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 19 #define BITS_PER_PAGE (PAGE_SIZE*8) 20 21 struct pid_cache { 22 int nr_ids; 23 char name[16]; 24 struct kmem_cache *cachep; 25 struct list_head list; 26 }; 27 28 static LIST_HEAD(pid_caches_lh); 29 static DEFINE_MUTEX(pid_caches_mutex); 30 static struct kmem_cache *pid_ns_cachep; 31 32 /* 33 * creates the kmem cache to allocate pids from. 34 * @nr_ids: the number of numerical ids this pid will have to carry 35 */ 36 37 static struct kmem_cache *create_pid_cachep(int nr_ids) 38 { 39 struct pid_cache *pcache; 40 struct kmem_cache *cachep; 41 42 mutex_lock(&pid_caches_mutex); 43 list_for_each_entry(pcache, &pid_caches_lh, list) 44 if (pcache->nr_ids == nr_ids) 45 goto out; 46 47 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL); 48 if (pcache == NULL) 49 goto err_alloc; 50 51 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids); 52 cachep = kmem_cache_create(pcache->name, 53 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid), 54 0, SLAB_HWCACHE_ALIGN, NULL); 55 if (cachep == NULL) 56 goto err_cachep; 57 58 pcache->nr_ids = nr_ids; 59 pcache->cachep = cachep; 60 list_add(&pcache->list, &pid_caches_lh); 61 out: 62 mutex_unlock(&pid_caches_mutex); 63 return pcache->cachep; 64 65 err_cachep: 66 kfree(pcache); 67 err_alloc: 68 mutex_unlock(&pid_caches_mutex); 69 return NULL; 70 } 71 72 static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns) 73 { 74 struct pid_namespace *ns; 75 unsigned int level = parent_pid_ns->level + 1; 76 int i, err = -ENOMEM; 77 78 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); 79 if (ns == NULL) 80 goto out; 81 82 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); 83 if (!ns->pidmap[0].page) 84 goto out_free; 85 86 ns->pid_cachep = create_pid_cachep(level + 1); 87 if (ns->pid_cachep == NULL) 88 goto out_free_map; 89 90 kref_init(&ns->kref); 91 ns->level = level; 92 ns->parent = get_pid_ns(parent_pid_ns); 93 94 set_bit(0, ns->pidmap[0].page); 95 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1); 96 97 for (i = 1; i < PIDMAP_ENTRIES; i++) 98 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE); 99 100 err = pid_ns_prepare_proc(ns); 101 if (err) 102 goto out_put_parent_pid_ns; 103 104 return ns; 105 106 out_put_parent_pid_ns: 107 put_pid_ns(parent_pid_ns); 108 out_free_map: 109 kfree(ns->pidmap[0].page); 110 out_free: 111 kmem_cache_free(pid_ns_cachep, ns); 112 out: 113 return ERR_PTR(err); 114 } 115 116 static void destroy_pid_namespace(struct pid_namespace *ns) 117 { 118 int i; 119 120 for (i = 0; i < PIDMAP_ENTRIES; i++) 121 kfree(ns->pidmap[i].page); 122 kmem_cache_free(pid_ns_cachep, ns); 123 } 124 125 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns) 126 { 127 if (!(flags & CLONE_NEWPID)) 128 return get_pid_ns(old_ns); 129 if (flags & (CLONE_THREAD|CLONE_PARENT)) 130 return ERR_PTR(-EINVAL); 131 return create_pid_namespace(old_ns); 132 } 133 134 void free_pid_ns(struct kref *kref) 135 { 136 struct pid_namespace *ns, *parent; 137 138 ns = container_of(kref, struct pid_namespace, kref); 139 140 parent = ns->parent; 141 destroy_pid_namespace(ns); 142 143 if (parent != NULL) 144 put_pid_ns(parent); 145 } 146 147 void zap_pid_ns_processes(struct pid_namespace *pid_ns) 148 { 149 int nr; 150 int rc; 151 struct task_struct *task; 152 153 /* 154 * The last thread in the cgroup-init thread group is terminating. 155 * Find remaining pid_ts in the namespace, signal and wait for them 156 * to exit. 157 * 158 * Note: This signals each threads in the namespace - even those that 159 * belong to the same thread group, To avoid this, we would have 160 * to walk the entire tasklist looking a processes in this 161 * namespace, but that could be unnecessarily expensive if the 162 * pid namespace has just a few processes. Or we need to 163 * maintain a tasklist for each pid namespace. 164 * 165 */ 166 read_lock(&tasklist_lock); 167 nr = next_pidmap(pid_ns, 1); 168 while (nr > 0) { 169 rcu_read_lock(); 170 171 /* 172 * Any nested-container's init processes won't ignore the 173 * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser(). 174 */ 175 task = pid_task(find_vpid(nr), PIDTYPE_PID); 176 if (task) 177 send_sig_info(SIGKILL, SEND_SIG_NOINFO, task); 178 179 rcu_read_unlock(); 180 181 nr = next_pidmap(pid_ns, nr); 182 } 183 read_unlock(&tasklist_lock); 184 185 do { 186 clear_thread_flag(TIF_SIGPENDING); 187 rc = sys_wait4(-1, NULL, __WALL, NULL); 188 } while (rc != -ECHILD); 189 190 acct_exit_ns(pid_ns); 191 return; 192 } 193 194 static int pid_ns_ctl_handler(struct ctl_table *table, int write, 195 void __user *buffer, size_t *lenp, loff_t *ppos) 196 { 197 struct ctl_table tmp = *table; 198 199 if (write && !capable(CAP_SYS_ADMIN)) 200 return -EPERM; 201 202 /* 203 * Writing directly to ns' last_pid field is OK, since this field 204 * is volatile in a living namespace anyway and a code writing to 205 * it should synchronize its usage with external means. 206 */ 207 208 tmp.data = ¤t->nsproxy->pid_ns->last_pid; 209 return proc_dointvec(&tmp, write, buffer, lenp, ppos); 210 } 211 212 static struct ctl_table pid_ns_ctl_table[] = { 213 { 214 .procname = "ns_last_pid", 215 .maxlen = sizeof(int), 216 .mode = 0666, /* permissions are checked in the handler */ 217 .proc_handler = pid_ns_ctl_handler, 218 }, 219 { } 220 }; 221 222 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; 223 224 static __init int pid_namespaces_init(void) 225 { 226 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); 227 register_sysctl_paths(kern_path, pid_ns_ctl_table); 228 return 0; 229 } 230 231 __initcall(pid_namespaces_init); 232