417116f234
ReadOnlySystem= uses fs namespaces to mount /usr and /boot read-only for a service. ProtectedHome= uses fs namespaces to mount /home and /run/user inaccessible or read-only for a service. This patch also enables these settings for all our long-running services. Together they should be good building block for a minimal service sandbox, removing the ability for services to modify the operating system or access the user's private data.
608 lines
16 KiB
C
608 lines
16 KiB
C
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <sys/mount.h>
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#include <string.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sched.h>
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#include <sys/syscall.h>
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#include <limits.h>
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#include <linux/fs.h>
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#include <sys/file.h>
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#include "strv.h"
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#include "util.h"
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#include "path-util.h"
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#include "namespace.h"
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#include "missing.h"
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#include "execute.h"
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#include "loopback-setup.h"
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#include "mkdir.h"
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#include "dev-setup.h"
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#include "def.h"
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typedef enum MountMode {
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/* This is ordered by priority! */
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INACCESSIBLE,
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READONLY,
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PRIVATE_TMP,
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PRIVATE_VAR_TMP,
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PRIVATE_DEV,
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READWRITE
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} MountMode;
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typedef struct BindMount {
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const char *path;
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MountMode mode;
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bool done;
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bool ignore;
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} BindMount;
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static int append_mounts(BindMount **p, char **strv, MountMode mode) {
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char **i;
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assert(p);
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STRV_FOREACH(i, strv) {
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(*p)->ignore = false;
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if ((mode == INACCESSIBLE || mode == READONLY || mode == READWRITE) && (*i)[0] == '-') {
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(*p)->ignore = true;
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(*i)++;
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}
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if (!path_is_absolute(*i))
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return -EINVAL;
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(*p)->path = *i;
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(*p)->mode = mode;
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(*p)++;
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}
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return 0;
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}
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static int mount_path_compare(const void *a, const void *b) {
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const BindMount *p = a, *q = b;
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if (path_equal(p->path, q->path)) {
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/* If the paths are equal, check the mode */
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if (p->mode < q->mode)
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return -1;
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if (p->mode > q->mode)
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return 1;
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return 0;
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}
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/* If the paths are not equal, then order prefixes first */
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if (path_startswith(p->path, q->path))
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return 1;
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if (path_startswith(q->path, p->path))
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return -1;
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return 0;
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}
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static void drop_duplicates(BindMount *m, unsigned *n) {
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BindMount *f, *t, *previous;
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assert(m);
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assert(n);
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for (f = m, t = m, previous = NULL; f < m+*n; f++) {
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/* The first one wins */
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if (previous && path_equal(f->path, previous->path))
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continue;
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t->path = f->path;
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t->mode = f->mode;
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previous = t;
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t++;
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}
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*n = t - m;
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}
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static int mount_dev(BindMount *m) {
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static const char devnodes[] =
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"/dev/null\0"
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"/dev/zero\0"
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"/dev/full\0"
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"/dev/random\0"
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"/dev/urandom\0"
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"/dev/tty\0";
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char temporary_mount[] = "/tmp/namespace-dev-XXXXXX";
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const char *d, *dev = NULL, *devpts = NULL, *devshm = NULL, *devkdbus = NULL, *devhugepages = NULL, *devmqueue = NULL;
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_cleanup_umask_ mode_t u;
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int r;
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assert(m);
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u = umask(0000);
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if (!mkdtemp(temporary_mount))
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return -errno;
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dev = strappenda(temporary_mount, "/dev");
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mkdir(dev, 0755);
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if (mount("tmpfs", dev, "tmpfs", MS_NOSUID|MS_STRICTATIME, "mode=755") < 0) {
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r = -errno;
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goto fail;
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}
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devpts = strappenda(temporary_mount, "/dev/pts");
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mkdir(devpts, 0755);
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if (mount("/dev/pts", devpts, NULL, MS_BIND, NULL) < 0) {
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r = -errno;
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goto fail;
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}
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devshm = strappenda(temporary_mount, "/dev/shm");
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mkdir(devshm, 01777);
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r = mount("/dev/shm", devshm, NULL, MS_BIND, NULL);
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if (r < 0) {
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r = -errno;
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goto fail;
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}
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devmqueue = strappenda(temporary_mount, "/dev/mqueue");
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mkdir(devmqueue, 0755);
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mount("/dev/mqueue", devmqueue, NULL, MS_BIND, NULL);
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devkdbus = strappenda(temporary_mount, "/dev/kdbus");
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mkdir(devkdbus, 0755);
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mount("/dev/kdbus", devkdbus, NULL, MS_BIND, NULL);
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devhugepages = strappenda(temporary_mount, "/dev/hugepages");
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mkdir(devhugepages, 0755);
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mount("/dev/hugepages", devhugepages, NULL, MS_BIND, NULL);
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NULSTR_FOREACH(d, devnodes) {
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_cleanup_free_ char *dn = NULL;
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struct stat st;
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r = stat(d, &st);
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if (r < 0) {
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if (errno == ENOENT)
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continue;
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r = -errno;
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goto fail;
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}
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if (!S_ISBLK(st.st_mode) &&
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!S_ISCHR(st.st_mode)) {
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r = -EINVAL;
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goto fail;
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}
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if (st.st_rdev == 0)
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continue;
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dn = strappend(temporary_mount, d);
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if (!dn) {
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r = -ENOMEM;
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goto fail;
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}
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r = mknod(dn, st.st_mode, st.st_rdev);
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if (r < 0) {
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r = -errno;
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goto fail;
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}
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}
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dev_setup(temporary_mount);
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if (mount(dev, "/dev/", NULL, MS_MOVE, NULL) < 0) {
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r = -errno;
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goto fail;
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}
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rmdir(dev);
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rmdir(temporary_mount);
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return 0;
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fail:
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if (devpts)
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umount(devpts);
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if (devshm)
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umount(devshm);
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if (devkdbus)
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umount(devkdbus);
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if (devhugepages)
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umount(devhugepages);
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if (devmqueue)
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umount(devmqueue);
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if (dev) {
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umount(dev);
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rmdir(dev);
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}
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rmdir(temporary_mount);
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return r;
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}
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static int apply_mount(
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BindMount *m,
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const char *tmp_dir,
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const char *var_tmp_dir) {
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const char *what;
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int r;
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assert(m);
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switch (m->mode) {
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case PRIVATE_DEV:
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return mount_dev(m);
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case INACCESSIBLE:
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what = "/run/systemd/inaccessible";
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break;
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case READONLY:
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case READWRITE:
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what = m->path;
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break;
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case PRIVATE_TMP:
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what = tmp_dir;
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break;
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case PRIVATE_VAR_TMP:
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what = var_tmp_dir;
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break;
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default:
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assert_not_reached("Unknown mode");
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}
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assert(what);
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r = mount(what, m->path, NULL, MS_BIND|MS_REC, NULL);
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if (r >= 0)
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log_debug("Successfully mounted %s to %s", what, m->path);
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else if (m->ignore && errno == ENOENT)
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r = 0;
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return r;
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}
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static int make_read_only(BindMount *m) {
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int r;
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assert(m);
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if (m->mode != INACCESSIBLE && m->mode != READONLY)
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return 0;
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r = mount(NULL, m->path, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY|MS_REC, NULL);
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if (r < 0 && !(m->ignore && errno == ENOENT))
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return -errno;
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return 0;
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}
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int setup_namespace(
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char** read_write_dirs,
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char** read_only_dirs,
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char** inaccessible_dirs,
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char* tmp_dir,
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char* var_tmp_dir,
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bool private_dev,
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ProtectedHome protected_home,
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bool read_only_system,
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unsigned mount_flags) {
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BindMount *m, *mounts = NULL;
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unsigned n;
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int r = 0;
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if (mount_flags == 0)
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mount_flags = MS_SHARED;
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if (unshare(CLONE_NEWNS) < 0)
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return -errno;
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n = !!tmp_dir + !!var_tmp_dir +
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strv_length(read_write_dirs) +
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strv_length(read_only_dirs) +
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strv_length(inaccessible_dirs) +
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private_dev +
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(protected_home != PROTECTED_HOME_NO ? 2 : 0) +
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(read_only_system ? 2 : 0);
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if (n > 0) {
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m = mounts = (BindMount *) alloca(n * sizeof(BindMount));
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r = append_mounts(&m, read_write_dirs, READWRITE);
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if (r < 0)
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return r;
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r = append_mounts(&m, read_only_dirs, READONLY);
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if (r < 0)
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return r;
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r = append_mounts(&m, inaccessible_dirs, INACCESSIBLE);
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if (r < 0)
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return r;
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if (tmp_dir) {
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m->path = "/tmp";
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m->mode = PRIVATE_TMP;
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m++;
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}
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if (var_tmp_dir) {
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m->path = "/var/tmp";
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m->mode = PRIVATE_VAR_TMP;
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m++;
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}
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if (private_dev) {
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m->path = "/dev";
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m->mode = PRIVATE_DEV;
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m++;
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}
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if (protected_home != PROTECTED_HOME_NO) {
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r = append_mounts(&m, STRV_MAKE("-/home", "-/run/user"), protected_home == PROTECTED_HOME_READ_ONLY ? READONLY : INACCESSIBLE);
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if (r < 0)
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return r;
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}
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if (read_only_system) {
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r = append_mounts(&m, STRV_MAKE("/usr", "-/boot"), READONLY);
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if (r < 0)
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return r;
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}
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assert(mounts + n == m);
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qsort(mounts, n, sizeof(BindMount), mount_path_compare);
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drop_duplicates(mounts, &n);
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}
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if (n > 0) {
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/* Remount / as SLAVE so that nothing now mounted in the namespace
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shows up in the parent */
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if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)
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return -errno;
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for (m = mounts; m < mounts + n; ++m) {
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r = apply_mount(m, tmp_dir, var_tmp_dir);
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if (r < 0)
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goto fail;
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}
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for (m = mounts; m < mounts + n; ++m) {
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r = make_read_only(m);
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if (r < 0)
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goto fail;
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}
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}
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/* Remount / as the desired mode. Not that this will not
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* reestablish propagation from our side to the host, since
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* what's disconnected is disconnected. */
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if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) {
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r = -errno;
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goto fail;
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}
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return 0;
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fail:
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if (n > 0) {
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for (m = mounts; m < mounts + n; ++m)
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if (m->done)
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umount2(m->path, MNT_DETACH);
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}
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return r;
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}
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static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) {
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_cleanup_free_ char *x = NULL;
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char bid[SD_ID128_STRING_MAX];
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sd_id128_t boot_id;
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int r;
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assert(id);
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assert(prefix);
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assert(path);
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/* We include the boot id in the directory so that after a
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* reboot we can easily identify obsolete directories. */
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r = sd_id128_get_boot(&boot_id);
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if (r < 0)
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return r;
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x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX", NULL);
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if (!x)
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return -ENOMEM;
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RUN_WITH_UMASK(0077)
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if (!mkdtemp(x))
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return -errno;
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RUN_WITH_UMASK(0000) {
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char *y;
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y = strappenda(x, "/tmp");
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if (mkdir(y, 0777 | S_ISVTX) < 0)
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return -errno;
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}
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*path = x;
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x = NULL;
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return 0;
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}
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int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) {
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char *a, *b;
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int r;
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assert(id);
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assert(tmp_dir);
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assert(var_tmp_dir);
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r = setup_one_tmp_dir(id, "/tmp", &a);
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if (r < 0)
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return r;
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r = setup_one_tmp_dir(id, "/var/tmp", &b);
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if (r < 0) {
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char *t;
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t = strappenda(a, "/tmp");
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rmdir(t);
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rmdir(a);
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free(a);
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return r;
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}
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*tmp_dir = a;
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*var_tmp_dir = b;
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return 0;
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}
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|
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int setup_netns(int netns_storage_socket[2]) {
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_cleanup_close_ int netns = -1;
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union {
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struct cmsghdr cmsghdr;
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uint8_t buf[CMSG_SPACE(sizeof(int))];
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} control = {};
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struct msghdr mh = {
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.msg_control = &control,
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.msg_controllen = sizeof(control),
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};
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struct cmsghdr *cmsg;
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int r;
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|
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assert(netns_storage_socket);
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assert(netns_storage_socket[0] >= 0);
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assert(netns_storage_socket[1] >= 0);
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|
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/* We use the passed socketpair as a storage buffer for our
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* namespace reference fd. Whatever process runs this first
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* shall create a new namespace, all others should just join
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* it. To serialize that we use a file lock on the socket
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|
* pair.
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|
*
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* It's a bit crazy, but hey, works great! */
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|
|
if (lockf(netns_storage_socket[0], F_LOCK, 0) < 0)
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return -errno;
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|
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if (recvmsg(netns_storage_socket[0], &mh, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) < 0) {
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|
if (errno != EAGAIN) {
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r = -errno;
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goto fail;
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}
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/* Nothing stored yet, so let's create a new namespace */
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|
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if (unshare(CLONE_NEWNET) < 0) {
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r = -errno;
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goto fail;
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}
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|
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loopback_setup();
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|
|
netns = open("/proc/self/ns/net", O_RDONLY|O_CLOEXEC|O_NOCTTY);
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|
if (netns < 0) {
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r = -errno;
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goto fail;
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}
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r = 1;
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} else {
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/* Yay, found something, so let's join the namespace */
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for (cmsg = CMSG_FIRSTHDR(&mh); cmsg; cmsg = CMSG_NXTHDR(&mh, cmsg)) {
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if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {
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assert(cmsg->cmsg_len == CMSG_LEN(sizeof(int)));
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netns = *(int*) CMSG_DATA(cmsg);
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}
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}
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if (setns(netns, CLONE_NEWNET) < 0) {
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r = -errno;
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|
goto fail;
|
|
}
|
|
|
|
r = 0;
|
|
}
|
|
|
|
cmsg = CMSG_FIRSTHDR(&mh);
|
|
cmsg->cmsg_level = SOL_SOCKET;
|
|
cmsg->cmsg_type = SCM_RIGHTS;
|
|
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
|
|
memcpy(CMSG_DATA(cmsg), &netns, sizeof(int));
|
|
mh.msg_controllen = cmsg->cmsg_len;
|
|
|
|
if (sendmsg(netns_storage_socket[1], &mh, MSG_DONTWAIT|MSG_NOSIGNAL) < 0) {
|
|
r = -errno;
|
|
goto fail;
|
|
}
|
|
|
|
fail:
|
|
lockf(netns_storage_socket[0], F_ULOCK, 0);
|
|
|
|
return r;
|
|
}
|
|
|
|
static const char *const protected_home_table[_PROTECTED_HOME_MAX] = {
|
|
[PROTECTED_HOME_NO] = "no",
|
|
[PROTECTED_HOME_YES] = "yes",
|
|
[PROTECTED_HOME_READ_ONLY] = "read-only",
|
|
};
|
|
|
|
DEFINE_STRING_TABLE_LOOKUP(protected_home, ProtectedHome);
|