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 20 #define BITS_PER_PAGE (PAGE_SIZE*8) 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 struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns) 74 { 75 struct pid_namespace *ns; 76 unsigned int level = parent_pid_ns->level + 1; 77 int i, err = -ENOMEM; 78 79 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); 80 if (ns == NULL) 81 goto out; 82 83 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); 84 if (!ns->pidmap[0].page) 85 goto out_free; 86 87 ns->pid_cachep = create_pid_cachep(level + 1); 88 if (ns->pid_cachep == NULL) 89 goto out_free_map; 90 91 kref_init(&ns->kref); 92 ns->level = level; 93 ns->parent = get_pid_ns(parent_pid_ns); 94 95 set_bit(0, ns->pidmap[0].page); 96 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1); 97 98 for (i = 1; i < PIDMAP_ENTRIES; i++) 99 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE); 100 101 err = pid_ns_prepare_proc(ns); 102 if (err) 103 goto out_put_parent_pid_ns; 104 105 return ns; 106 107 out_put_parent_pid_ns: 108 put_pid_ns(parent_pid_ns); 109 out_free_map: 110 kfree(ns->pidmap[0].page); 111 out_free: 112 kmem_cache_free(pid_ns_cachep, ns); 113 out: 114 return ERR_PTR(err); 115 } 116 117 static void destroy_pid_namespace(struct pid_namespace *ns) 118 { 119 int i; 120 121 for (i = 0; i < PIDMAP_ENTRIES; i++) 122 kfree(ns->pidmap[i].page); 123 kmem_cache_free(pid_ns_cachep, ns); 124 } 125 126 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns) 127 { 128 if (!(flags & CLONE_NEWPID)) 129 return get_pid_ns(old_ns); 130 if (flags & (CLONE_THREAD|CLONE_PARENT)) 131 return ERR_PTR(-EINVAL); 132 return create_pid_namespace(old_ns); 133 } 134 135 void free_pid_ns(struct kref *kref) 136 { 137 struct pid_namespace *ns, *parent; 138 139 ns = container_of(kref, struct pid_namespace, kref); 140 141 parent = ns->parent; 142 destroy_pid_namespace(ns); 143 144 if (parent != NULL) 145 put_pid_ns(parent); 146 } 147 148 void zap_pid_ns_processes(struct pid_namespace *pid_ns) 149 { 150 int nr; 151 int rc; 152 struct task_struct *task, *me = current; 153 154 /* Ignore SIGCHLD causing any terminated children to autoreap */ 155 spin_lock_irq(&me->sighand->siglock); 156 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN; 157 spin_unlock_irq(&me->sighand->siglock); 158 159 /* 160 * The last thread in the cgroup-init thread group is terminating. 161 * Find remaining pid_ts in the namespace, signal and wait for them 162 * to exit. 163 * 164 * Note: This signals each threads in the namespace - even those that 165 * belong to the same thread group, To avoid this, we would have 166 * to walk the entire tasklist looking a processes in this 167 * namespace, but that could be unnecessarily expensive if the 168 * pid namespace has just a few processes. Or we need to 169 * maintain a tasklist for each pid namespace. 170 * 171 */ 172 read_lock(&tasklist_lock); 173 nr = next_pidmap(pid_ns, 1); 174 while (nr > 0) { 175 rcu_read_lock(); 176 177 task = pid_task(find_vpid(nr), PIDTYPE_PID); 178 if (task && !__fatal_signal_pending(task)) 179 send_sig_info(SIGKILL, SEND_SIG_FORCED, task); 180 181 rcu_read_unlock(); 182 183 nr = next_pidmap(pid_ns, nr); 184 } 185 read_unlock(&tasklist_lock); 186 187 do { 188 clear_thread_flag(TIF_SIGPENDING); 189 rc = sys_wait4(-1, NULL, __WALL, NULL); 190 } while (rc != -ECHILD); 191 192 if (pid_ns->reboot) 193 current->signal->group_exit_code = pid_ns->reboot; 194 195 acct_exit_ns(pid_ns); 196 return; 197 } 198 199 #ifdef CONFIG_CHECKPOINT_RESTORE 200 static int pid_ns_ctl_handler(struct ctl_table *table, int write, 201 void __user *buffer, size_t *lenp, loff_t *ppos) 202 { 203 struct ctl_table tmp = *table; 204 205 if (write && !capable(CAP_SYS_ADMIN)) 206 return -EPERM; 207 208 /* 209 * Writing directly to ns' last_pid field is OK, since this field 210 * is volatile in a living namespace anyway and a code writing to 211 * it should synchronize its usage with external means. 212 */ 213 214 tmp.data = ¤t->nsproxy->pid_ns->last_pid; 215 return proc_dointvec(&tmp, write, buffer, lenp, ppos); 216 } 217 218 static struct ctl_table pid_ns_ctl_table[] = { 219 { 220 .procname = "ns_last_pid", 221 .maxlen = sizeof(int), 222 .mode = 0666, /* permissions are checked in the handler */ 223 .proc_handler = pid_ns_ctl_handler, 224 }, 225 { } 226 }; 227 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; 228 #endif /* CONFIG_CHECKPOINT_RESTORE */ 229 230 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) 231 { 232 if (pid_ns == &init_pid_ns) 233 return 0; 234 235 switch (cmd) { 236 case LINUX_REBOOT_CMD_RESTART2: 237 case LINUX_REBOOT_CMD_RESTART: 238 pid_ns->reboot = SIGHUP; 239 break; 240 241 case LINUX_REBOOT_CMD_POWER_OFF: 242 case LINUX_REBOOT_CMD_HALT: 243 pid_ns->reboot = SIGINT; 244 break; 245 default: 246 return -EINVAL; 247 } 248 249 read_lock(&tasklist_lock); 250 force_sig(SIGKILL, pid_ns->child_reaper); 251 read_unlock(&tasklist_lock); 252 253 do_exit(0); 254 255 /* Not reached */ 256 return 0; 257 } 258 259 static __init int pid_namespaces_init(void) 260 { 261 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); 262 263 #ifdef CONFIG_CHECKPOINT_RESTORE 264 register_sysctl_paths(kern_path, pid_ns_ctl_table); 265 #endif 266 return 0; 267 } 268 269 __initcall(pid_namespaces_init); 270