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git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - kernel/user.c
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>
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),
50 .uid_keyring
= &root_user_keyring
,
51 .session_keyring
= &root_session_keyring
,
56 * These routines must be called with the uidhash spinlock held!
58 static inline void uid_hash_insert(struct user_struct
*up
, struct hlist_head
*hashent
)
60 hlist_add_head(&up
->uidhash_node
, hashent
);
63 static inline void uid_hash_remove(struct user_struct
*up
)
65 hlist_del_init(&up
->uidhash_node
);
68 static inline struct user_struct
*uid_hash_find(uid_t uid
, struct hlist_head
*hashent
)
70 struct user_struct
*user
;
73 hlist_for_each_entry(user
, h
, hashent
, uidhash_node
) {
74 if(user
->uid
== uid
) {
75 atomic_inc(&user
->__count
);
84 * Locate the user_struct for the passed UID. If found, take a ref on it. The
85 * caller must undo that ref with free_uid().
87 * If the user_struct could not be found, return NULL.
89 struct user_struct
*find_user(uid_t uid
)
91 struct user_struct
*ret
;
93 struct user_namespace
*ns
= current
->nsproxy
->user_ns
;
95 spin_lock_irqsave(&uidhash_lock
, flags
);
96 ret
= uid_hash_find(uid
, uidhashentry(ns
, uid
));
97 spin_unlock_irqrestore(&uidhash_lock
, flags
);
101 void free_uid(struct user_struct
*up
)
108 local_irq_save(flags
);
109 if (atomic_dec_and_lock(&up
->__count
, &uidhash_lock
)) {
111 spin_unlock_irqrestore(&uidhash_lock
, flags
);
112 key_put(up
->uid_keyring
);
113 key_put(up
->session_keyring
);
114 kmem_cache_free(uid_cachep
, up
);
116 local_irq_restore(flags
);
120 struct user_struct
* alloc_uid(struct user_namespace
*ns
, uid_t uid
)
122 struct hlist_head
*hashent
= uidhashentry(ns
, uid
);
123 struct user_struct
*up
;
125 spin_lock_irq(&uidhash_lock
);
126 up
= uid_hash_find(uid
, hashent
);
127 spin_unlock_irq(&uidhash_lock
);
130 struct user_struct
*new;
132 new = kmem_cache_alloc(uid_cachep
, GFP_KERNEL
);
136 atomic_set(&new->__count
, 1);
137 atomic_set(&new->processes
, 0);
138 atomic_set(&new->files
, 0);
139 atomic_set(&new->sigpending
, 0);
140 #ifdef CONFIG_INOTIFY_USER
141 atomic_set(&new->inotify_watches
, 0);
142 atomic_set(&new->inotify_devs
, 0);
148 if (alloc_uid_keyring(new, current
) < 0) {
149 kmem_cache_free(uid_cachep
, new);
154 * Before adding this, check whether we raced
155 * on adding the same user already..
157 spin_lock_irq(&uidhash_lock
);
158 up
= uid_hash_find(uid
, hashent
);
160 key_put(new->uid_keyring
);
161 key_put(new->session_keyring
);
162 kmem_cache_free(uid_cachep
, new);
164 uid_hash_insert(new, hashent
);
167 spin_unlock_irq(&uidhash_lock
);
173 void switch_uid(struct user_struct
*new_user
)
175 struct user_struct
*old_user
;
177 /* What if a process setreuid()'s and this brings the
178 * new uid over his NPROC rlimit? We can check this now
179 * cheaply with the new uid cache, so if it matters
180 * we should be checking for it. -DaveM
182 old_user
= current
->user
;
183 atomic_inc(&new_user
->processes
);
184 atomic_dec(&old_user
->processes
);
185 switch_uid_keyring(new_user
);
186 current
->user
= new_user
;
189 * We need to synchronize with __sigqueue_alloc()
190 * doing a get_uid(p->user).. If that saw the old
191 * user value, we need to wait until it has exited
192 * its critical region before we can free the old
196 spin_unlock_wait(¤t
->sighand
->siglock
);
202 void release_uids(struct user_namespace
*ns
)
206 struct hlist_head
*head
;
207 struct hlist_node
*nd
;
209 spin_lock_irqsave(&uidhash_lock
, flags
);
211 * collapse the chains so that the user_struct-s will
212 * be still alive, but not in hashes. subsequent free_uid()
215 for (i
= 0; i
< UIDHASH_SZ
; i
++) {
216 head
= ns
->uidhash_table
+ i
;
217 while (!hlist_empty(head
)) {
222 spin_unlock_irqrestore(&uidhash_lock
, flags
);
224 free_uid(ns
->root_user
);
227 static int __init
uid_cache_init(void)
231 uid_cachep
= kmem_cache_create("uid_cache", sizeof(struct user_struct
),
232 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
);
234 for(n
= 0; n
< UIDHASH_SZ
; ++n
)
235 INIT_HLIST_HEAD(init_user_ns
.uidhash_table
+ n
);
237 /* Insert the root user immediately (init already runs as root) */
238 spin_lock_irq(&uidhash_lock
);
239 uid_hash_insert(&root_user
, uidhashentry(&init_user_ns
, 0));
240 spin_unlock_irq(&uidhash_lock
);
245 module_init(uid_cache_init
);