From patchwork Wed Nov 10 23:17:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vivek Goyal X-Patchwork-Id: 12613587 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 458C7C433EF for ; Wed, 10 Nov 2021 23:19:59 +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 B609F6124C for ; Wed, 10 Nov 2021 23:19:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B609F6124C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:38328 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mkwsn-0006Mb-Ez for qemu-devel@archiver.kernel.org; Wed, 10 Nov 2021 18:19:57 -0500 Received: from eggs.gnu.org ([209.51.188.92]:58394) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mkwqk-0003jx-E7 for qemu-devel@nongnu.org; Wed, 10 Nov 2021 18:17:50 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:45758) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mkwqg-0001FY-Tz for qemu-devel@nongnu.org; Wed, 10 Nov 2021 18:17:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636586265; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3T5bD787+9LQh658bYXKz6+jsogqmxJULPNKoKazUno=; b=VqEjN25jlKIyoDBXhNOsd9PlZbL3VZeu0eFDNaFRCzBejjeksod8VBprdP+EWOY2GtogMO ayaxYdRhXoVWzykucA2q9kRqFQ4f6VvRa+s1bJOy7fjmj8cstK37tuDw98ddvO6ZrtFN7x ipzBL+sgJV5IPZNvEf8ygIjO70csSkQ= 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-431-vYdxBWWPOyCJpuqsDHkTHw-1; Wed, 10 Nov 2021 18:17:42 -0500 X-MC-Unique: vYdxBWWPOyCJpuqsDHkTHw-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 C43F51006AA2; Wed, 10 Nov 2021 23:17:41 +0000 (UTC) Received: from horse.redhat.com (unknown [10.22.10.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3AA511973B; Wed, 10 Nov 2021 23:17:41 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 53E982256F0; Wed, 10 Nov 2021 18:17:36 -0500 (EST) From: Vivek Goyal To: qemu-devel@nongnu.org, virtio-fs@redhat.com, dgilbert@redhat.com Subject: [PATCH v3 5/6] virtiofsd: Create new file using O_TMPFILE and set security context Date: Wed, 10 Nov 2021 18:17:27 -0500 Message-Id: <20211110231728.50385-6-vgoyal@redhat.com> In-Reply-To: <20211110231728.50385-1-vgoyal@redhat.com> References: <20211110231728.50385-1-vgoyal@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vgoyal@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=vgoyal@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.699, 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_H2=-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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: chirantan@chromium.org, casey@schaufler-ca.com, omosnace@redhat.com, vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" If guest and host policies can't work with each other, then guest security context (selinux label) needs to be set into an xattr. Say remap guest security.selinux xattr to trusted.virtiofs.security.selinux. That means setting "fscreate" is not going to help as that's ony useful for security.selinux xattr on host. So we need another method which is atomic. Use O_TMPFILE to create new file, set xattr and then linkat() to proper place. But this works only for regular files. So dir, symlinks will continue to be non-atomic. Also if host filesystem does not support O_TMPFILE, we fallback to non-atomic behavior. Signed-off-by: Vivek Goyal --- tools/virtiofsd/passthrough_ll.c | 80 ++++++++++++++++++++++++++++---- 1 file changed, 72 insertions(+), 8 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 7a714b1b5e..4505c0c363 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -2128,14 +2128,29 @@ static int lo_do_open(struct lo_data *lo, struct lo_inode *inode, static int do_create_nosecctx(fuse_req_t req, struct lo_inode *parent_inode, const char *name, mode_t mode, - struct fuse_file_info *fi, int *open_fd) + struct fuse_file_info *fi, int *open_fd, + bool tmpfile) { int err, fd; struct lo_cred old = {}; struct lo_data *lo = lo_data(req); int flags; - flags = fi->flags | O_CREAT | O_EXCL; + if (tmpfile) { + flags = fi->flags | O_TMPFILE; + /* + * Don't use O_EXCL as we want to link file later. Also reset O_CREAT + * otherwise openat() returns -EINVAL. + */ + flags &= ~(O_CREAT | O_EXCL); + + /* O_TMPFILE needs either O_RDWR or O_WRONLY */ + if ((flags & O_ACCMODE) == O_RDONLY) { + flags |= O_RDWR; + } + } else { + flags = fi->flags | O_CREAT | O_EXCL; + } err = lo_change_cred(req, &old, lo->change_umask); if (err) { @@ -2166,7 +2181,7 @@ static int do_create_secctx_fscreate(fuse_req_t req, return err; } - err = do_create_nosecctx(req, parent_inode, name, mode, fi, &fd); + err = do_create_nosecctx(req, parent_inode, name, mode, fi, &fd, false); close_reset_proc_fscreate(fscreate_fd); if (!err) { @@ -2175,6 +2190,44 @@ static int do_create_secctx_fscreate(fuse_req_t req, return err; } +static int do_create_secctx_tmpfile(fuse_req_t req, + struct lo_inode *parent_inode, + const char *name, mode_t mode, + struct fuse_file_info *fi, + const char *secctx_name, int *open_fd) +{ + int err, fd = -1; + struct lo_data *lo = lo_data(req); + char procname[64]; + + err = do_create_nosecctx(req, parent_inode, ".", mode, fi, &fd, true); + if (err) { + return err; + } + + err = fsetxattr(fd, secctx_name, req->secctx.ctx, req->secctx.ctxlen, 0); + if (err) { + err = errno; + goto out; + } + + /* Security context set on file. Link it in place */ + sprintf(procname, "%d", fd); + FCHDIR_NOFAIL(lo->proc_self_fd); + err = linkat(AT_FDCWD, procname, parent_inode->fd, name, + AT_SYMLINK_FOLLOW); + err = err == -1 ? errno : 0; + FCHDIR_NOFAIL(lo->root.fd); + +out: + if (!err) { + *open_fd = fd; + } else if (fd != -1) { + close(fd); + } + return err; +} + static int do_create_secctx_noatomic(fuse_req_t req, struct lo_inode *parent_inode, const char *name, mode_t mode, @@ -2183,7 +2236,7 @@ static int do_create_secctx_noatomic(fuse_req_t req, { int err = 0, fd = -1; - err = do_create_nosecctx(req, parent_inode, name, mode, fi, &fd); + err = do_create_nosecctx(req, parent_inode, name, mode, fi, &fd, false); if (err) { goto out; } @@ -2225,20 +2278,31 @@ static int do_lo_create(fuse_req_t req, struct lo_inode *parent_inode, if (secctx_enabled) { /* * If security.selinux has not been remapped and selinux is enabled, - * use fscreate to set context before file creation. - * Otherwise fallback to non-atomic method of file creation - * and xattr settting. + * use fscreate to set context before file creation. If not, use + * tmpfile method for regular files. Otherwise fallback to + * non-atomic method of file creation and xattr settting. */ if (!mapped_name && lo->use_fscreate) { err = do_create_secctx_fscreate(req, parent_inode, name, mode, fi, open_fd); goto out; + } else if (S_ISREG(mode)) { + err = do_create_secctx_tmpfile(req, parent_inode, name, mode, fi, + ctxname, open_fd); + /* + * If filesystem does not support O_TMPFILE, fallback to non-atomic + * method. + */ + if (!err || err != EOPNOTSUPP) { + goto out; + } } err = do_create_secctx_noatomic(req, parent_inode, name, mode, fi, ctxname, open_fd); } else { - err = do_create_nosecctx(req, parent_inode, name, mode, fi, open_fd); + err = do_create_nosecctx(req, parent_inode, name, mode, fi, open_fd, + false); } out: