From nobody Fri Oct 3 11:41:04 2025 Delivered-To: importer@patchew.org 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; Authentication-Results: mx.zohomail.com; dkim=pass; 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; dmarc=pass(p=none dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1579804040; cv=none; d=zohomail.com; s=zohoarc; b=O3SOjCU9T64BS927n+D2ov+iKH1gnL3sxqpBBQwpeuSoAX3ajJZ4IJMFRHz684F2gY6e9om4lrYREt7wmZC7DdCnHxaly++Rw0F0zJBOjS6zAgRlXOVqJ7mM5J57C0pkZ8/8OV+3Sr+iIRib+GU6AeqEc9tRKMfIzsLw47uKuqY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1579804040; h=Content-Type:Content-Transfer-Encoding:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=HcX+rlmsOnPkAnqht3vH74Z9QoTWqy14xncBYAwsD2g=; b=GkBnsV/jb4+0AqDxixPUsK8H1cPD2adIlAnPD2Kkd21Ttjdx/mWIlq1h9Hp2HaF702mSM3VvV61ahaB/HJ+NGKaapSrJkNclZuNqejetsqfiv8yImc5PdJBsMAA2JGKykP0+fsFMrWfqeBEkhx/g7LrrkVyAKGW7SrvmDPn/iAI= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; 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; dmarc=pass header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1579804040679684.3982041268878; Thu, 23 Jan 2020 10:27:20 -0800 (PST) Received: from localhost ([::1]:34698 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iuhCI-0003Gm-W3 for importer@patchew.org; Thu, 23 Jan 2020 13:27:19 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:41420) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iufe7-00058g-GE for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iufe5-0006dY-Ov for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:55 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:59254 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iufe5-0006dE-Lt for qemu-devel@nongnu.org; Thu, 23 Jan 2020 11:47:53 -0500 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-402-wnCb0o13OiGh2UFFXY9jhQ-1; Thu, 23 Jan 2020 11:47:49 -0500 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 67D971085942 for ; Thu, 23 Jan 2020 16:47:48 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-116-110.ams2.redhat.com [10.36.116.110]) by smtp.corp.redhat.com (Postfix) with ESMTP id B55B628993; Thu, 23 Jan 2020 16:47:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579798073; 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=HcX+rlmsOnPkAnqht3vH74Z9QoTWqy14xncBYAwsD2g=; b=IkOJ+U1njT8EDbOvlESZ/+8jSv7UnsSy1wUIuO7/lulUf2cCn6fDvsIowZ9ewUaxE0+GlX rxq+OPrP+mjVWQ36cymj/zkzBlXN33nL1hn5k3CbiaDfg1uN8MxbBpYLqN2NBvBbSW0VeH GBqZ/Qa5e7q1lIXHEMQT9tBLCnXm21M= From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, stefanha@redhat.com Subject: [PULL 051/108] virtiofsd: move to a new pid namespace Date: Thu, 23 Jan 2020 16:45:33 +0000 Message-Id: <20200123164630.91498-52-dgilbert@redhat.com> In-Reply-To: <20200123164630.91498-1-dgilbert@redhat.com> References: <20200123164630.91498-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: wnCb0o13OiGh2UFFXY9jhQ-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 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+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Daniel P. Berrang=C3=A9 Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/passthrough_ll.c | 134 ++++++++++++++++++++----------- 1 file changed, 86 insertions(+), 48 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough= _ll.c index 27ab328722..0947d14e5b 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -51,7 +51,10 @@ #include #include #include +#include #include +#include +#include #include #include =20 @@ -1945,24 +1948,95 @@ static void print_capabilities(void) } =20 /* - * Called after our UNIX domain sockets have been created, now we can move= to - * an empty network namespace to prevent TCP/IP and other network activity= in - * case this process is compromised. + * Move to a new mount, net, and pid namespaces to isolate this process. */ -static void setup_net_namespace(void) +static void setup_namespaces(struct lo_data *lo, struct fuse_session *se) { - if (unshare(CLONE_NEWNET) !=3D 0) { - fuse_log(FUSE_LOG_ERR, "unshare(CLONE_NEWNET): %m\n"); + 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. + * + * Our UNIX domain sockets have been created. Now we can move to + * an empty network namespace to prevent TCP/IP and other network + * activity in case this process is compromised. + */ + if (unshare(CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWNET) !=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 && !se->exited); + + /* We were terminated by a signal, see fuse_signals.c */ + if (se->exited) { + exit(0); + } + + if (WIFEXITED(wstatus)) { + exit(WEXITSTATUS(wstatus)); + } + + exit(1); + } + + /* Send us SIGTERM when the parent thread terminates, see prctl(2) */ + prctl(PR_SET_PDEATHSIG, SIGTERM); + + /* + * 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); + } + + /* Now we can get our /proc/self/fd directory file descriptor */ + 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); } } =20 -/* This magic is based on lxc's lxc_pivot_root() */ -static void setup_pivot_root(const char *source) +/* + * Make the source directory our root so symlinks cannot escape and no oth= er + * files are accessible. Assumes unshare(CLONE_NEWNS) was already called. + */ +static void setup_mounts(const char *source) { int oldroot; int newroot; =20 + if (mount(source, source, NULL, MS_BIND, NULL) < 0) { + fuse_log(FUSE_LOG_ERR, "mount(%s, %s, MS_BIND): %m\n", source, sou= rce); + exit(1); + } + + /* This magic is based on lxc's lxc_pivot_root() */ oldroot =3D open("/", O_DIRECTORY | O_RDONLY | O_CLOEXEC); if (oldroot < 0) { fuse_log(FUSE_LOG_ERR, "open(/): %m\n"); @@ -2009,47 +2083,14 @@ static void setup_pivot_root(const char *source) close(oldroot); } =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); - } -} - -/* - * Make the source directory our root so symlinks cannot escape and no oth= er - * files are accessible. - */ -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, sou= rce); - exit(1); - } - - setup_pivot_root(source); -} - /* * Lock down this process to prevent access to other processes or files ou= tside * source directory. This reduces the impact of arbitrary code execution = bugs. */ -static void setup_sandbox(struct lo_data *lo) +static void setup_sandbox(struct lo_data *lo, struct fuse_session *se) { - setup_net_namespace(); - setup_mount_namespace(lo->source); + setup_namespaces(lo, se); + setup_mounts(lo->source); } =20 int main(int argc, char *argv[]) @@ -2173,10 +2214,7 @@ int main(int argc, char *argv[]) =20 fuse_daemonize(opts.foreground); =20 - /* Must be after daemonize to get the right /proc/self/fd */ - setup_proc_self_fd(&lo); - - setup_sandbox(&lo); + setup_sandbox(&lo, se); =20 /* Block until ctrl+c or fusermount -u */ ret =3D virtio_loop(se); --=20 2.24.1