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=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 C5184FA372A for ; Wed, 16 Oct 2019 16:09:28 +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 9E6D22067D for ; Wed, 16 Oct 2019 16:09:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9E6D22067D 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]:45178 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iKlrb-0001aK-Gu for qemu-devel@archiver.kernel.org; Wed, 16 Oct 2019 12:09:27 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57532) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iKlkp-0003xL-Oy for qemu-devel@nongnu.org; Wed, 16 Oct 2019 12:02:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iKlko-0008Gx-9U for qemu-devel@nongnu.org; Wed, 16 Oct 2019 12:02:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37642) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iKlko-0008GW-1g for qemu-devel@nongnu.org; Wed, 16 Oct 2019 12:02:26 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4D1F63DE04 for ; Wed, 16 Oct 2019 16:02:25 +0000 (UTC) Received: from localhost (unknown [10.36.118.69]) by smtp.corp.redhat.com (Postfix) with ESMTP id E6E5E5C1D6; Wed, 16 Oct 2019 16:02:19 +0000 (UTC) From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH 2/2] virtiofsd: move to a new pid namespace Date: Wed, 16 Oct 2019 17:01:57 +0100 Message-Id: <20191016160157.12414-3-stefanha@redhat.com> In-Reply-To: <20191016160157.12414-1-stefanha@redhat.com> References: <20191016160157.12414-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Wed, 16 Oct 2019 16:02:25 +0000 (UTC) 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: 209.132.183.28 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, "Dr. David Alan Gilbert" , Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 | 95 ++++++++++++++++++++++-------- 1 file changed, 72 insertions(+), 23 deletions(-) diff --git a/contrib/virtiofsd/passthrough_ll.c b/contrib/virtiofsd/passt= hrough_ll.c index c27ff7d800..b6ee9b2e90 100644 --- a/contrib/virtiofsd/passthrough_ll.c +++ b/contrib/virtiofsd/passthrough_ll.c @@ -56,9 +56,12 @@ #include #include #include +#include #include +#include #include =20 + #include "ireg.h" #include #include @@ -2749,6 +2752,72 @@ static void setup_net_namespace(void) } } =20 +/* + * Move to a new pid namespace to prevent access to other processes if t= his + * process is compromised. + */ +static void setup_pid_namespace(void) +{ + pid_t child; + + /* + * Create a new pid namespace for *child* processes. We'll have to + * fork in order to enter the new pid namespace. A new mount namespace + * is also needed so that we can remount /proc for the new pid + * namespace. + */ + if (unshare(CLONE_NEWPID | CLONE_NEWNS) !=3D 0) { + fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWPID | CLONE_NEWNS): %m\n"); + exit(1); + } + + child =3D fork(); + if (child < 0) { + fuse_log(FUSE_LOG_ERR, "fork() failed: %m\n"); + exit(1); + } + if (child > 0) { + pid_t waited; + int wstatus; + + /* The parent waits for the child */ + do { + waited =3D waitpid(child, &wstatus, 0); + } while (waited < 0 && errno =3D=3D EINTR); + + if (WIFEXITED(wstatus)) { + exit(WEXITSTATUS(wstatus)); + } + + exit(1); + } + + /* + * If the mounts have shared propagation then we want to opt out so our + * mount changes don't affect the parent mount namespace. + */ + if (mount(NULL, "/", NULL, MS_REC|MS_SLAVE, NULL) < 0) { + fuse_log(FUSE_LOG_ERR, "mount(/, MS_REC|MS_SLAVE): %m\n"); + exit(1); + } + + /* The child must remount /proc to use the new pid namespace */ + if (mount("proc", "/proc", "proc", + MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RELATIME, NULL) < 0) { + fuse_log(FUSE_LOG_ERR, "mount(/proc): %m\n"); + exit(1); + } +} + +static void setup_proc_self_fd(struct lo_data *lo) +{ + lo->proc_self_fd =3D open("/proc/self/fd", O_PATH); + if (lo->proc_self_fd =3D=3D -1) { + fuse_log(FUSE_LOG_ERR, "open(/proc/self/fd, O_PATH): %m\n"); + exit(1); + } +} + /* This magic is based on lxc's lxc_pivot_root() */ static void setup_pivot_root(const char *source) { @@ -2803,20 +2872,10 @@ static void setup_pivot_root(const char *source) =20 /* * Make the source directory our root so symlinks cannot escape and no o= ther - * files are accessible. + * files are accessible. Assumes unshare(CLONE_NEWNS) was already calle= d. */ static void setup_mount_namespace(const char *source) { - if (unshare(CLONE_NEWNS) !=3D 0) { - fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWNS): %m\n"); - exit(1); - } - - if (mount(NULL, "/", NULL, MS_REC|MS_SLAVE, NULL) < 0) { - fuse_log(FUSE_LOG_ERR, "mount(/, MS_REC|MS_PRIVATE): %m\n"); - exit(1); - } - if (mount(source, source, NULL, MS_BIND, NULL) < 0) { fuse_log(FUSE_LOG_ERR, "mount(%s, %s, MS_BIND): %m\n", source, source)= ; exit(1); @@ -2831,6 +2890,8 @@ static void setup_mount_namespace(const char *sourc= e) */ static void setup_sandbox(struct lo_data *lo, bool enable_syslog) { + setup_pid_namespace(); + setup_proc_self_fd(lo); setup_net_namespace(); setup_mount_namespace(lo->source); setup_seccomp(enable_syslog); @@ -2860,15 +2921,6 @@ static void setup_root(struct lo_data *lo, struct = lo_inode *root) g_atomic_int_set(&root->refcount, 2); } =20 -static void setup_proc_self_fd(struct lo_data *lo) -{ - lo->proc_self_fd =3D open("/proc/self/fd", O_PATH); - if (lo->proc_self_fd =3D=3D -1) { - fuse_log(FUSE_LOG_ERR, "open(/proc/self/fd, O_PATH): %m\n"); - exit(1); - } -} - /* Raise the maximum number of open file descriptors to the system limit= */ static void setup_nofile_rlimit(void) { @@ -3110,9 +3162,6 @@ int main(int argc, char *argv[]) get_shared(&lo, &lo.root); } =20 - /* Must be after daemonize to get the right /proc/self/fd */ - setup_proc_self_fd(&lo); - setup_sandbox(&lo, opts.syslog); =20 setup_root(&lo, &lo.root); --=20 2.21.0