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/syscalls.h> 14 #include <linux/err.h> 15 #include <linux/acct.h> 16 #include <linux/slab.h> 17 #include <linux/proc_fs.h> 18 #include <linux/reboot.h> 19 #include <linux/export.h> 20 21 #define BITS_PER_PAGE (PAGE_SIZE*8) 22 23 struct pid_cache { 24 int nr_ids; 25 char name[16]; 26 struct kmem_cache *cachep; 27 struct list_head list; 28 }; 29 30 static LIST_HEAD(pid_caches_lh); 31 static DEFINE_MUTEX(pid_caches_mutex); 32 static struct kmem_cache *pid_ns_cachep; 33 34 /* 35 * creates the kmem cache to allocate pids from. 36 * @nr_ids: the number of numerical ids this pid will have to carry 37 */ 38 39 static struct kmem_cache *create_pid_cachep(int nr_ids) 40 { 41 struct pid_cache *pcache; 42 struct kmem_cache *cachep; 43 44 mutex_lock(&pid_caches_mutex); 45 list_for_each_entry(pcache, &pid_caches_lh, list) 46 if (pcache->nr_ids == nr_ids) 47 goto out; 48 49 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL); 50 if (pcache == NULL) 51 goto err_alloc; 52 53 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids); 54 cachep = kmem_cache_create(pcache->name, 55 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid), 56 0, SLAB_HWCACHE_ALIGN, NULL); 57 if (cachep == NULL) 58 goto err_cachep; 59 60 pcache->nr_ids = nr_ids; 61 pcache->cachep = cachep; 62 list_add(&pcache->list, &pid_caches_lh); 63 out: 64 mutex_unlock(&pid_caches_mutex); 65 return pcache->cachep; 66 67 err_cachep: 68 kfree(pcache); 69 err_alloc: 70 mutex_unlock(&pid_caches_mutex); 71 return NULL; 72 } 73 74 /* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ 75 #define MAX_PID_NS_LEVEL 32 76 77 static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns) 78 { 79 struct pid_namespace *ns; 80 unsigned int level = parent_pid_ns->level + 1; 81 int i; 82 int err; 83 84 if (level > MAX_PID_NS_LEVEL) { 85 err = -EINVAL; 86 goto out; 87 } 88 89 err = -ENOMEM; 90 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); 91 if (ns == NULL) 92 goto out; 93 94 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); 95 if (!ns->pidmap[0].page) 96 goto out_free; 97 98 ns->pid_cachep = create_pid_cachep(level + 1); 99 if (ns->pid_cachep == NULL) 100 goto out_free_map; 101 102 kref_init(&ns->kref); 103 ns->level = level; 104 ns->parent = get_pid_ns(parent_pid_ns); 105 106 set_bit(0, ns->pidmap[0].page); 107 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1); 108 109 for (i = 1; i < PIDMAP_ENTRIES; i++) 110 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE); 111 112 err = pid_ns_prepare_proc(ns); 113 if (err) 114 goto out_put_parent_pid_ns; 115 116 return ns; 117 118 out_put_parent_pid_ns: 119 put_pid_ns(parent_pid_ns); 120 out_free_map: 121 kfree(ns->pidmap[0].page); 122 out_free: 123 kmem_cache_free(pid_ns_cachep, ns); 124 out: 125 return ERR_PTR(err); 126 } 127 128 static void destroy_pid_namespace(struct pid_namespace *ns) 129 { 130 int i; 131 132 for (i = 0; i < PIDMAP_ENTRIES; i++) 133 kfree(ns->pidmap[i].page); 134 kmem_cache_free(pid_ns_cachep, ns); 135 } 136 137 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns) 138 { 139 if (!(flags & CLONE_NEWPID)) 140 return get_pid_ns(old_ns); 141 if (flags & (CLONE_THREAD|CLONE_PARENT)) 142 return ERR_PTR(-EINVAL); 143 return create_pid_namespace(old_ns); 144 } 145 146 static void free_pid_ns(struct kref *kref) 147 { 148 struct pid_namespace *ns; 149 150 ns = container_of(kref, struct pid_namespace, kref); 151 destroy_pid_namespace(ns); 152 } 153 154 void put_pid_ns(struct pid_namespace *ns) 155 { 156 struct pid_namespace *parent; 157 158 while (ns != &init_pid_ns) { 159 parent = ns->parent; 160 if (!kref_put(&ns->kref, free_pid_ns)) 161 break; 162 ns = parent; 163 } 164 } 165 EXPORT_SYMBOL_GPL(put_pid_ns); 166 167 void zap_pid_ns_processes(struct pid_namespace *pid_ns) 168 { 169 int nr; 170 int rc; 171 struct task_struct *task, *me = current; 172 173 /* Ignore SIGCHLD causing any terminated children to autoreap */ 174 spin_lock_irq(&me->sighand->siglock); 175 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN; 176 spin_unlock_irq(&me->sighand->siglock); 177 178 /* 179 * The last thread in the cgroup-init thread group is terminating. 180 * Find remaining pid_ts in the namespace, signal and wait for them 181 * to exit. 182 * 183 * Note: This signals each threads in the namespace - even those that 184 * belong to the same thread group, To avoid this, we would have 185 * to walk the entire tasklist looking a processes in this 186 * namespace, but that could be unnecessarily expensive if the 187 * pid namespace has just a few processes. Or we need to 188 * maintain a tasklist for each pid namespace. 189 * 190 */ 191 read_lock(&tasklist_lock); 192 nr = next_pidmap(pid_ns, 1); 193 while (nr > 0) { 194 rcu_read_lock(); 195 196 task = pid_task(find_vpid(nr), PIDTYPE_PID); 197 if (task && !__fatal_signal_pending(task)) 198 send_sig_info(SIGKILL, SEND_SIG_FORCED, task); 199 200 rcu_read_unlock(); 201 202 nr = next_pidmap(pid_ns, nr); 203 } 204 read_unlock(&tasklist_lock); 205 206 /* Firstly reap the EXIT_ZOMBIE children we may have. */ 207 do { 208 clear_thread_flag(TIF_SIGPENDING); 209 rc = sys_wait4(-1, NULL, __WALL, NULL); 210 } while (rc != -ECHILD); 211 212 /* 213 * sys_wait4() above can't reap the TASK_DEAD children. 214 * Make sure they all go away, see __unhash_process(). 215 */ 216 for (;;) { 217 bool need_wait = false; 218 219 read_lock(&tasklist_lock); 220 if (!list_empty(¤t->children)) { 221 __set_current_state(TASK_UNINTERRUPTIBLE); 222 need_wait = true; 223 } 224 read_unlock(&tasklist_lock); 225 226 if (!need_wait) 227 break; 228 schedule(); 229 } 230 231 if (pid_ns->reboot) 232 current->signal->group_exit_code = pid_ns->reboot; 233 234 acct_exit_ns(pid_ns); 235 return; 236 } 237 238 #ifdef CONFIG_CHECKPOINT_RESTORE 239 static int pid_ns_ctl_handler(struct ctl_table *table, int write, 240 void __user *buffer, size_t *lenp, loff_t *ppos) 241 { 242 struct ctl_table tmp = *table; 243 244 if (write && !capable(CAP_SYS_ADMIN)) 245 return -EPERM; 246 247 /* 248 * Writing directly to ns' last_pid field is OK, since this field 249 * is volatile in a living namespace anyway and a code writing to 250 * it should synchronize its usage with external means. 251 */ 252 253 tmp.data = ¤t->nsproxy->pid_ns->last_pid; 254 return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); 255 } 256 257 extern int pid_max; 258 static int zero = 0; 259 static struct ctl_table pid_ns_ctl_table[] = { 260 { 261 .procname = "ns_last_pid", 262 .maxlen = sizeof(int), 263 .mode = 0666, /* permissions are checked in the handler */ 264 .proc_handler = pid_ns_ctl_handler, 265 .extra1 = &zero, 266 .extra2 = &pid_max, 267 }, 268 { } 269 }; 270 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; 271 #endif /* CONFIG_CHECKPOINT_RESTORE */ 272 273 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) 274 { 275 if (pid_ns == &init_pid_ns) 276 return 0; 277 278 switch (cmd) { 279 case LINUX_REBOOT_CMD_RESTART2: 280 case LINUX_REBOOT_CMD_RESTART: 281 pid_ns->reboot = SIGHUP; 282 break; 283 284 case LINUX_REBOOT_CMD_POWER_OFF: 285 case LINUX_REBOOT_CMD_HALT: 286 pid_ns->reboot = SIGINT; 287 break; 288 default: 289 return -EINVAL; 290 } 291 292 read_lock(&tasklist_lock); 293 force_sig(SIGKILL, pid_ns->child_reaper); 294 read_unlock(&tasklist_lock); 295 296 do_exit(0); 297 298 /* Not reached */ 299 return 0; 300 } 301 302 static __init int pid_namespaces_init(void) 303 { 304 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); 305 306 #ifdef CONFIG_CHECKPOINT_RESTORE 307 register_sysctl_paths(kern_path, pid_ns_ctl_table); 308 #endif 309 return 0; 310 } 311 312 __initcall(pid_namespaces_init); 313