1 /* 2 * Pid namespaces 3 * 4 * Authors: 5 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc. 6 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM 7 * Many thanks to Oleg Nesterov for comments and help 8 * 9 */ 10 11 #include <linux/pid.h> 12 #include <linux/pid_namespace.h> 13 #include <linux/user_namespace.h> 14 #include <linux/syscalls.h> 15 #include <linux/err.h> 16 #include <linux/acct.h> 17 #include <linux/slab.h> 18 #include <linux/proc_ns.h> 19 #include <linux/reboot.h> 20 #include <linux/export.h> 21 22 struct pid_cache { 23 int nr_ids; 24 char name[16]; 25 struct kmem_cache *cachep; 26 struct list_head list; 27 }; 28 29 static LIST_HEAD(pid_caches_lh); 30 static DEFINE_MUTEX(pid_caches_mutex); 31 static struct kmem_cache *pid_ns_cachep; 32 33 /* 34 * creates the kmem cache to allocate pids from. 35 * @nr_ids: the number of numerical ids this pid will have to carry 36 */ 37 38 static struct kmem_cache *create_pid_cachep(int nr_ids) 39 { 40 struct pid_cache *pcache; 41 struct kmem_cache *cachep; 42 43 mutex_lock(&pid_caches_mutex); 44 list_for_each_entry(pcache, &pid_caches_lh, list) 45 if (pcache->nr_ids == nr_ids) 46 goto out; 47 48 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL); 49 if (pcache == NULL) 50 goto err_alloc; 51 52 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids); 53 cachep = kmem_cache_create(pcache->name, 54 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid), 55 0, SLAB_HWCACHE_ALIGN, NULL); 56 if (cachep == NULL) 57 goto err_cachep; 58 59 pcache->nr_ids = nr_ids; 60 pcache->cachep = cachep; 61 list_add(&pcache->list, &pid_caches_lh); 62 out: 63 mutex_unlock(&pid_caches_mutex); 64 return pcache->cachep; 65 66 err_cachep: 67 kfree(pcache); 68 err_alloc: 69 mutex_unlock(&pid_caches_mutex); 70 return NULL; 71 } 72 73 static void proc_cleanup_work(struct work_struct *work) 74 { 75 struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work); 76 pid_ns_release_proc(ns); 77 } 78 79 /* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ 80 #define MAX_PID_NS_LEVEL 32 81 82 static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns, 83 struct pid_namespace *parent_pid_ns) 84 { 85 struct pid_namespace *ns; 86 unsigned int level = parent_pid_ns->level + 1; 87 int i; 88 int err; 89 90 if (level > MAX_PID_NS_LEVEL) { 91 err = -EINVAL; 92 goto out; 93 } 94 95 err = -ENOMEM; 96 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); 97 if (ns == NULL) 98 goto out; 99 100 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); 101 if (!ns->pidmap[0].page) 102 goto out_free; 103 104 ns->pid_cachep = create_pid_cachep(level + 1); 105 if (ns->pid_cachep == NULL) 106 goto out_free_map; 107 108 err = proc_alloc_inum(&ns->proc_inum); 109 if (err) 110 goto out_free_map; 111 112 kref_init(&ns->kref); 113 ns->level = level; 114 ns->parent = get_pid_ns(parent_pid_ns); 115 ns->user_ns = get_user_ns(user_ns); 116 ns->nr_hashed = PIDNS_HASH_ADDING; 117 INIT_WORK(&ns->proc_work, proc_cleanup_work); 118 119 set_bit(0, ns->pidmap[0].page); 120 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1); 121 122 for (i = 1; i < PIDMAP_ENTRIES; i++) 123 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE); 124 125 return ns; 126 127 out_free_map: 128 kfree(ns->pidmap[0].page); 129 out_free: 130 kmem_cache_free(pid_ns_cachep, ns); 131 out: 132 return ERR_PTR(err); 133 } 134 135 static void destroy_pid_namespace(struct pid_namespace *ns) 136 { 137 int i; 138 139 proc_free_inum(ns->proc_inum); 140 for (i = 0; i < PIDMAP_ENTRIES; i++) 141 kfree(ns->pidmap[i].page); 142 put_user_ns(ns->user_ns); 143 kmem_cache_free(pid_ns_cachep, ns); 144 } 145 146 struct pid_namespace *copy_pid_ns(unsigned long flags, 147 struct user_namespace *user_ns, struct pid_namespace *old_ns) 148 { 149 if (!(flags & CLONE_NEWPID)) 150 return get_pid_ns(old_ns); 151 if (task_active_pid_ns(current) != old_ns) 152 return ERR_PTR(-EINVAL); 153 return create_pid_namespace(user_ns, old_ns); 154 } 155 156 static void free_pid_ns(struct kref *kref) 157 { 158 struct pid_namespace *ns; 159 160 ns = container_of(kref, struct pid_namespace, kref); 161 destroy_pid_namespace(ns); 162 } 163 164 void put_pid_ns(struct pid_namespace *ns) 165 { 166 struct pid_namespace *parent; 167 168 while (ns != &init_pid_ns) { 169 parent = ns->parent; 170 if (!kref_put(&ns->kref, free_pid_ns)) 171 break; 172 ns = parent; 173 } 174 } 175 EXPORT_SYMBOL_GPL(put_pid_ns); 176 177 void zap_pid_ns_processes(struct pid_namespace *pid_ns) 178 { 179 int nr; 180 int rc; 181 struct task_struct *task, *me = current; 182 int init_pids = thread_group_leader(me) ? 1 : 2; 183 184 /* Don't allow any more processes into the pid namespace */ 185 disable_pid_allocation(pid_ns); 186 187 /* Ignore SIGCHLD causing any terminated children to autoreap */ 188 spin_lock_irq(&me->sighand->siglock); 189 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN; 190 spin_unlock_irq(&me->sighand->siglock); 191 192 /* 193 * The last thread in the cgroup-init thread group is terminating. 194 * Find remaining pid_ts in the namespace, signal and wait for them 195 * to exit. 196 * 197 * Note: This signals each threads in the namespace - even those that 198 * belong to the same thread group, To avoid this, we would have 199 * to walk the entire tasklist looking a processes in this 200 * namespace, but that could be unnecessarily expensive if the 201 * pid namespace has just a few processes. Or we need to 202 * maintain a tasklist for each pid namespace. 203 * 204 */ 205 read_lock(&tasklist_lock); 206 nr = next_pidmap(pid_ns, 1); 207 while (nr > 0) { 208 rcu_read_lock(); 209 210 task = pid_task(find_vpid(nr), PIDTYPE_PID); 211 if (task && !__fatal_signal_pending(task)) 212 send_sig_info(SIGKILL, SEND_SIG_FORCED, task); 213 214 rcu_read_unlock(); 215 216 nr = next_pidmap(pid_ns, nr); 217 } 218 read_unlock(&tasklist_lock); 219 220 /* Firstly reap the EXIT_ZOMBIE children we may have. */ 221 do { 222 clear_thread_flag(TIF_SIGPENDING); 223 rc = sys_wait4(-1, NULL, __WALL, NULL); 224 } while (rc != -ECHILD); 225 226 /* 227 * sys_wait4() above can't reap the TASK_DEAD children. 228 * Make sure they all go away, see free_pid(). 229 */ 230 for (;;) { 231 set_current_state(TASK_UNINTERRUPTIBLE); 232 if (pid_ns->nr_hashed == init_pids) 233 break; 234 schedule(); 235 } 236 __set_current_state(TASK_RUNNING); 237 238 if (pid_ns->reboot) 239 current->signal->group_exit_code = pid_ns->reboot; 240 241 acct_exit_ns(pid_ns); 242 return; 243 } 244 245 #ifdef CONFIG_CHECKPOINT_RESTORE 246 static int pid_ns_ctl_handler(struct ctl_table *table, int write, 247 void __user *buffer, size_t *lenp, loff_t *ppos) 248 { 249 struct pid_namespace *pid_ns = task_active_pid_ns(current); 250 struct ctl_table tmp = *table; 251 252 if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN)) 253 return -EPERM; 254 255 /* 256 * Writing directly to ns' last_pid field is OK, since this field 257 * is volatile in a living namespace anyway and a code writing to 258 * it should synchronize its usage with external means. 259 */ 260 261 tmp.data = &pid_ns->last_pid; 262 return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); 263 } 264 265 extern int pid_max; 266 static int zero = 0; 267 static struct ctl_table pid_ns_ctl_table[] = { 268 { 269 .procname = "ns_last_pid", 270 .maxlen = sizeof(int), 271 .mode = 0666, /* permissions are checked in the handler */ 272 .proc_handler = pid_ns_ctl_handler, 273 .extra1 = &zero, 274 .extra2 = &pid_max, 275 }, 276 { } 277 }; 278 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; 279 #endif /* CONFIG_CHECKPOINT_RESTORE */ 280 281 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) 282 { 283 if (pid_ns == &init_pid_ns) 284 return 0; 285 286 switch (cmd) { 287 case LINUX_REBOOT_CMD_RESTART2: 288 case LINUX_REBOOT_CMD_RESTART: 289 pid_ns->reboot = SIGHUP; 290 break; 291 292 case LINUX_REBOOT_CMD_POWER_OFF: 293 case LINUX_REBOOT_CMD_HALT: 294 pid_ns->reboot = SIGINT; 295 break; 296 default: 297 return -EINVAL; 298 } 299 300 read_lock(&tasklist_lock); 301 force_sig(SIGKILL, pid_ns->child_reaper); 302 read_unlock(&tasklist_lock); 303 304 do_exit(0); 305 306 /* Not reached */ 307 return 0; 308 } 309 310 static void *pidns_get(struct task_struct *task) 311 { 312 struct pid_namespace *ns; 313 314 rcu_read_lock(); 315 ns = get_pid_ns(task_active_pid_ns(task)); 316 rcu_read_unlock(); 317 318 return ns; 319 } 320 321 static void pidns_put(void *ns) 322 { 323 put_pid_ns(ns); 324 } 325 326 static int pidns_install(struct nsproxy *nsproxy, void *ns) 327 { 328 struct pid_namespace *active = task_active_pid_ns(current); 329 struct pid_namespace *ancestor, *new = ns; 330 331 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) || 332 !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) 333 return -EPERM; 334 335 /* 336 * Only allow entering the current active pid namespace 337 * or a child of the current active pid namespace. 338 * 339 * This is required for fork to return a usable pid value and 340 * this maintains the property that processes and their 341 * children can not escape their current pid namespace. 342 */ 343 if (new->level < active->level) 344 return -EINVAL; 345 346 ancestor = new; 347 while (ancestor->level > active->level) 348 ancestor = ancestor->parent; 349 if (ancestor != active) 350 return -EINVAL; 351 352 put_pid_ns(nsproxy->pid_ns_for_children); 353 nsproxy->pid_ns_for_children = get_pid_ns(new); 354 return 0; 355 } 356 357 static unsigned int pidns_inum(void *ns) 358 { 359 struct pid_namespace *pid_ns = ns; 360 return pid_ns->proc_inum; 361 } 362 363 const struct proc_ns_operations pidns_operations = { 364 .name = "pid", 365 .type = CLONE_NEWPID, 366 .get = pidns_get, 367 .put = pidns_put, 368 .install = pidns_install, 369 .inum = pidns_inum, 370 }; 371 372 static __init int pid_namespaces_init(void) 373 { 374 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); 375 376 #ifdef CONFIG_CHECKPOINT_RESTORE 377 register_sysctl_paths(kern_path, pid_ns_ctl_table); 378 #endif 379 return 0; 380 } 381 382 __initcall(pid_namespaces_init); 383