[POWERPC] chrp pci_ops: Use named structure member initializers
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / user.c
blobe7d11cef6998fdb378506d72232c4041738dce2f
1 /*
2 * The "user cache".
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.
9 */
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>
21 * UID task count cache, to get fast user lookup in "alloc_uid"
22 * when changing user ID's (ie setuid() and friends).
25 #define UIDHASH_MASK (UIDHASH_SZ - 1)
26 #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
27 #define uidhashentry(ns, uid) ((ns)->uidhash_table + __uidhashfn((uid)))
29 static struct kmem_cache *uid_cachep;
32 * The uidhash_lock is mostly taken from process context, but it is
33 * occasionally also taken from softirq/tasklet context, when
34 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
35 * But free_uid() is also called with local interrupts disabled, and running
36 * local_bh_enable() with local interrupts disabled is an error - we'll run
37 * softirq callbacks, and they can unconditionally enable interrupts, and
38 * the caller of free_uid() didn't expect that..
40 static DEFINE_SPINLOCK(uidhash_lock);
42 struct user_struct root_user = {
43 .__count = ATOMIC_INIT(1),
44 .processes = ATOMIC_INIT(1),
45 .files = ATOMIC_INIT(0),
46 .sigpending = ATOMIC_INIT(0),
47 .mq_bytes = 0,
48 .locked_shm = 0,
49 #ifdef CONFIG_KEYS
50 .uid_keyring = &root_user_keyring,
51 .session_keyring = &root_session_keyring,
52 #endif
56 * These routines must be called with the uidhash spinlock held!
58 static inline void uid_hash_insert(struct user_struct *up, struct list_head *hashent)
60 list_add(&up->uidhash_list, hashent);
63 static inline void uid_hash_remove(struct user_struct *up)
65 list_del(&up->uidhash_list);
68 static inline struct user_struct *uid_hash_find(uid_t uid, struct list_head *hashent)
70 struct list_head *up;
72 list_for_each(up, hashent) {
73 struct user_struct *user;
75 user = list_entry(up, struct user_struct, uidhash_list);
77 if(user->uid == uid) {
78 atomic_inc(&user->__count);
79 return user;
83 return NULL;
87 * Locate the user_struct for the passed UID. If found, take a ref on it. The
88 * caller must undo that ref with free_uid().
90 * If the user_struct could not be found, return NULL.
92 struct user_struct *find_user(uid_t uid)
94 struct user_struct *ret;
95 unsigned long flags;
96 struct user_namespace *ns = current->nsproxy->user_ns;
98 spin_lock_irqsave(&uidhash_lock, flags);
99 ret = uid_hash_find(uid, uidhashentry(ns, uid));
100 spin_unlock_irqrestore(&uidhash_lock, flags);
101 return ret;
104 void free_uid(struct user_struct *up)
106 unsigned long flags;
108 if (!up)
109 return;
111 local_irq_save(flags);
112 if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
113 uid_hash_remove(up);
114 spin_unlock_irqrestore(&uidhash_lock, flags);
115 key_put(up->uid_keyring);
116 key_put(up->session_keyring);
117 kmem_cache_free(uid_cachep, up);
118 } else {
119 local_irq_restore(flags);
123 struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
125 struct list_head *hashent = uidhashentry(ns, uid);
126 struct user_struct *up;
128 spin_lock_irq(&uidhash_lock);
129 up = uid_hash_find(uid, hashent);
130 spin_unlock_irq(&uidhash_lock);
132 if (!up) {
133 struct user_struct *new;
135 new = kmem_cache_alloc(uid_cachep, GFP_KERNEL);
136 if (!new)
137 return NULL;
138 new->uid = uid;
139 atomic_set(&new->__count, 1);
140 atomic_set(&new->processes, 0);
141 atomic_set(&new->files, 0);
142 atomic_set(&new->sigpending, 0);
143 #ifdef CONFIG_INOTIFY_USER
144 atomic_set(&new->inotify_watches, 0);
145 atomic_set(&new->inotify_devs, 0);
146 #endif
148 new->mq_bytes = 0;
149 new->locked_shm = 0;
151 if (alloc_uid_keyring(new, current) < 0) {
152 kmem_cache_free(uid_cachep, new);
153 return NULL;
157 * Before adding this, check whether we raced
158 * on adding the same user already..
160 spin_lock_irq(&uidhash_lock);
161 up = uid_hash_find(uid, hashent);
162 if (up) {
163 key_put(new->uid_keyring);
164 key_put(new->session_keyring);
165 kmem_cache_free(uid_cachep, new);
166 } else {
167 uid_hash_insert(new, hashent);
168 up = new;
170 spin_unlock_irq(&uidhash_lock);
173 return up;
176 void switch_uid(struct user_struct *new_user)
178 struct user_struct *old_user;
180 /* What if a process setreuid()'s and this brings the
181 * new uid over his NPROC rlimit? We can check this now
182 * cheaply with the new uid cache, so if it matters
183 * we should be checking for it. -DaveM
185 old_user = current->user;
186 atomic_inc(&new_user->processes);
187 atomic_dec(&old_user->processes);
188 switch_uid_keyring(new_user);
189 current->user = new_user;
192 * We need to synchronize with __sigqueue_alloc()
193 * doing a get_uid(p->user).. If that saw the old
194 * user value, we need to wait until it has exited
195 * its critical region before we can free the old
196 * structure.
198 smp_mb();
199 spin_unlock_wait(&current->sighand->siglock);
201 free_uid(old_user);
202 suid_keys(current);
206 static int __init uid_cache_init(void)
208 int n;
210 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
211 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
213 for(n = 0; n < UIDHASH_SZ; ++n)
214 INIT_LIST_HEAD(init_user_ns.uidhash_table + n);
216 /* Insert the root user immediately (init already runs as root) */
217 spin_lock_irq(&uidhash_lock);
218 uid_hash_insert(&root_user, uidhashentry(&init_user_ns, 0));
219 spin_unlock_irq(&uidhash_lock);
221 return 0;
224 module_init(uid_cache_init);