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 void free_pid_ns(struct kref *kref) 137 { 138 struct pid_namespace *ns, *parent; 139 140 ns = container_of(kref, struct pid_namespace, kref); 141 142 parent = ns->parent; 143 destroy_pid_namespace(ns); 144 145 if (parent != NULL) 146 put_pid_ns(parent); 147 } 148 EXPORT_SYMBOL_GPL(free_pid_ns); 149 150 void zap_pid_ns_processes(struct pid_namespace *pid_ns) 151 { 152 int nr; 153 int rc; 154 struct task_struct *task, *me = current; 155 156 /* Ignore SIGCHLD causing any terminated children to autoreap */ 157 spin_lock_irq(&me->sighand->siglock); 158 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN; 159 spin_unlock_irq(&me->sighand->siglock); 160 161 /* 162 * The last thread in the cgroup-init thread group is terminating. 163 * Find remaining pid_ts in the namespace, signal and wait for them 164 * to exit. 165 * 166 * Note: This signals each threads in the namespace - even those that 167 * belong to the same thread group, To avoid this, we would have 168 * to walk the entire tasklist looking a processes in this 169 * namespace, but that could be unnecessarily expensive if the 170 * pid namespace has just a few processes. Or we need to 171 * maintain a tasklist for each pid namespace. 172 * 173 */ 174 read_lock(&tasklist_lock); 175 nr = next_pidmap(pid_ns, 1); 176 while (nr > 0) { 177 rcu_read_lock(); 178 179 task = pid_task(find_vpid(nr), PIDTYPE_PID); 180 if (task && !__fatal_signal_pending(task)) 181 send_sig_info(SIGKILL, SEND_SIG_FORCED, task); 182 183 rcu_read_unlock(); 184 185 nr = next_pidmap(pid_ns, nr); 186 } 187 read_unlock(&tasklist_lock); 188 189 /* Firstly reap the EXIT_ZOMBIE children we may have. */ 190 do { 191 clear_thread_flag(TIF_SIGPENDING); 192 rc = sys_wait4(-1, NULL, __WALL, NULL); 193 } while (rc != -ECHILD); 194 195 /* 196 * sys_wait4() above can't reap the TASK_DEAD children. 197 * Make sure they all go away, see __unhash_process(). 198 */ 199 for (;;) { 200 bool need_wait = false; 201 202 read_lock(&tasklist_lock); 203 if (!list_empty(¤t->children)) { 204 __set_current_state(TASK_UNINTERRUPTIBLE); 205 need_wait = true; 206 } 207 read_unlock(&tasklist_lock); 208 209 if (!need_wait) 210 break; 211 schedule(); 212 } 213 214 if (pid_ns->reboot) 215 current->signal->group_exit_code = pid_ns->reboot; 216 217 acct_exit_ns(pid_ns); 218 return; 219 } 220 221 #ifdef CONFIG_CHECKPOINT_RESTORE 222 static int pid_ns_ctl_handler(struct ctl_table *table, int write, 223 void __user *buffer, size_t *lenp, loff_t *ppos) 224 { 225 struct ctl_table tmp = *table; 226 227 if (write && !capable(CAP_SYS_ADMIN)) 228 return -EPERM; 229 230 /* 231 * Writing directly to ns' last_pid field is OK, since this field 232 * is volatile in a living namespace anyway and a code writing to 233 * it should synchronize its usage with external means. 234 */ 235 236 tmp.data = ¤t->nsproxy->pid_ns->last_pid; 237 return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); 238 } 239 240 extern int pid_max; 241 static int zero = 0; 242 static struct ctl_table pid_ns_ctl_table[] = { 243 { 244 .procname = "ns_last_pid", 245 .maxlen = sizeof(int), 246 .mode = 0666, /* permissions are checked in the handler */ 247 .proc_handler = pid_ns_ctl_handler, 248 .extra1 = &zero, 249 .extra2 = &pid_max, 250 }, 251 { } 252 }; 253 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; 254 #endif /* CONFIG_CHECKPOINT_RESTORE */ 255 256 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) 257 { 258 if (pid_ns == &init_pid_ns) 259 return 0; 260 261 switch (cmd) { 262 case LINUX_REBOOT_CMD_RESTART2: 263 case LINUX_REBOOT_CMD_RESTART: 264 pid_ns->reboot = SIGHUP; 265 break; 266 267 case LINUX_REBOOT_CMD_POWER_OFF: 268 case LINUX_REBOOT_CMD_HALT: 269 pid_ns->reboot = SIGINT; 270 break; 271 default: 272 return -EINVAL; 273 } 274 275 read_lock(&tasklist_lock); 276 force_sig(SIGKILL, pid_ns->child_reaper); 277 read_unlock(&tasklist_lock); 278 279 do_exit(0); 280 281 /* Not reached */ 282 return 0; 283 } 284 285 static __init int pid_namespaces_init(void) 286 { 287 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); 288 289 #ifdef CONFIG_CHECKPOINT_RESTORE 290 register_sysctl_paths(kern_path, pid_ns_ctl_table); 291 #endif 292 return 0; 293 } 294 295 __initcall(pid_namespaces_init); 296