4 * (C) Copyright 1991-2000 Linus Torvalds
6 * We have a per-user structure to keep track of how many
7 * processes, files etc the user has claimed, in order to be
8 * able to have per-user limits for system resources.
11 #include <linux/init.h>
12 #include <linux/sched.h>
13 #include <linux/slab.h>
14 #include <linux/bitops.h>
15 #include <linux/key.h>
16 #include <linux/interrupt.h>
17 #include <linux/module.h>
18 #include <linux/user_namespace.h>
19 #include "cred-internals.h"
21 struct user_namespace init_user_ns = {
23 .refcount = ATOMIC_INIT(1),
25 .creator = &root_user,
27 EXPORT_SYMBOL_GPL(init_user_ns);
30 * UID task count cache, to get fast user lookup in "alloc_uid"
31 * when changing user ID's (ie setuid() and friends).
34 #define UIDHASH_MASK (UIDHASH_SZ - 1)
35 #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
36 #define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
38 static struct kmem_cache *uid_cachep;
41 * The uidhash_lock is mostly taken from process context, but it is
42 * occasionally also taken from softirq/tasklet context, when
43 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
44 * But free_uid() is also called with local interrupts disabled, and running
45 * local_bh_enable() with local interrupts disabled is an error - we'll run
46 * softirq callbacks, and they can unconditionally enable interrupts, and
47 * the caller of free_uid() didn't expect that..
49 static DEFINE_SPINLOCK(uidhash_lock);
51 /* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->creator */
52 struct user_struct root_user = {
53 .__count = ATOMIC_INIT(2),
54 .processes = ATOMIC_INIT(1),
55 .files = ATOMIC_INIT(0),
56 .sigpending = ATOMIC_INIT(0),
58 .user_ns = &init_user_ns,
59 #ifdef CONFIG_USER_SCHED
60 .tg = &init_task_group,
65 * These routines must be called with the uidhash spinlock held!
67 static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
69 hlist_add_head(&up->uidhash_node, hashent);
72 static void uid_hash_remove(struct user_struct *up)
74 hlist_del_init(&up->uidhash_node);
77 static struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
79 struct user_struct *user;
82 hlist_for_each_entry(user, h, hashent, uidhash_node) {
83 if (user->uid == uid) {
84 atomic_inc(&user->__count);
92 #ifdef CONFIG_USER_SCHED
94 static void sched_destroy_user(struct user_struct *up)
96 sched_destroy_group(up->tg);
99 static int sched_create_user(struct user_struct *up)
103 up->tg = sched_create_group(&root_task_group);
110 #else /* CONFIG_USER_SCHED */
112 static void sched_destroy_user(struct user_struct *up) { }
113 static int sched_create_user(struct user_struct *up) { return 0; }
115 #endif /* CONFIG_USER_SCHED */
117 #if defined(CONFIG_USER_SCHED) && defined(CONFIG_SYSFS)
119 static struct kset *uids_kset; /* represents the /sys/kernel/uids/ directory */
120 static DEFINE_MUTEX(uids_mutex);
122 static inline void uids_mutex_lock(void)
124 mutex_lock(&uids_mutex);
127 static inline void uids_mutex_unlock(void)
129 mutex_unlock(&uids_mutex);
132 /* uid directory attributes */
133 #ifdef CONFIG_FAIR_GROUP_SCHED
134 static ssize_t cpu_shares_show(struct kobject *kobj,
135 struct kobj_attribute *attr,
138 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
140 return sprintf(buf, "%lu\n", sched_group_shares(up->tg));
143 static ssize_t cpu_shares_store(struct kobject *kobj,
144 struct kobj_attribute *attr,
145 const char *buf, size_t size)
147 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
148 unsigned long shares;
151 sscanf(buf, "%lu", &shares);
153 rc = sched_group_set_shares(up->tg, shares);
155 return (rc ? rc : size);
158 static struct kobj_attribute cpu_share_attr =
159 __ATTR(cpu_share, 0644, cpu_shares_show, cpu_shares_store);
162 #ifdef CONFIG_RT_GROUP_SCHED
163 static ssize_t cpu_rt_runtime_show(struct kobject *kobj,
164 struct kobj_attribute *attr,
167 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
169 return sprintf(buf, "%ld\n", sched_group_rt_runtime(up->tg));
172 static ssize_t cpu_rt_runtime_store(struct kobject *kobj,
173 struct kobj_attribute *attr,
174 const char *buf, size_t size)
176 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
177 unsigned long rt_runtime;
180 sscanf(buf, "%ld", &rt_runtime);
182 rc = sched_group_set_rt_runtime(up->tg, rt_runtime);
184 return (rc ? rc : size);
187 static struct kobj_attribute cpu_rt_runtime_attr =
188 __ATTR(cpu_rt_runtime, 0644, cpu_rt_runtime_show, cpu_rt_runtime_store);
190 static ssize_t cpu_rt_period_show(struct kobject *kobj,
191 struct kobj_attribute *attr,
194 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
196 return sprintf(buf, "%lu\n", sched_group_rt_period(up->tg));
199 static ssize_t cpu_rt_period_store(struct kobject *kobj,
200 struct kobj_attribute *attr,
201 const char *buf, size_t size)
203 struct user_struct *up = container_of(kobj, struct user_struct, kobj);
204 unsigned long rt_period;
207 sscanf(buf, "%lu", &rt_period);
209 rc = sched_group_set_rt_period(up->tg, rt_period);
211 return (rc ? rc : size);
214 static struct kobj_attribute cpu_rt_period_attr =
215 __ATTR(cpu_rt_period, 0644, cpu_rt_period_show, cpu_rt_period_store);
218 /* default attributes per uid directory */
219 static struct attribute *uids_attributes[] = {
220 #ifdef CONFIG_FAIR_GROUP_SCHED
221 &cpu_share_attr.attr,
223 #ifdef CONFIG_RT_GROUP_SCHED
224 &cpu_rt_runtime_attr.attr,
225 &cpu_rt_period_attr.attr,
230 /* the lifetime of user_struct is not managed by the core (now) */
231 static void uids_release(struct kobject *kobj)
236 static struct kobj_type uids_ktype = {
237 .sysfs_ops = &kobj_sysfs_ops,
238 .default_attrs = uids_attributes,
239 .release = uids_release,
242 /* create /sys/kernel/uids/<uid>/cpu_share file for this user */
243 static int uids_user_create(struct user_struct *up)
245 struct kobject *kobj = &up->kobj;
248 memset(kobj, 0, sizeof(struct kobject));
249 kobj->kset = uids_kset;
250 error = kobject_init_and_add(kobj, &uids_ktype, NULL, "%d", up->uid);
256 kobject_uevent(kobj, KOBJ_ADD);
261 /* create these entries in sysfs:
262 * "/sys/kernel/uids" directory
263 * "/sys/kernel/uids/0" directory (for root user)
264 * "/sys/kernel/uids/0/cpu_share" file (for root user)
266 int __init uids_sysfs_init(void)
268 uids_kset = kset_create_and_add("uids", NULL, kernel_kobj);
272 return uids_user_create(&root_user);
275 /* work function to remove sysfs directory for a user and free up
276 * corresponding structures.
278 static void remove_user_sysfs_dir(struct work_struct *w)
280 struct user_struct *up = container_of(w, struct user_struct, work);
284 /* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
289 local_irq_save(flags);
291 if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
294 spin_unlock_irqrestore(&uidhash_lock, flags);
296 local_irq_restore(flags);
302 kobject_uevent(&up->kobj, KOBJ_REMOVE);
303 kobject_del(&up->kobj);
304 kobject_put(&up->kobj);
306 sched_destroy_user(up);
307 key_put(up->uid_keyring);
308 key_put(up->session_keyring);
309 kmem_cache_free(uid_cachep, up);
315 /* IRQs are disabled and uidhash_lock is held upon function entry.
316 * IRQ state (as stored in flags) is restored and uidhash_lock released
317 * upon function exit.
319 static void free_user(struct user_struct *up, unsigned long flags)
321 /* restore back the count */
322 atomic_inc(&up->__count);
323 spin_unlock_irqrestore(&uidhash_lock, flags);
325 put_user_ns(up->user_ns);
326 INIT_WORK(&up->work, remove_user_sysfs_dir);
327 schedule_work(&up->work);
330 #else /* CONFIG_USER_SCHED && CONFIG_SYSFS */
332 int uids_sysfs_init(void) { return 0; }
333 static inline int uids_user_create(struct user_struct *up) { return 0; }
334 static inline void uids_mutex_lock(void) { }
335 static inline void uids_mutex_unlock(void) { }
337 /* IRQs are disabled and uidhash_lock is held upon function entry.
338 * IRQ state (as stored in flags) is restored and uidhash_lock released
339 * upon function exit.
341 static void free_user(struct user_struct *up, unsigned long flags)
344 spin_unlock_irqrestore(&uidhash_lock, flags);
345 sched_destroy_user(up);
346 key_put(up->uid_keyring);
347 key_put(up->session_keyring);
348 put_user_ns(up->user_ns);
349 kmem_cache_free(uid_cachep, up);
355 * Locate the user_struct for the passed UID. If found, take a ref on it. The
356 * caller must undo that ref with free_uid().
358 * If the user_struct could not be found, return NULL.
360 struct user_struct *find_user(uid_t uid)
362 struct user_struct *ret;
364 struct user_namespace *ns = current_user_ns();
366 spin_lock_irqsave(&uidhash_lock, flags);
367 ret = uid_hash_find(uid, uidhashentry(ns, uid));
368 spin_unlock_irqrestore(&uidhash_lock, flags);
372 void free_uid(struct user_struct *up)
379 local_irq_save(flags);
380 if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
381 free_user(up, flags);
383 local_irq_restore(flags);
386 struct user_struct *alloc_uid(struct user_namespace *ns, uid_t uid)
388 struct hlist_head *hashent = uidhashentry(ns, uid);
389 struct user_struct *up, *new;
391 /* Make uid_hash_find() + uids_user_create() + uid_hash_insert()
396 spin_lock_irq(&uidhash_lock);
397 up = uid_hash_find(uid, hashent);
398 spin_unlock_irq(&uidhash_lock);
401 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
406 atomic_set(&new->__count, 1);
408 if (sched_create_user(new) < 0)
411 new->user_ns = get_user_ns(ns);
413 if (uids_user_create(new))
414 goto out_destoy_sched;
417 * Before adding this, check whether we raced
418 * on adding the same user already..
420 spin_lock_irq(&uidhash_lock);
421 up = uid_hash_find(uid, hashent);
423 /* This case is not possible when CONFIG_USER_SCHED
424 * is defined, since we serialize alloc_uid() using
425 * uids_mutex. Hence no need to call
426 * sched_destroy_user() or remove_user_sysfs_dir().
428 key_put(new->uid_keyring);
429 key_put(new->session_keyring);
430 kmem_cache_free(uid_cachep, new);
432 uid_hash_insert(new, hashent);
435 spin_unlock_irq(&uidhash_lock);
443 sched_destroy_user(new);
444 put_user_ns(new->user_ns);
446 kmem_cache_free(uid_cachep, new);
452 static int __init uid_cache_init(void)
456 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
457 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
459 for(n = 0; n < UIDHASH_SZ; ++n)
460 INIT_HLIST_HEAD(init_user_ns.uidhash_table + n);
462 /* Insert the root user immediately (init already runs as root) */
463 spin_lock_irq(&uidhash_lock);
464 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
465 spin_unlock_irq(&uidhash_lock);
470 module_init(uid_cache_init);