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git.proxmox.com Git - mirror_ubuntu-eoan-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>
19 * UID task count cache, to get fast user lookup in "alloc_uid"
20 * when changing user ID's (ie setuid() and friends).
23 #define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 8)
24 #define UIDHASH_SZ (1 << UIDHASH_BITS)
25 #define UIDHASH_MASK (UIDHASH_SZ - 1)
26 #define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
27 #define uidhashentry(uid) (uidhash_table + __uidhashfn((uid)))
29 static kmem_cache_t
*uid_cachep
;
30 static struct list_head uidhash_table
[UIDHASH_SZ
];
33 * The uidhash_lock is mostly taken from process context, but it is
34 * occasionally also taken from softirq/tasklet context, when
35 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
36 * But free_uid() is also called with local interrupts disabled, and running
37 * local_bh_enable() with local interrupts disabled is an error - we'll run
38 * softirq callbacks, and they can unconditionally enable interrupts, and
39 * the caller of free_uid() didn't expect that..
41 static DEFINE_SPINLOCK(uidhash_lock
);
43 struct user_struct root_user
= {
44 .__count
= ATOMIC_INIT(1),
45 .processes
= ATOMIC_INIT(1),
46 .files
= ATOMIC_INIT(0),
47 .sigpending
= ATOMIC_INIT(0),
51 .uid_keyring
= &root_user_keyring
,
52 .session_keyring
= &root_session_keyring
,
57 * These routines must be called with the uidhash spinlock held!
59 static inline void uid_hash_insert(struct user_struct
*up
, struct list_head
*hashent
)
61 list_add(&up
->uidhash_list
, hashent
);
64 static inline void uid_hash_remove(struct user_struct
*up
)
66 list_del(&up
->uidhash_list
);
69 static inline struct user_struct
*uid_hash_find(uid_t uid
, struct list_head
*hashent
)
73 list_for_each(up
, hashent
) {
74 struct user_struct
*user
;
76 user
= list_entry(up
, struct user_struct
, uidhash_list
);
78 if(user
->uid
== uid
) {
79 atomic_inc(&user
->__count
);
88 * Locate the user_struct for the passed UID. If found, take a ref on it. The
89 * caller must undo that ref with free_uid().
91 * If the user_struct could not be found, return NULL.
93 struct user_struct
*find_user(uid_t uid
)
95 struct user_struct
*ret
;
98 spin_lock_irqsave(&uidhash_lock
, flags
);
99 ret
= uid_hash_find(uid
, uidhashentry(uid
));
100 spin_unlock_irqrestore(&uidhash_lock
, flags
);
104 void free_uid(struct user_struct
*up
)
111 local_irq_save(flags
);
112 if (atomic_dec_and_lock(&up
->__count
, &uidhash_lock
)) {
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
);
119 local_irq_restore(flags
);
123 struct user_struct
* alloc_uid(uid_t uid
)
125 struct list_head
*hashent
= uidhashentry(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
);
133 struct user_struct
*new;
135 new = kmem_cache_alloc(uid_cachep
, SLAB_KERNEL
);
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);
151 if (alloc_uid_keyring(new, current
) < 0) {
152 kmem_cache_free(uid_cachep
, new);
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
);
163 key_put(new->uid_keyring
);
164 key_put(new->session_keyring
);
165 kmem_cache_free(uid_cachep
, new);
167 uid_hash_insert(new, hashent
);
170 spin_unlock_irq(&uidhash_lock
);
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
;
195 static int __init
uid_cache_init(void)
199 uid_cachep
= kmem_cache_create("uid_cache", sizeof(struct user_struct
),
200 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
, NULL
, NULL
);
202 for(n
= 0; n
< UIDHASH_SZ
; ++n
)
203 INIT_LIST_HEAD(uidhash_table
+ n
);
205 /* Insert the root user immediately (init already runs as root) */
206 spin_lock_irq(&uidhash_lock
);
207 uid_hash_insert(&root_user
, uidhashentry(0));
208 spin_unlock_irq(&uidhash_lock
);
213 module_init(uid_cache_init
);