powerpc/mm/4k: don't allocate larger pmd page table for 4k
[linux/fpc-iii.git] / security / keys / gc.c
blobaddf060399e09547307d9c023f36d8dbf869a931
1 /* Key garbage collector
3 * Copyright (C) 2009-2011 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
12 #include <linux/module.h>
13 #include <linux/slab.h>
14 #include <linux/security.h>
15 #include <keys/keyring-type.h>
16 #include "internal.h"
19 * Delay between key revocation/expiry in seconds
21 unsigned key_gc_delay = 5 * 60;
24 * Reaper for unused keys.
26 static void key_garbage_collector(struct work_struct *work);
27 DECLARE_WORK(key_gc_work, key_garbage_collector);
30 * Reaper for links from keyrings to dead keys.
32 static void key_gc_timer_func(unsigned long);
33 static DEFINE_TIMER(key_gc_timer, key_gc_timer_func, 0, 0);
35 static time_t key_gc_next_run = LONG_MAX;
36 static struct key_type *key_gc_dead_keytype;
38 static unsigned long key_gc_flags;
39 #define KEY_GC_KEY_EXPIRED 0 /* A key expired and needs unlinking */
40 #define KEY_GC_REAP_KEYTYPE 1 /* A keytype is being unregistered */
41 #define KEY_GC_REAPING_KEYTYPE 2 /* Cleared when keytype reaped */
45 * Any key whose type gets unregistered will be re-typed to this if it can't be
46 * immediately unlinked.
48 struct key_type key_type_dead = {
49 .name = "dead",
53 * Schedule a garbage collection run.
54 * - time precision isn't particularly important
56 void key_schedule_gc(time_t gc_at)
58 unsigned long expires;
59 time_t now = current_kernel_time().tv_sec;
61 kenter("%ld", gc_at - now);
63 if (gc_at <= now || test_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) {
64 kdebug("IMMEDIATE");
65 schedule_work(&key_gc_work);
66 } else if (gc_at < key_gc_next_run) {
67 kdebug("DEFERRED");
68 key_gc_next_run = gc_at;
69 expires = jiffies + (gc_at - now) * HZ;
70 mod_timer(&key_gc_timer, expires);
75 * Schedule a dead links collection run.
77 void key_schedule_gc_links(void)
79 set_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags);
80 schedule_work(&key_gc_work);
84 * Some key's cleanup time was met after it expired, so we need to get the
85 * reaper to go through a cycle finding expired keys.
87 static void key_gc_timer_func(unsigned long data)
89 kenter("");
90 key_gc_next_run = LONG_MAX;
91 key_schedule_gc_links();
95 * Reap keys of dead type.
97 * We use three flags to make sure we see three complete cycles of the garbage
98 * collector: the first to mark keys of that type as being dead, the second to
99 * collect dead links and the third to clean up the dead keys. We have to be
100 * careful as there may already be a cycle in progress.
102 * The caller must be holding key_types_sem.
104 void key_gc_keytype(struct key_type *ktype)
106 kenter("%s", ktype->name);
108 key_gc_dead_keytype = ktype;
109 set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
110 smp_mb();
111 set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags);
113 kdebug("schedule");
114 schedule_work(&key_gc_work);
116 kdebug("sleep");
117 wait_on_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE,
118 TASK_UNINTERRUPTIBLE);
120 key_gc_dead_keytype = NULL;
121 kleave("");
125 * Garbage collect a list of unreferenced, detached keys
127 static noinline void key_gc_unused_keys(struct list_head *keys)
129 while (!list_empty(keys)) {
130 struct key *key =
131 list_entry(keys->next, struct key, graveyard_link);
132 list_del(&key->graveyard_link);
134 kdebug("- %u", key->serial);
135 key_check(key);
137 /* Throw away the key data if the key is instantiated */
138 if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
139 !test_bit(KEY_FLAG_NEGATIVE, &key->flags) &&
140 key->type->destroy)
141 key->type->destroy(key);
143 security_key_free(key);
145 /* deal with the user's key tracking and quota */
146 if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
147 spin_lock(&key->user->lock);
148 key->user->qnkeys--;
149 key->user->qnbytes -= key->quotalen;
150 spin_unlock(&key->user->lock);
153 atomic_dec(&key->user->nkeys);
154 if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
155 atomic_dec(&key->user->nikeys);
157 key_user_put(key->user);
159 kfree(key->description);
161 #ifdef KEY_DEBUGGING
162 key->magic = KEY_DEBUG_MAGIC_X;
163 #endif
164 kmem_cache_free(key_jar, key);
169 * Garbage collector for unused keys.
171 * This is done in process context so that we don't have to disable interrupts
172 * all over the place. key_put() schedules this rather than trying to do the
173 * cleanup itself, which means key_put() doesn't have to sleep.
175 static void key_garbage_collector(struct work_struct *work)
177 static LIST_HEAD(graveyard);
178 static u8 gc_state; /* Internal persistent state */
179 #define KEY_GC_REAP_AGAIN 0x01 /* - Need another cycle */
180 #define KEY_GC_REAPING_LINKS 0x02 /* - We need to reap links */
181 #define KEY_GC_SET_TIMER 0x04 /* - We need to restart the timer */
182 #define KEY_GC_REAPING_DEAD_1 0x10 /* - We need to mark dead keys */
183 #define KEY_GC_REAPING_DEAD_2 0x20 /* - We need to reap dead key links */
184 #define KEY_GC_REAPING_DEAD_3 0x40 /* - We need to reap dead keys */
185 #define KEY_GC_FOUND_DEAD_KEY 0x80 /* - We found at least one dead key */
187 struct rb_node *cursor;
188 struct key *key;
189 time_t new_timer, limit;
191 kenter("[%lx,%x]", key_gc_flags, gc_state);
193 limit = current_kernel_time().tv_sec;
194 if (limit > key_gc_delay)
195 limit -= key_gc_delay;
196 else
197 limit = key_gc_delay;
199 /* Work out what we're going to be doing in this pass */
200 gc_state &= KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2;
201 gc_state <<= 1;
202 if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags))
203 gc_state |= KEY_GC_REAPING_LINKS | KEY_GC_SET_TIMER;
205 if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags))
206 gc_state |= KEY_GC_REAPING_DEAD_1;
207 kdebug("new pass %x", gc_state);
209 new_timer = LONG_MAX;
211 /* As only this function is permitted to remove things from the key
212 * serial tree, if cursor is non-NULL then it will always point to a
213 * valid node in the tree - even if lock got dropped.
215 spin_lock(&key_serial_lock);
216 cursor = rb_first(&key_serial_tree);
218 continue_scanning:
219 while (cursor) {
220 key = rb_entry(cursor, struct key, serial_node);
221 cursor = rb_next(cursor);
223 if (atomic_read(&key->usage) == 0)
224 goto found_unreferenced_key;
226 if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) {
227 if (key->type == key_gc_dead_keytype) {
228 gc_state |= KEY_GC_FOUND_DEAD_KEY;
229 set_bit(KEY_FLAG_DEAD, &key->flags);
230 key->perm = 0;
231 goto skip_dead_key;
235 if (gc_state & KEY_GC_SET_TIMER) {
236 if (key->expiry > limit && key->expiry < new_timer) {
237 kdebug("will expire %x in %ld",
238 key_serial(key), key->expiry - limit);
239 new_timer = key->expiry;
243 if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2))
244 if (key->type == key_gc_dead_keytype)
245 gc_state |= KEY_GC_FOUND_DEAD_KEY;
247 if ((gc_state & KEY_GC_REAPING_LINKS) ||
248 unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) {
249 if (key->type == &key_type_keyring)
250 goto found_keyring;
253 if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3))
254 if (key->type == key_gc_dead_keytype)
255 goto destroy_dead_key;
257 skip_dead_key:
258 if (spin_is_contended(&key_serial_lock) || need_resched())
259 goto contended;
262 contended:
263 spin_unlock(&key_serial_lock);
265 maybe_resched:
266 if (cursor) {
267 cond_resched();
268 spin_lock(&key_serial_lock);
269 goto continue_scanning;
272 /* We've completed the pass. Set the timer if we need to and queue a
273 * new cycle if necessary. We keep executing cycles until we find one
274 * where we didn't reap any keys.
276 kdebug("pass complete");
278 if (gc_state & KEY_GC_SET_TIMER && new_timer != (time_t)LONG_MAX) {
279 new_timer += key_gc_delay;
280 key_schedule_gc(new_timer);
283 if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2) ||
284 !list_empty(&graveyard)) {
285 /* Make sure that all pending keyring payload destructions are
286 * fulfilled and that people aren't now looking at dead or
287 * dying keys that they don't have a reference upon or a link
288 * to.
290 kdebug("gc sync");
291 synchronize_rcu();
294 if (!list_empty(&graveyard)) {
295 kdebug("gc keys");
296 key_gc_unused_keys(&graveyard);
299 if (unlikely(gc_state & (KEY_GC_REAPING_DEAD_1 |
300 KEY_GC_REAPING_DEAD_2))) {
301 if (!(gc_state & KEY_GC_FOUND_DEAD_KEY)) {
302 /* No remaining dead keys: short circuit the remaining
303 * keytype reap cycles.
305 kdebug("dead short");
306 gc_state &= ~(KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2);
307 gc_state |= KEY_GC_REAPING_DEAD_3;
308 } else {
309 gc_state |= KEY_GC_REAP_AGAIN;
313 if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) {
314 kdebug("dead wake");
315 smp_mb();
316 clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
317 wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE);
320 if (gc_state & KEY_GC_REAP_AGAIN)
321 schedule_work(&key_gc_work);
322 kleave(" [end %x]", gc_state);
323 return;
325 /* We found an unreferenced key - once we've removed it from the tree,
326 * we can safely drop the lock.
328 found_unreferenced_key:
329 kdebug("unrefd key %d", key->serial);
330 rb_erase(&key->serial_node, &key_serial_tree);
331 spin_unlock(&key_serial_lock);
333 list_add_tail(&key->graveyard_link, &graveyard);
334 gc_state |= KEY_GC_REAP_AGAIN;
335 goto maybe_resched;
337 /* We found a keyring and we need to check the payload for links to
338 * dead or expired keys. We don't flag another reap immediately as we
339 * have to wait for the old payload to be destroyed by RCU before we
340 * can reap the keys to which it refers.
342 found_keyring:
343 spin_unlock(&key_serial_lock);
344 keyring_gc(key, limit);
345 goto maybe_resched;
347 /* We found a dead key that is still referenced. Reset its type and
348 * destroy its payload with its semaphore held.
350 destroy_dead_key:
351 spin_unlock(&key_serial_lock);
352 kdebug("destroy key %d", key->serial);
353 down_write(&key->sem);
354 key->type = &key_type_dead;
355 if (key_gc_dead_keytype->destroy)
356 key_gc_dead_keytype->destroy(key);
357 memset(&key->payload, KEY_DESTROY, sizeof(key->payload));
358 up_write(&key->sem);
359 goto maybe_resched;