/*-*- 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 "strv.h" #include "util.h" #include "path-util.h" #include "namespace.h" #include "missing.h" #include "execute.h" typedef enum MountMode { /* This is ordered by priority! */ INACCESSIBLE, READONLY, PRIVATE_TMP, PRIVATE_VAR_TMP, READWRITE } MountMode; typedef struct BindMount { const char *path; MountMode mode; bool done; } BindMount; static int append_mounts(BindMount **p, char **strv, MountMode mode) { char **i; STRV_FOREACH(i, strv) { 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 apply_mount( BindMount *m, const char *tmp_dir, const char *var_tmp_dir) { const char *what; int r; assert(m); switch (m->mode) { 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); 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) return -errno; return 0; } int setup_tmpdirs(char **tmp_dir, char **var_tmp_dir) { int r = 0; char tmp_dir_template[] = "/tmp/systemd-private-XXXXXX", var_tmp_dir_template[] = "/var/tmp/systemd-private-XXXXXX"; assert(tmp_dir); assert(var_tmp_dir); r = create_tmp_dir(tmp_dir_template, tmp_dir); if (r < 0) return r; r = create_tmp_dir(var_tmp_dir_template, var_tmp_dir); if (r == 0) return 0; /* failure */ rmdir(*tmp_dir); rmdir(tmp_dir_template); free(*tmp_dir); *tmp_dir = NULL; return r; } int setup_namespace(char** read_write_dirs, char** read_only_dirs, char** inaccessible_dirs, char* tmp_dir, char* var_tmp_dir, bool private_tmp, unsigned mount_flags) { unsigned n = strv_length(read_write_dirs) + strv_length(read_only_dirs) + strv_length(inaccessible_dirs) + (private_tmp ? 2 : 0); BindMount *m, *mounts; int r = 0; if (!mount_flags) mount_flags = MS_SHARED; if (unshare(CLONE_NEWNS) < 0) return -errno; m = mounts = (BindMount *) alloca(n * sizeof(BindMount)); if ((r = append_mounts(&m, read_write_dirs, READWRITE)) < 0 || (r = append_mounts(&m, read_only_dirs, READONLY)) < 0 || (r = append_mounts(&m, inaccessible_dirs, INACCESSIBLE)) < 0) return r; if (private_tmp) { m->path = "/tmp"; m->mode = PRIVATE_TMP; m++; m->path = "/var/tmp"; m->mode = PRIVATE_VAR_TMP; 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 undo_mounts; } for (m = mounts; m < mounts + n; ++m) { r = make_read_only(m); if (r < 0) goto undo_mounts; } /* Remount / as the desired mode */ if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) { r = -errno; goto undo_mounts; } return 0; undo_mounts: for (m = mounts; m < mounts + n; ++m) { if (m->done) umount2(m->path, MNT_DETACH); } return r; }