From nobody Sat May 18 23:14:50 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1624529965914384.98799333289503; Thu, 24 Jun 2021 03:19:25 -0700 (PDT) Received: from localhost ([::1]:57354 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lwMSC-00025H-PI for importer@patchew.org; Thu, 24 Jun 2021 06:19:24 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33078) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lwMRN-0000up-1Y for qemu-devel@nongnu.org; Thu, 24 Jun 2021 06:18:33 -0400 Received: from us-smtp-delivery-44.mimecast.com ([207.211.30.44]:54918) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lwMRL-0005gH-EI for qemu-devel@nongnu.org; Thu, 24 Jun 2021 06:18:32 -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-551-xxSKPlhDMKOUhdrfxoaDlg-1; Thu, 24 Jun 2021 06:18:21 -0400 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id 72E05824F98; Thu, 24 Jun 2021 10:18:19 +0000 (UTC) Received: from bahia.redhat.com (ovpn-114-242.ams2.redhat.com [10.36.114.242]) by smtp.corp.redhat.com (Postfix) with ESMTP id 230E960E3A; Thu, 24 Jun 2021 10:18:09 +0000 (UTC) X-MC-Unique: xxSKPlhDMKOUhdrfxoaDlg-1 From: Greg Kurz To: qemu-devel@nongnu.org Subject: [PATCH v2] virtiofsd: Don't allow file creation with FUSE_OPEN Date: Thu, 24 Jun 2021 12:18:09 +0200 Message-Id: <20210624101809.48032-1-groug@kaod.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kaod.org Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: softfail client-ip=207.211.30.44; 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: Miklos Szeredi , "Dr. David Alan Gilbert" , Greg Kurz , virtio-fs@redhat.com, Stefan Hajnoczi , Vivek Goyal Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" 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 : /** * 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. But if the client happens to do it anyway, the server ends up passing this flag to open() without the mandatory mode_t 4th argument. Since open() is a variadic function, glibc will happily pass whatever it finds on the stack to the syscall. If this file is compiled with -D_FORTIFY_SOURCE=3D2, glibc will even detect that and abort: *** invalid openat64 call: O_CREAT or O_TMPFILE without mode ***: terminated Specifying O_CREAT with FUSE_OPEN is a protocol violation. Check this in do_open(), print out a message and return an error to the client, EINVAL like we already do when fuse_mbuf_iter_advance() fails. 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. Signed-off-by: Greg Kurz Reviewed-by: Dr. David Alan Gilbert --- v2: - do the check in core FUSE code instead of passthrough_ll (libfuse folks) tools/virtiofsd/fuse_lowlevel.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/virtiofsd/fuse_lowlevel.c b/tools/virtiofsd/fuse_lowleve= l.c index 7fe2cef1eb3b..3d725bcba2ca 100644 --- a/tools/virtiofsd/fuse_lowlevel.c +++ b/tools/virtiofsd/fuse_lowlevel.c @@ -1084,6 +1084,12 @@ static void do_open(fuse_req_t req, fuse_ino_t nodei= d, return; } =20 + /* File creation is handled by do_create() or do_mknod() */ + if (arg->flags & (O_CREAT | O_TMPFILE)) { + fuse_reply_err(req, EINVAL); + return; + } + memset(&fi, 0, sizeof(fi)); fi.flags =3D arg->flags; fi.kill_priv =3D arg->open_flags & FUSE_OPEN_KILL_SUIDGID; --=20 2.31.1