shaba/systemd
1
0
Fork 0
mirror of https://github.com/systemd/systemd.git synced 2024-11-07 01:27:11 +03:00
Code
86ec5e5e29
systemd/src/core/machine-id-setup.c
Lennart Poettering f53d86c929 machine-id-setup: explicitly fsync() the machine ID after writing 
As discussed here:

https://github.com/systemd/systemd/issues/2619#issuecomment-184670042

Explicitly syncing /etc/machine-id after writing it, is probably a good idea,
since it has a strong "commit" character and is generally a one-time thing.

Fixes #2619.
2016-04-22 16:06:20 +02:00

365 lines
12 KiB
C
Raw Blame History

/***
This file is part of systemd.
Copyright 2010 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 <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <stdio.h>
#include <string.h>
#include <sys/mount.h>
#include <unistd.h>
#include "sd-id128.h"
#include "alloc-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "fs-util.h"
#include "hexdecoct.h"
#include "io-util.h"
#include "log.h"
#include "machine-id-setup.h"
#include "macro.h"
#include "mkdir.h"
#include "mount-util.h"
#include "path-util.h"
#include "process-util.h"
#include "stat-util.h"
#include "string-util.h"
#include "umask-util.h"
#include "util.h"
#include "virt.h"
static int shorten_uuid(char destination[34], const char source[36]) {
unsigned i, j;
assert(destination);
assert(source);
/* Converts a UUID into a machine ID, by lowercasing it and
* removing dashes. Validates everything. */
for (i = 0, j = 0; i < 36 && j < 32; i++) {
int t;
t = unhexchar(source[i]);
if (t < 0)
continue;
destination[j++] = hexchar(t);
}
if (i != 36 || j != 32)
return -EINVAL;
destination[32] = '\n';
destination[33] = 0;
return 0;
}
static int read_machine_id(int fd, char id[34]) {
char id_to_validate[34];
int r;
assert(fd >= 0);
assert(id);
/* Reads a machine ID from a file, validates it, and returns
* it. The returned ID ends in a newline. */
r = loop_read_exact(fd, id_to_validate, 33, false);
if (r < 0)
return r;
if (id_to_validate[32] != '\n')
return -EINVAL;
id_to_validate[32] = 0;
if (!id128_is_valid(id_to_validate))
return -EINVAL;
memcpy(id, id_to_validate, 32);
id[32] = '\n';
id[33] = 0;
return 0;
}
static int write_machine_id(int fd, const char id[34]) {
int r;
assert(fd >= 0);
assert(id);
if (lseek(fd, 0, SEEK_SET) < 0)
return -errno;
r = loop_write(fd, id, 33, false);
if (r < 0)
return r;
if (fsync(fd) < 0)
return -errno;
return 0;
}
static int generate_machine_id(char id[34], const char *root) {
int fd, r;
unsigned char *p;
sd_id128_t buf;
char *q;
const char *dbus_machine_id;
assert(id);
dbus_machine_id = prefix_roota(root, "/var/lib/dbus/machine-id");
/* First, try reading the D-Bus machine id, unless it is a symlink */
fd = open(dbus_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
if (fd >= 0) {
r = read_machine_id(fd, id);
safe_close(fd);
if (r >= 0) {
log_info("Initializing machine ID from D-Bus machine ID.");
return 0;
}
}
if (isempty(root)) {
/* If that didn't work, see if we are running in a container,
* and a machine ID was passed in via $container_uuid the way
* libvirt/LXC does it */
if (detect_container() > 0) {
_cleanup_free_ char *e = NULL;
r = getenv_for_pid(1, "container_uuid", &e);
if (r > 0) {
r = shorten_uuid(id, e);
if (r >= 0) {
log_info("Initializing machine ID from container UUID.");
return 0;
}
}
} else if (detect_vm() == VIRTUALIZATION_KVM) {
/* If we are not running in a container, see if we are
* running in qemu/kvm and a machine ID was passed in
* via -uuid on the qemu/kvm command line */
char uuid[36];
fd = open("/sys/class/dmi/id/product_uuid", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
if (fd >= 0) {
r = loop_read_exact(fd, uuid, 36, false);
safe_close(fd);
if (r >= 0) {
r = shorten_uuid(id, uuid);
if (r >= 0) {
log_info("Initializing machine ID from KVM UUID.");
return 0;
}
}
}
}
}
/* If that didn't work, generate a random machine id */
r = sd_id128_randomize(&buf);
if (r < 0)
return log_error_errno(r, "Failed to open /dev/urandom: %m");
for (p = buf.bytes, q = id; p < buf.bytes + sizeof(buf); p++, q += 2) {
q[0] = hexchar(*p >> 4);
q[1] = hexchar(*p & 15);
}
id[32] = '\n';
id[33] = 0;
log_info("Initializing machine ID from random generator.");
return 0;
}
int machine_id_setup(const char *root, sd_id128_t machine_id) {
const char *etc_machine_id, *run_machine_id;
_cleanup_close_ int fd = -1;
bool writable = true;
char id[34]; /* 32 + \n + \0 */
int r;
etc_machine_id = prefix_roota(root, "/etc/machine-id");
run_machine_id = prefix_roota(root, "/run/machine-id");
RUN_WITH_UMASK(0000) {
/* We create this 0444, to indicate that this isn't really
* something you should ever modify. Of course, since the file
* will be owned by root it doesn't matter much, but maybe
* people look. */
mkdir_parents(etc_machine_id, 0755);
fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
if (fd < 0) {
int old_errno = errno;
fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0) {
if (old_errno == EROFS && errno == ENOENT)
log_error_errno(errno,
"System cannot boot: Missing /etc/machine-id and /etc is mounted read-only.\n"
"Booting up is supported only when:\n"
"1) /etc/machine-id exists and is populated.\n"
"2) /etc/machine-id exists and is empty.\n"
"3) /etc/machine-id is missing and /etc is writable.\n");
else
log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
return -errno;
}
writable = false;
}
}
/* A machine id argument overrides all other machined-ids */
if (!sd_id128_is_null(machine_id)) {
sd_id128_to_string(machine_id, id);
id[32] = '\n';
id[33] = 0;
} else {
if (read_machine_id(fd, id) >= 0)
return 0;
/* Hmm, so, the id currently stored is not useful, then let's
* generate one */
r = generate_machine_id(id, root);
if (r < 0)
return r;
}
if (writable)
if (write_machine_id(fd, id) >= 0)
return 0;
fd = safe_close(fd);
/* Hmm, we couldn't write it? So let's write it to
* /run/machine-id as a replacement */
RUN_WITH_UMASK(0022) {
r = write_string_file(run_machine_id, id, WRITE_STRING_FILE_CREATE);
if (r < 0) {
(void) unlink(run_machine_id);
return log_error_errno(r, "Cannot write %s: %m", run_machine_id);
}
}
/* And now, let's mount it over */
if (mount(run_machine_id, etc_machine_id, NULL, MS_BIND, NULL) < 0) {
(void) unlink_noerrno(run_machine_id);
return log_error_errno(errno, "Failed to mount %s: %m", etc_machine_id);
}
log_info("Installed transient %s file.", etc_machine_id);
/* Mark the mount read-only */
if (mount(NULL, etc_machine_id, NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, NULL) < 0)
log_warning_errno(errno, "Failed to make transient %s read-only: %m", etc_machine_id);
return 0;
}
int machine_id_commit(const char *root) {
_cleanup_close_ int fd = -1, initial_mntns_fd = -1;
const char *etc_machine_id;
char id[34]; /* 32 + \n + \0 */
int r;
etc_machine_id = prefix_roota(root, "/etc/machine-id");
r = path_is_mount_point(etc_machine_id, 0);
if (r < 0)
return log_error_errno(r, "Failed to determine whether %s is a mount point: %m", etc_machine_id);
if (r == 0) {
log_debug("%s is is not a mount point. Nothing to do.", etc_machine_id);
return 0;
}
/* Read existing machine-id */
fd = open(etc_machine_id, O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (fd < 0)
return log_error_errno(errno, "Cannot open %s: %m", etc_machine_id);
r = read_machine_id(fd, id);
if (r < 0)
return log_error_errno(r, "We didn't find a valid machine ID in %s.", etc_machine_id);
r = fd_is_temporary_fs(fd);
if (r < 0)
return log_error_errno(r, "Failed to determine whether %s is on a temporary file system: %m", etc_machine_id);
if (r == 0) {
log_error("%s is not on a temporary file system.", etc_machine_id);
return -EROFS;
}
fd = safe_close(fd);
/* Store current mount namespace */
r = namespace_open(0, NULL, &initial_mntns_fd, NULL, NULL, NULL);
if (r < 0)
return log_error_errno(r, "Can't fetch current mount namespace: %m");
/* Switch to a new mount namespace, isolate ourself and unmount etc_machine_id in our new namespace */
if (unshare(CLONE_NEWNS) < 0)
return log_error_errno(errno, "Failed to enter new namespace: %m");
if (mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL) < 0)
return log_error_errno(errno, "Couldn't make-rslave / mountpoint in our private namespace: %m");
if (umount(etc_machine_id) < 0)
return log_error_errno(errno, "Failed to unmount transient %s file in our private namespace: %m", etc_machine_id);
/* Update a persistent version of etc_machine_id */
fd = open(etc_machine_id, O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0444);
if (fd < 0)
return log_error_errno(errno, "Cannot open for writing %s. This is mandatory to get a persistent machine-id: %m", etc_machine_id);
r = write_machine_id(fd, id);
if (r < 0)
return log_error_errno(r, "Cannot write %s: %m", etc_machine_id);
fd = safe_close(fd);
/* Return to initial namespace and proceed a lazy tmpfs unmount */
r = namespace_enter(-1, initial_mntns_fd, -1, -1, -1);
if (r < 0)
return log_warning_errno(r, "Failed to switch back to initial mount namespace: %m.\nWe'll keep transient %s file until next reboot.", etc_machine_id);
if (umount2(etc_machine_id, MNT_DETACH) < 0)
return log_warning_errno(errno, "Failed to unmount transient %s file: %m.\nWe keep that mount until next reboot.", etc_machine_id);
return 0;
}
View Git Blame Copy Permalink