/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ /*** 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 <sys/mount.h> #include <string.h> #include <stdio.h> #include <unistd.h> #include <sys/stat.h> #include <sys/types.h> #include <sched.h> #include <sys/syscall.h> #include <limits.h> #include <linux/fs.h> #include <sys/file.h> #include "strv.h" #include "util.h" #include "path-util.h" #include "namespace.h" #include "missing.h" #include "execute.h" #include "loopback-setup.h" #include "mkdir.h" #include "dev-setup.h" #include "def.h" typedef enum MountMode { /* This is ordered by priority! */ INACCESSIBLE, READONLY, PRIVATE_TMP, PRIVATE_VAR_TMP, PRIVATE_DEV, READWRITE } MountMode; typedef struct BindMount { const char *path; MountMode mode; bool done; bool ignore; } BindMount; static int append_mounts(BindMount **p, char **strv, MountMode mode) { char **i; assert(p); STRV_FOREACH(i, strv) { (*p)->ignore = false; if ((mode == INACCESSIBLE || mode == READONLY) && (*i)[0] == '-') { (*p)->ignore = true; (*i)++; } if (!path_is_absolute(*i)) return -EINVAL; (*p)->path = *i; (*p)->mode = mode; (*p)++; } return 0; } static int mount_path_compare(const void *a, const void *b) { const BindMount *p = a, *q = b; if (path_equal(p->path, q->path)) { /* If the paths are equal, check the mode */ if (p->mode < q->mode) return -1; if (p->mode > q->mode) return 1; return 0; } /* If the paths are not equal, then order prefixes first */ if (path_startswith(p->path, q->path)) return 1; if (path_startswith(q->path, p->path)) return -1; return 0; } static void drop_duplicates(BindMount *m, unsigned *n) { BindMount *f, *t, *previous; assert(m); assert(n); for (f = m, t = m, previous = NULL; f < m+*n; f++) { /* The first one wins */ if (previous && path_equal(f->path, previous->path)) continue; t->path = f->path; t->mode = f->mode; previous = t; t++; } *n = t - m; } static int mount_dev(BindMount *m) { static const char devnodes[] = "/dev/null\0" "/dev/zero\0" "/dev/full\0" "/dev/random\0" "/dev/urandom\0" "/dev/tty\0"; struct stat devnodes_stat[6] = {}; const char *d; unsigned n = 0; _cleanup_umask_ mode_t u; int r; assert(m); u = umask(0000); /* First: record device mode_t and dev_t */ NULSTR_FOREACH(d, devnodes) { r = stat(d, &devnodes_stat[n]); if (r < 0) { if (errno != ENOENT) return -errno; } else { if (!S_ISBLK(devnodes_stat[n].st_mode) && !S_ISCHR(devnodes_stat[n].st_mode)) return -EINVAL; } n++; } assert(n == ELEMENTSOF(devnodes_stat)); r = mount("tmpfs", "/dev", "tmpfs", MS_NOSUID|MS_STRICTATIME, "mode=755"); if (r < 0) return m->ignore ? 0 : -errno; mkdir_p("/dev/pts", 0755); r = mount("devpts", "/dev/pts", "devpts", MS_NOSUID|MS_NOEXEC, "newinstance,ptmxmode=0666,mode=620,gid=" STRINGIFY(TTY_GID)); if (r < 0) return m->ignore ? 0 : -errno; mkdir_p("/dev/shm", 0755); r = mount("tmpfs", "/dev/shm", "tmpfs", MS_NOSUID|MS_NODEV|MS_STRICTATIME, "mode=1777"); if (r < 0) return m->ignore ? 0 : -errno; /* Second: actually create it */ n = 0; NULSTR_FOREACH(d, devnodes) { if (devnodes_stat[n].st_rdev == 0) continue; r = mknod(d, devnodes_stat[n].st_mode, devnodes_stat[n].st_rdev); if (r < 0) return m->ignore ? 0 : -errno; n++; } dev_setup(NULL); return 0; } static int apply_mount( BindMount *m, const char *tmp_dir, const char *var_tmp_dir) { const char *what; int r; assert(m); switch (m->mode) { case PRIVATE_DEV: return mount_dev(m); case INACCESSIBLE: what = "/run/systemd/inaccessible"; break; case READONLY: case READWRITE: what = m->path; break; case PRIVATE_TMP: what = tmp_dir; break; case PRIVATE_VAR_TMP: what = var_tmp_dir; break; default: assert_not_reached("Unknown mode"); } assert(what); r = mount(what, m->path, NULL, MS_BIND|MS_REC, NULL); if (r >= 0) log_debug("Successfully mounted %s to %s", what, m->path); else if (m->ignore && errno == ENOENT) r = 0; return r; } static int make_read_only(BindMount *m) { int r; assert(m); if (m->mode != INACCESSIBLE && m->mode != READONLY) return 0; r = mount(NULL, m->path, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY|MS_REC, NULL); if (r < 0 && !(m->ignore && errno == ENOENT)) return -errno; return 0; } int setup_namespace( char** read_write_dirs, char** read_only_dirs, char** inaccessible_dirs, char* tmp_dir, char* var_tmp_dir, bool private_dev, unsigned mount_flags) { BindMount *m, *mounts = NULL; unsigned n; int r = 0; if (mount_flags == 0) mount_flags = MS_SHARED; if (unshare(CLONE_NEWNS) < 0) return -errno; n = !!tmp_dir + !!var_tmp_dir + strv_length(read_write_dirs) + strv_length(read_only_dirs) + strv_length(inaccessible_dirs) + private_dev; if (n > 0) { m = mounts = (BindMount *) alloca(n * sizeof(BindMount)); r = append_mounts(&m, read_write_dirs, READWRITE); if (r < 0) return r; r = append_mounts(&m, read_only_dirs, READONLY); if (r < 0) return r; r = append_mounts(&m, inaccessible_dirs, INACCESSIBLE); if (r < 0) return r; if (tmp_dir) { m->path = "/tmp"; m->mode = PRIVATE_TMP; m++; } if (var_tmp_dir) { m->path = "/var/tmp"; m->mode = PRIVATE_VAR_TMP; m++; } if (private_dev) { m->path = "/dev"; m->mode = PRIVATE_DEV; m++; } assert(mounts + n == m); qsort(mounts, n, sizeof(BindMount), mount_path_compare); drop_duplicates(mounts, &n); } /* Remount / as SLAVE so that nothing now mounted in the namespace shows up in the parent */ if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) return -errno; for (m = mounts; m < mounts + n; ++m) { r = apply_mount(m, tmp_dir, var_tmp_dir); if (r < 0) goto fail; } for (m = mounts; m < mounts + n; ++m) { r = make_read_only(m); if (r < 0) goto fail; } /* Remount / as the desired mode */ if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) { r = -errno; goto fail; } return 0; fail: for (m = mounts; m < mounts + n; ++m) if (m->done) umount2(m->path, MNT_DETACH); return r; } static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) { _cleanup_free_ char *x = NULL; char bid[SD_ID128_STRING_MAX]; sd_id128_t boot_id; int r; assert(id); assert(prefix); assert(path); /* We include the boot id in the directory so that after a * reboot we can easily identify obsolete directories. */ r = sd_id128_get_boot(&boot_id); if (r < 0) return r; x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX", NULL); if (!x) return -ENOMEM; RUN_WITH_UMASK(0077) if (!mkdtemp(x)) return -errno; RUN_WITH_UMASK(0000) { char *y; y = strappenda(x, "/tmp"); if (mkdir(y, 0777 | S_ISVTX) < 0) return -errno; } *path = x; x = NULL; return 0; } int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) { char *a, *b; int r; assert(id); assert(tmp_dir); assert(var_tmp_dir); r = setup_one_tmp_dir(id, "/tmp", &a); if (r < 0) return r; r = setup_one_tmp_dir(id, "/var/tmp", &b); if (r < 0) { char *t; t = strappenda(a, "/tmp"); rmdir(t); rmdir(a); free(a); return r; } *tmp_dir = a; *var_tmp_dir = b; return 0; } int setup_netns(int netns_storage_socket[2]) { _cleanup_close_ int netns = -1; union { struct cmsghdr cmsghdr; uint8_t buf[CMSG_SPACE(sizeof(int))]; } control = {}; struct msghdr mh = { .msg_control = &control, .msg_controllen = sizeof(control), }; struct cmsghdr *cmsg; int r; assert(netns_storage_socket); assert(netns_storage_socket[0] >= 0); assert(netns_storage_socket[1] >= 0); /* We use the passed socketpair as a storage buffer for our * namespace reference fd. Whatever process runs this first * shall create a new namespace, all others should just join * it. To serialize that we use a file lock on the socket * pair. * * It's a bit crazy, but hey, works great! */ if (lockf(netns_storage_socket[0], F_LOCK, 0) < 0) return -errno; if (recvmsg(netns_storage_socket[0], &mh, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) < 0) { if (errno != EAGAIN) { r = -errno; goto fail; } /* Nothing stored yet, so let's create a new namespace */ if (unshare(CLONE_NEWNET) < 0) { r = -errno; goto fail; } loopback_setup(); netns = open("/proc/self/ns/net", O_RDONLY|O_CLOEXEC|O_NOCTTY); if (netns < 0) { r = -errno; goto fail; } r = 1; } else { /* Yay, found something, so let's join the namespace */ for (cmsg = CMSG_FIRSTHDR(&mh); cmsg; cmsg = CMSG_NXTHDR(&mh, cmsg)) { if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) { assert(cmsg->cmsg_len == CMSG_LEN(sizeof(int))); netns = *(int*) CMSG_DATA(cmsg); } } if (setns(netns, CLONE_NEWNET) < 0) { r = -errno; 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; }