From 41e91ccdf9fa3097d7b90718cc83e743f4dc8d6b Mon Sep 17 00:00:00 2001
From: Jan Rybar <jrybar@redhat.com>
Date: Thu, 17 Aug 2017 18:01:42 +0200
Subject: [PATCH] nspawn: new option to start as PID2
Cherry-picked from: 7732f92
Resolves: #1417387
---
Makefile.am | 2 +
man/systemd-nspawn.xml | 65 +++++++++--
src/nspawn/nspawn-stub-pid1.c | 196 ++++++++++++++++++++++++++++++++++
src/nspawn/nspawn-stub-pid1.h | 22 ++++
src/nspawn/nspawn.c | 56 ++++++++--
5 files changed, 328 insertions(+), 13 deletions(-)
create mode 100644 src/nspawn/nspawn-stub-pid1.c
create mode 100644 src/nspawn/nspawn-stub-pid1.h
diff --git a/Makefile.am b/Makefile.am
index 7c58fd0504..0e2f8d561c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2658,6 +2658,8 @@ systemd_cgtop_LDADD = \
# ------------------------------------------------------------------------------
systemd_nspawn_SOURCES = \
src/nspawn/nspawn.c \
+ src/nspawn/nspawn-stub-pid1.c \
+ src/nspawn/nspawn-stub-pid1.h \
src/core/mount-setup.c \
src/core/mount-setup.h \
src/core/loopback-setup.c \
diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index cbd44d4aba..d0eddaacc3 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -241,16 +241,69 @@
<option>--ephemeral</option>.</para></listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>-a</option></term>
+ <term><option>--as-pid2</option></term>
+
+ <listitem><para>Invoke the shell or specified program as process ID (PID) 2 instead of PID 1 (init). By
+ default, if neither this option nor <option>--boot</option> is used, the selected binary is run as process with
+ PID 1, a mode only suitable for programs that are aware of the special semantics that the process with PID 1
+ has on UNIX. For example, it needs to reap all processes reparented to it, and should implement
+ <command>sysvinit</command> compatible signal handling (specifically: it needs to reboot on SIGINT, reexecute
+ on SIGTERM, reload configuration on SIGHUP, and so on). With <option>--as-pid2</option> a minimal stub init
+ process is run as PID 1 and the selected binary is executed as PID 2 (and hence does not need to implement any
+ special semantics). The stub init process will reap processes as necessary and react appropriately to
+ signals. It is recommended to use this mode to invoke arbitrary commands in containers, unless they have been
+ modified to run correctly as PID 1. Or in other words: this switch should be used for pretty much all commands,
+ except when the command refers to an init or shell implementation, as these are generally capable of running
+ correctly as PID 1). This option may not be combined with <option>--boot</option> or
+ <option>--share-system</option>.</para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><option>-b</option></term>
<term><option>--boot</option></term>
- <listitem><para>Automatically search for an init binary and
- invoke it instead of a shell or a user supplied program. If
- this option is used, arguments specified on the command line
- are used as arguments for the init binary. This option may not
- be combined with <option>--share-system</option>.
- </para></listitem>
+ <listitem><para>Automatically search for an init binary and invoke it as PID 1, instead of a shell or a user
+ supplied program. If this option is used, arguments specified on the command line are used as arguments for the
+ init binary. This option may not be combined with <option>--as-pid2</option> or
+ <option>--share-system</option>.</para>
+
+ <para>The following table explains the different modes of invocation and relationship to
+ <option>--as-pid2</option> (see above):</para>
+
+ <table>
+ <title>Invocation Mode</title>
+ <tgroup cols='2' align='left' colsep='1' rowsep='1'>
+ <colspec colname="switch" />
+ <colspec colname="explanation" />
+ <thead>
+ <row>
+ <entry>Switch</entry>
+ <entry>Explanation</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>Neither <option>--as-pid2</option> nor <option>--boot</option> specified</entry>
+ <entry>The passed parameters are interpreted as command line, which is executed as PID 1 in the container.</entry>
+ </row>
+
+ <row>
+ <entry><option>--as-pid2</option> specified</entry>
+ <entry>The passed parameters are interpreted as command line, which are executed as PID 2 in the container. A stub init process is run as PID 1.</entry>
+ </row>
+
+ <row>
+ <entry><option>--boot</option> specified</entry>
+ <entry>An init binary as automatically searched and run as PID 1 in the container. The passed parameters are used as invocation parameters for this process.</entry>
+ </row>
+
+ </tbody>
+ </tgroup>
+ </table>
+ </listitem>
</varlistentry>
<varlistentry>
diff --git a/src/nspawn/nspawn-stub-pid1.c b/src/nspawn/nspawn-stub-pid1.c
new file mode 100644
index 0000000000..11c11560c4
--- /dev/null
+++ b/src/nspawn/nspawn-stub-pid1.c
@@ -0,0 +1,196 @@
+/***
+ This file is part of systemd.
+
+ Copyright 2016 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <sys/reboot.h>
+#include <sys/unistd.h>
+#include <sys/wait.h>
+#include <sys/prctl.h>
+
+#include "log.h"
+#include "nspawn-stub-pid1.h"
+#include "util.h"
+#include "time-util.h"
+#include "def.h"
+
+static int reset_environ(const char *new_environment, size_t length) {
+ unsigned long start, end;
+
+ start = (unsigned long) new_environment;
+ end = start + length;
+
+ if (prctl(PR_SET_MM, PR_SET_MM_ENV_START, start, 0, 0) < 0)
+ return -errno;
+
+ if (prctl(PR_SET_MM, PR_SET_MM_ENV_END, end, 0, 0) < 0)
+ return -errno;
+
+ return 0;
+}
+
+int stub_pid1(sd_id128_t uuid) {
+ enum {
+ STATE_RUNNING,
+ STATE_REBOOT,
+ STATE_POWEROFF,
+ } state = STATE_RUNNING;
+
+ sigset_t fullmask, oldmask, waitmask;
+ usec_t quit_usec = USEC_INFINITY;
+ pid_t pid;
+ int r;
+
+ /* The new environment we set up, on the stack. */
+ char new_environment[] =
+ "container=systemd-nspawn\0"
+ "container_uuid=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
+
+ /* Implements a stub PID 1, that reaps all processes and processes a couple of standard signals. This is useful
+ * for allowing arbitrary processes run in a container, and still have all zombies reaped. */
+
+ assert_se(sigfillset(&fullmask) >= 0);
+ assert_se(sigprocmask(SIG_BLOCK, &fullmask, &oldmask) >= 0);
+
+ pid = fork();
+ if (pid < 0)
+ return log_error_errno(errno, "Failed to fork child pid: %m");
+
+ if (pid == 0) {
+ /* Return in the child */
+ assert_se(sigprocmask(SIG_SETMASK, &oldmask, NULL) >= 0);
+ setsid();
+ return 0;
+ }
+
+ reset_all_signal_handlers();
+
+ log_close();
+ close_all_fds(NULL, 0);
+ log_open();
+
+ /* Flush out /proc/self/environ, so that we don't leak the environment from the host into the container. Also,
+ * set $container= and $container_uuid= so that clients in the container that query it from /proc/1/environ
+ * find them set. */
+ sd_id128_to_string(uuid, new_environment + sizeof(new_environment) - SD_ID128_STRING_MAX);
+ reset_environ(new_environment, sizeof(new_environment));
+
+ rename_process("STUBINIT");
+
+ assert_se(sigemptyset(&waitmask) >= 0);
+
+ sigset_add_many(&waitmask,
+ SIGCHLD, /* posix: process died */
+ SIGINT, /* sysv: ctrl-alt-del */
+ SIGRTMIN+3, /* systemd: halt */
+ SIGRTMIN+4, /* systemd: poweroff */
+ SIGRTMIN+5, /* systemd: reboot */
+ SIGRTMIN+6, /* systemd: kexec */
+ SIGRTMIN+13, /* systemd: halt */
+ SIGRTMIN+14, /* systemd: poweroff */
+ SIGRTMIN+15, /* systemd: reboot */
+ SIGRTMIN+16, /* systemd: kexec */
+ -1);
+
+ /* Note that we ignore SIGTERM (sysv's reexec), SIGHUP (reload), and all other signals here, since we don't
+ * support reexec/reloading in this stub process. */
+
+ for (;;) {
+ siginfo_t si;
+ usec_t current_usec;
+
+ si.si_pid = 0;
+ r = waitid(P_ALL, 0, &si, WEXITED|WNOHANG);
+ if (r < 0) {
+ r = log_error_errno(errno, "Failed to reap children: %m");
+ goto finish;
+ }
+
+ current_usec = now(CLOCK_MONOTONIC);
+
+ if (si.si_pid == pid || current_usec >= quit_usec) {
+
+ /* The child we started ourselves died or we reached a timeout. */
+
+ if (state == STATE_REBOOT) { /* dispatch a queued reboot */
+ (void) reboot(RB_AUTOBOOT);
+ r = log_error_errno(errno, "Failed to reboot: %m");
+ goto finish;
+
+ } else if (state == STATE_POWEROFF)
+ (void) reboot(RB_POWER_OFF); /* if this fails, fall back to normal exit. */
+
+ if (si.si_pid == pid && si.si_code == CLD_EXITED)
+ r = si.si_status; /* pass on exit code */
+ else
+ r = 255; /* signal, coredump, timeout, … */
+
+ goto finish;
+ }
+ if (si.si_pid != 0)
+ /* We reaped something. Retry until there's nothing more to reap. */
+ continue;
+
+ if (quit_usec == USEC_INFINITY)
+ r = sigwaitinfo(&waitmask, &si);
+ else {
+ struct timespec ts;
+ r = sigtimedwait(&waitmask, &si, timespec_store(&ts, quit_usec - current_usec));
+ }
+ if (r < 0) {
+ if (errno == EINTR) /* strace -p attach can result in EINTR, let's handle this nicely. */
+ continue;
+ if (errno == EAGAIN) /* timeout reached */
+ continue;
+
+ r = log_error_errno(errno, "Failed to wait for signal: %m");
+ goto finish;
+ }
+
+ if (si.si_signo == SIGCHLD)
+ continue; /* Let's reap this */
+
+ if (state != STATE_RUNNING)
+ continue;
+
+ /* Would love to use a switch() statement here, but SIGRTMIN is actually a function call, not a
+ * constant… */
+
+ if (si.si_signo == SIGRTMIN+3 ||
+ si.si_signo == SIGRTMIN+4 ||
+ si.si_signo == SIGRTMIN+13 ||
+ si.si_signo == SIGRTMIN+14)
+
+ state = STATE_POWEROFF;
+
+ else if (si.si_signo == SIGINT ||
+ si.si_signo == SIGRTMIN+5 ||
+ si.si_signo == SIGRTMIN+6 ||
+ si.si_signo == SIGRTMIN+15 ||
+ si.si_signo == SIGRTMIN+16)
+
+ state = STATE_REBOOT;
+ else
+ assert_not_reached("Got unexpected signal");
+
+ /* (void) kill_and_sigcont(pid, SIGTERM); */
+ quit_usec = now(CLOCK_MONOTONIC) + DEFAULT_TIMEOUT_USEC;
+ }
+
+finish:
+ _exit(r < 0 ? EXIT_FAILURE : r);
+}
diff --git a/src/nspawn/nspawn-stub-pid1.h b/src/nspawn/nspawn-stub-pid1.h
new file mode 100644
index 0000000000..be0f1af4cb
--- /dev/null
+++ b/src/nspawn/nspawn-stub-pid1.h
@@ -0,0 +1,22 @@
+#pragma once
+
+/***
+ This file is part of systemd.
+
+ Copyright 2016 Lennart Poettering
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+int stub_pid1(sd_id128_t uuid);
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index d0003d3790..ea365b3f9b 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -99,6 +99,7 @@
#include "in-addr-util.h"
#include "fw-util.h"
#include "local-addresses.h"
+#include "nspawn-stub-pid1.h"
#ifdef HAVE_SECCOMP
#include "seccomp-util.h"
@@ -129,6 +130,14 @@ typedef enum Volatile {
VOLATILE_STATE,
} Volatile;
+typedef enum StartMode {
+ START_PID1, /* Run parameters as command line as process 1 */
+ START_PID2, /* Use stub init process as PID 1, run parameters as command line as process 2 */
+ START_BOOT, /* Search for init system, pass arguments as parameters */
+ _START_MODE_MAX,
+ _START_MODE_INVALID = -1
+} StartMode;
+
static char *arg_directory = NULL;
static char *arg_template = NULL;
static char *arg_user = NULL;
@@ -139,7 +148,7 @@ static const char *arg_selinux_apifs_context = NULL;
static const char *arg_slice = NULL;
static bool arg_private_network = false;
static bool arg_read_only = false;
-static bool arg_boot = false;
+static StartMode arg_start_mode = START_PID1;
static bool arg_ephemeral = false;
static LinkJournal arg_link_journal = LINK_AUTO;
static bool arg_link_journal_try = false;
@@ -200,6 +209,7 @@ static void help(void) {
" -x --ephemeral Run container with snapshot of root directory, and\n"
" remove it after exit\n"
" -i --image=PATH File system device or disk image for the container\n"
+ " -a --as-pid2 Maintain a stub init as PID1, invoke binary as PID2\n"
" -b --boot Boot up full system (i.e. invoke init)\n"
" -u --user=USER Run the command under specified user or uid\n"
" -M --machine=NAME Set the machine name for the container\n"
@@ -304,6 +314,7 @@ static int parse_argv(int argc, char *argv[]) {
{ "ephemeral", no_argument, NULL, 'x' },
{ "user", required_argument, NULL, 'u' },
{ "private-network", no_argument, NULL, ARG_PRIVATE_NETWORK },
+ { "as-pid2", no_argument, NULL, 'a' },
{ "boot", no_argument, NULL, 'b' },
{ "uuid", required_argument, NULL, ARG_UUID },
{ "read-only", no_argument, NULL, ARG_READ_ONLY },
@@ -340,7 +351,7 @@ static int parse_argv(int argc, char *argv[]) {
assert(argc >= 0);
assert(argv);
- while ((c = getopt_long(argc, argv, "+hD:u:bL:M:jS:Z:qi:xp:n", options, NULL)) >= 0)
+ while ((c = getopt_long(argc, argv, "+hD:u:abL:M:jS:Z:qi:xp:n", options, NULL)) >= 0)
switch (c) {
@@ -421,7 +432,21 @@ static int parse_argv(int argc, char *argv[]) {
break;
case 'b':
- arg_boot = true;
+ if (arg_start_mode == START_PID2) {
+ log_error("--boot and --as-pid2 may not be combined.");
+ return -EINVAL;
+ }
+
+ arg_start_mode = START_BOOT;
+ break;
+
+ case 'a':
+ if (arg_start_mode == START_BOOT) {
+ log_error("--boot and --as-pid2 may not be combined.");
+ return -EINVAL;
+ }
+
+ arg_start_mode = START_PID2;
break;
case ARG_UUID:
@@ -741,7 +766,7 @@ static int parse_argv(int argc, char *argv[]) {
if (arg_share_system)
arg_register = false;
- if (arg_boot && arg_share_system) {
+ if (arg_start_mode != START_PID1 && arg_share_system) {
log_error("--boot and --share-system may not be combined.");
return -EINVAL;
}
@@ -3586,6 +3611,10 @@ int main(int argc, char *argv[]) {
log_parse_environment();
log_open();
+ /* Make sure rename_process() in the stub init process can work */
+ saved_argv = argv;
+ saved_argc = argc;
+
r = parse_argv(argc, argv);
if (r <= 0)
goto finish;
@@ -3694,7 +3723,7 @@ int main(int argc, char *argv[]) {
}
}
- if (arg_boot) {
+ if (arg_start_mode == START_BOOT) {
if (path_is_os_tree(arg_directory) <= 0) {
log_error("Directory %s doesn't look like an OS root directory (os-release file is missing). Refusing.", arg_directory);
r = -EINVAL;
@@ -4109,7 +4138,19 @@ int main(int argc, char *argv[]) {
if (!barrier_place_and_sync(&barrier))
_exit(EXIT_FAILURE);
- if (arg_boot) {
+ if (arg_start_mode == START_PID2) {
+ r = stub_pid1(arg_uuid);
+ if (r < 0)
+ {
+ log_error_errno(r, "Failed to start as PID2: %m");
+ _exit(EXIT_FAILURE);
+ }
+ }
+
+ log_close();
+ (void) fdset_close_others(fds);
+
+ if (arg_start_mode == START_BOOT) {
char **a;
size_t l;
@@ -4135,6 +4176,7 @@ int main(int argc, char *argv[]) {
execle("/bin/sh", "-sh", NULL, env_use);
}
+ log_open();
log_error_errno(errno, "execv() failed: %m");
_exit(EXIT_FAILURE);
}
@@ -4210,7 +4252,7 @@ int main(int argc, char *argv[]) {
goto finish;
}
- if (arg_boot) {
+ if (arg_start_mode == START_BOOT) {
/* Try to kill the init system on SIGINT or SIGTERM */
sd_event_add_signal(event, NULL, SIGINT, on_orderly_shutdown, UINT32_TO_PTR(pid));
sd_event_add_signal(event, NULL, SIGTERM, on_orderly_shutdown, UINT32_TO_PTR(pid));
