; > > } > > =20 > > + /* File creation is handled by lo_create() */ > > + if (fi->flags & (O_CREAT | O_TMPFILE)) { > > + fuse_reply_err(req, EINVAL); > > + return; > > + } > > + > > err =3D lo_do_open(lo, inode, -1, fi); > > lo_inode_put(lo, &inode); > > if (err) { > > --=20 > > 2.31.1 > >=20 >=20