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