From patchwork Fri May 1 19:14:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Dr. David Alan Gilbert" X-Patchwork-Id: 283596 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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, 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 33945C47253 for ; Fri, 1 May 2020 19:18:52 +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 F16392173E for ; Fri, 1 May 2020 19:18:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="caXAjSV9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F16392173E 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]:43116 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jUbBT-0002yT-3i for qemu-devel@archiver.kernel.org; Fri, 01 May 2020 15:18:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33400) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jUb87-0006eB-MU for qemu-devel@nongnu.org; Fri, 01 May 2020 15:15:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.90_1) (envelope-from ) id 1jUb85-00007b-Ol for qemu-devel@nongnu.org; Fri, 01 May 2020 15:15:23 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:27216 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jUb85-000052-9h for qemu-devel@nongnu.org; Fri, 01 May 2020 15:15:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588360519; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=zteTfA7zZtn3nnO6RlPjKvIiRXQcvA5/CVIFdyzVXno=; b=caXAjSV9x6NYWN7ALD4iwU8hsqmvmX8KCYth+sJi/34VEB+M0dH9pSM8xMQ2Kb23k/56RO pvSLXtyosQB8/vksyAJUrruzVtKUXouz+D2IApns1hVRc6xt/8Y/GqXgCjFM/SgbcaMMpE sfzsAvFDx0DzksMR8Yh3YaiGWJkpSYc= 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-328-u0gqWlE6N6yBmIxjBT_JoA-1; Fri, 01 May 2020 15:15:17 -0400 X-MC-Unique: u0gqWlE6N6yBmIxjBT_JoA-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 81A5D18FE870; Fri, 1 May 2020 19:15:16 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-112-191.ams2.redhat.com [10.36.112.191]) by smtp.corp.redhat.com (Postfix) with ESMTP id 486E31001B2C; Fri, 1 May 2020 19:15:15 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com, yavrahami@paloaltonetworks.com, mszeredi@redhat.com, mreitz@redhat.com Subject: [PULL 3/6] virtiofsd: jail lo->proc_self_fd Date: Fri, 1 May 2020 20:14:57 +0100 Message-Id: <20200501191500.126432-4-dgilbert@redhat.com> In-Reply-To: <20200501191500.126432-1-dgilbert@redhat.com> References: <20200501191500.126432-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=205.139.110.61; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/01 12:40:15 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" From: Miklos Szeredi While it's not possible to escape the proc filesystem through lo->proc_self_fd, it is possible to escape to the root of the proc filesystem itself through "../..". Use a temporary mount for opening lo->proc_self_fd, that has it's root at /proc/self/fd/, preventing access to the ancestor directories. Signed-off-by: Miklos Szeredi Message-Id: <20200429124733.22488-1-mszeredi@redhat.com> Reviewed-by: Stefan Hajnoczi Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_ll.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index f7b9c1d20c..d7a6474b6e 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -2536,6 +2536,8 @@ static void print_capabilities(void) static void setup_namespaces(struct lo_data *lo, struct fuse_session *se) { pid_t child; + char template[] = "virtiofsd-XXXXXX"; + char *tmpdir; /* * Create a new pid namespace for *child* processes. We'll have to @@ -2597,12 +2599,33 @@ static void setup_namespaces(struct lo_data *lo, struct fuse_session *se) exit(1); } + tmpdir = mkdtemp(template); + if (!tmpdir) { + fuse_log(FUSE_LOG_ERR, "tmpdir(%s): %m\n", template); + exit(1); + } + + if (mount("/proc/self/fd", tmpdir, NULL, MS_BIND, NULL) < 0) { + fuse_log(FUSE_LOG_ERR, "mount(/proc/self/fd, %s, MS_BIND): %m\n", + tmpdir); + exit(1); + } + /* Now we can get our /proc/self/fd directory file descriptor */ - lo->proc_self_fd = open("/proc/self/fd", O_PATH); + lo->proc_self_fd = open(tmpdir, O_PATH); if (lo->proc_self_fd == -1) { - fuse_log(FUSE_LOG_ERR, "open(/proc/self/fd, O_PATH): %m\n"); + fuse_log(FUSE_LOG_ERR, "open(%s, O_PATH): %m\n", tmpdir); exit(1); } + + if (umount2(tmpdir, MNT_DETACH) < 0) { + fuse_log(FUSE_LOG_ERR, "umount2(%s, MNT_DETACH): %m\n", tmpdir); + exit(1); + } + + if (rmdir(tmpdir) < 0) { + fuse_log(FUSE_LOG_ERR, "rmdir(%s): %m\n", tmpdir); + } } /*