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=-6.8 required=3.0 tests=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 0F852CA9EAF for ; Thu, 24 Oct 2019 12:27:29 +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 CE29320650 for ; Thu, 24 Oct 2019 12:27:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HX5vQRmS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE29320650 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]:41026 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iNcD9-0003Oc-Id for qemu-devel@archiver.kernel.org; Thu, 24 Oct 2019 08:27:27 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:39457) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iNbII-0003wH-Pc for qemu-devel@nongnu.org; Thu, 24 Oct 2019 07:28:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iNbIH-00008K-Au for qemu-devel@nongnu.org; Thu, 24 Oct 2019 07:28:42 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:46758 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iNbIH-00008D-6c for qemu-devel@nongnu.org; Thu, 24 Oct 2019 07:28:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571916520; 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=DLd7Tp/kvk7CtQEiJaNPsk+MgWDyOqf5yg0pdVj2peM=; b=HX5vQRmSmmi4XN22FdYRbOQI9xJauVn+Xb+a7P0e0E3ETHxnM5/IOpX5xubeXbEt9QupRM YUyz8pwfkH2J1RU4TJtJgeg/1kuvqjfDh5r6d1uieaMGLSsrz/RsVxgJjkyzuqdbuVrrO7 qFwbK8NMSwEoKHGQ2NOAGPGshdqWGvs= 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-188-ADKqlAH8Mw6L7dXLM_TJBQ-1; Thu, 24 Oct 2019 07:28:37 -0400 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 A57C1800D49; Thu, 24 Oct 2019 11:28:35 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-117-248.ams2.redhat.com [10.36.117.248]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2AE3652D5; Thu, 24 Oct 2019 11:28:33 +0000 (UTC) From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, renzhen@linux.alibaba.com, eguan@linux.alibaba.com, ganesh.mahalingam@intel.com, m.mizuma@jp.fujitsu.com, mszeredi@redhat.com, misono.tomohiro@jp.fujitsu.com, tao.peng@linux.alibaba.com, piaojun@huawei.com, stefanha@redhat.com, vgoyal@redhat.com, mst@redhat.com, berrange@redhat.com Subject: [PATCH 18/25] virtiofsd: move to a new pid namespace Date: Thu, 24 Oct 2019 12:27:11 +0100 Message-Id: <20191024112718.34657-19-dgilbert@redhat.com> In-Reply-To: <20191024112718.34657-1-dgilbert@redhat.com> References: <20191024112718.34657-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: ADKqlAH8Mw6L7dXLM_TJBQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] 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: Stefan Hajnoczi virtiofsd needs access to /proc/self/fd. Let's move to a new pid namespace so that a compromised process cannot see another other processes running on the system. One wrinkle in this approach: unshare(CLONE_NEWPID) affects *child* processes and not the current process. Therefore we need to fork the pid 1 process that will actually run virtiofsd and leave a parent in waitpid(2). This is not the same thing as daemonization and parent processes should not notice a difference. Signed-off-by: Stefan Hajnoczi --- contrib/virtiofsd/passthrough_ll.c | 76 ++++++++++++++++++++++++------ 1 file changed, 62 insertions(+), 14 deletions(-) diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passthr= ough_ll.c index 58cf82a89f..c027db64e6 100644 --- a/contrib/virtiofsd/passthrough_ll.c +++ b/contrib/virtiofsd/passthrough_ll.c @@ -52,6 +52,8 @@ #include #include #include +#include +#include =20 #include "passthrough_helpers.h" =20 @@ -1835,6 +1837,63 @@ static void setup_net_namespace(void) =09} } =20 +/* + * Move to a new pid namespace to prevent access to other processes if thi= s + * process is compromised. + */ +static void setup_pid_namespace(void) +{ +=09pid_t child; + +=09/* +=09 * Create a new pid namespace for *child* processes. We'll have to +=09 * fork in order to enter the new pid namespace. A new mount namespace +=09 * is also needed so that we can remount /proc for the new pid +=09 * namespace. +=09 */ +=09if (unshare(CLONE_NEWPID | CLONE_NEWNS) !=3D 0) { +=09=09fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWPID | CLONE_NEWNS): %m\n"); +=09=09exit(1); +=09} + +=09child =3D fork(); +=09if (child < 0) { +=09=09fuse_log(FUSE_LOG_ERR, "fork() failed: %m\n"); +=09=09exit(1); +=09} +=09if (child > 0) { +=09=09pid_t waited; +=09=09int wstatus; + +=09=09/* The parent waits for the child */ +=09=09do { +=09=09=09waited =3D waitpid(child, &wstatus, 0); +=09=09} while (waited < 0 && errno =3D=3D EINTR); + +=09=09if (WIFEXITED(wstatus)) { +=09=09=09exit(WEXITSTATUS(wstatus)); +=09=09} + +=09=09exit(1); +=09} + +=09/* +=09 * If the mounts have shared propagation then we want to opt out so our +=09 * mount changes don't affect the parent mount namespace. +=09 */ +=09if (mount(NULL, "/", NULL, MS_REC|MS_SLAVE, NULL) < 0) { +=09=09fuse_log(FUSE_LOG_ERR, "mount(/, MS_REC|MS_SLAVE): %m\n"); +=09=09exit(1); +=09} + +=09/* The child must remount /proc to use the new pid namespace */ +=09if (mount("proc", "/proc", "proc", +=09=09 MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) { +=09=09fuse_log(FUSE_LOG_ERR, "mount(/proc): %m\n"); +=09=09exit(1); +=09} +} + /* This magic is based on lxc's lxc_pivot_root() */ static void setup_pivot_root(const char *source) { @@ -1898,20 +1957,10 @@ static void setup_proc_self_fd(struct lo_data *lo) =20 /* * Make the source directory our root so symlinks cannot escape and no oth= er - * files are accessible. + * files are accessible. Assumes unshare(CLONE_NEWNS) was already called. */ static void setup_mount_namespace(const char *source) { -=09if (unshare(CLONE_NEWNS) !=3D 0) { -=09=09fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWNS): %m\n"); -=09=09exit(1); -=09} - -=09if (mount(NULL, "/", NULL, MS_REC|MS_SLAVE, NULL) < 0) { -=09=09fuse_log(FUSE_LOG_ERR, "mount(/, MS_REC|MS_PRIVATE): %m\n"); -=09=09exit(1); -=09} - =09if (mount(source, source, NULL, MS_BIND, NULL) < 0) { =09=09fuse_log(FUSE_LOG_ERR, "mount(%s, %s, MS_BIND): %m\n", source, sourc= e); =09=09exit(1); @@ -1926,6 +1975,8 @@ static void setup_mount_namespace(const char *source) */ static void setup_sandbox(struct lo_data *lo) { +=09setup_pid_namespace(); +=09setup_proc_self_fd(lo); =09setup_net_namespace(); =09setup_mount_namespace(lo->source); } @@ -2046,9 +2097,6 @@ int main(int argc, char *argv[]) =20 =09fuse_daemonize(opts.foreground); =20 -=09/* Must be after daemonize to get the right /proc/self/fd */ -=09setup_proc_self_fd(&lo); - =09setup_sandbox(&lo); =20 =09/* Block until ctrl+c or fusermount -u */ --=20 2.23.0