Commit | Line | Data |
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5d135440 DH |
1 | /* Key garbage collector |
2 | * | |
0c061b57 | 3 | * Copyright (C) 2009-2011 Red Hat, Inc. All Rights Reserved. |
5d135440 DH |
4 | * Written by David Howells (dhowells@redhat.com) |
5 | * | |
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. | |
10 | */ | |
11 | ||
8bc16dea DH |
12 | #include <linux/slab.h> |
13 | #include <linux/security.h> | |
5d135440 DH |
14 | #include <keys/keyring-type.h> |
15 | #include "internal.h" | |
16 | ||
17 | /* | |
18 | * Delay between key revocation/expiry in seconds | |
19 | */ | |
20 | unsigned key_gc_delay = 5 * 60; | |
21 | ||
22 | /* | |
8bc16dea DH |
23 | * Reaper for unused keys. |
24 | */ | |
0c061b57 DH |
25 | static void key_garbage_collector(struct work_struct *work); |
26 | DECLARE_WORK(key_gc_work, key_garbage_collector); | |
8bc16dea DH |
27 | |
28 | /* | |
29 | * Reaper for links from keyrings to dead keys. | |
5d135440 | 30 | */ |
24ed960a | 31 | static void key_gc_timer_func(struct timer_list *); |
1d27e3e2 | 32 | static DEFINE_TIMER(key_gc_timer, key_gc_timer_func); |
0c061b57 | 33 | |
074d5898 | 34 | static time64_t key_gc_next_run = TIME64_MAX; |
0c061b57 DH |
35 | static struct key_type *key_gc_dead_keytype; |
36 | ||
37 | static unsigned long key_gc_flags; | |
38 | #define KEY_GC_KEY_EXPIRED 0 /* A key expired and needs unlinking */ | |
39 | #define KEY_GC_REAP_KEYTYPE 1 /* A keytype is being unregistered */ | |
40 | #define KEY_GC_REAPING_KEYTYPE 2 /* Cleared when keytype reaped */ | |
41 | ||
42 | ||
43 | /* | |
44 | * Any key whose type gets unregistered will be re-typed to this if it can't be | |
45 | * immediately unlinked. | |
46 | */ | |
47 | struct key_type key_type_dead = { | |
c1644fe0 | 48 | .name = ".dead", |
0c061b57 | 49 | }; |
5d135440 DH |
50 | |
51 | /* | |
973c9f4f DH |
52 | * Schedule a garbage collection run. |
53 | * - time precision isn't particularly important | |
5d135440 | 54 | */ |
074d5898 | 55 | void key_schedule_gc(time64_t gc_at) |
5d135440 DH |
56 | { |
57 | unsigned long expires; | |
074d5898 | 58 | time64_t now = ktime_get_real_seconds(); |
5d135440 | 59 | |
074d5898 | 60 | kenter("%lld", gc_at - now); |
5d135440 | 61 | |
0c061b57 DH |
62 | if (gc_at <= now || test_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) { |
63 | kdebug("IMMEDIATE"); | |
3b07e9ca | 64 | schedule_work(&key_gc_work); |
5d135440 | 65 | } else if (gc_at < key_gc_next_run) { |
0c061b57 DH |
66 | kdebug("DEFERRED"); |
67 | key_gc_next_run = gc_at; | |
5d135440 DH |
68 | expires = jiffies + (gc_at - now) * HZ; |
69 | mod_timer(&key_gc_timer, expires); | |
70 | } | |
71 | } | |
72 | ||
fd75815f DH |
73 | /* |
74 | * Schedule a dead links collection run. | |
75 | */ | |
76 | void key_schedule_gc_links(void) | |
77 | { | |
78 | set_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags); | |
3b07e9ca | 79 | schedule_work(&key_gc_work); |
fd75815f DH |
80 | } |
81 | ||
5d135440 | 82 | /* |
0c061b57 DH |
83 | * Some key's cleanup time was met after it expired, so we need to get the |
84 | * reaper to go through a cycle finding expired keys. | |
5d135440 | 85 | */ |
24ed960a | 86 | static void key_gc_timer_func(struct timer_list *unused) |
5d135440 DH |
87 | { |
88 | kenter(""); | |
074d5898 | 89 | key_gc_next_run = TIME64_MAX; |
fd75815f | 90 | key_schedule_gc_links(); |
5d135440 DH |
91 | } |
92 | ||
0c061b57 DH |
93 | /* |
94 | * Reap keys of dead type. | |
95 | * | |
96 | * We use three flags to make sure we see three complete cycles of the garbage | |
97 | * collector: the first to mark keys of that type as being dead, the second to | |
98 | * collect dead links and the third to clean up the dead keys. We have to be | |
99 | * careful as there may already be a cycle in progress. | |
100 | * | |
101 | * The caller must be holding key_types_sem. | |
102 | */ | |
103 | void key_gc_keytype(struct key_type *ktype) | |
104 | { | |
105 | kenter("%s", ktype->name); | |
106 | ||
107 | key_gc_dead_keytype = ktype; | |
108 | set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); | |
109 | smp_mb(); | |
110 | set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags); | |
111 | ||
112 | kdebug("schedule"); | |
3b07e9ca | 113 | schedule_work(&key_gc_work); |
0c061b57 DH |
114 | |
115 | kdebug("sleep"); | |
74316201 | 116 | wait_on_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE, |
0c061b57 DH |
117 | TASK_UNINTERRUPTIBLE); |
118 | ||
119 | key_gc_dead_keytype = NULL; | |
120 | kleave(""); | |
121 | } | |
122 | ||
5d135440 | 123 | /* |
65d87fe6 | 124 | * Garbage collect a list of unreferenced, detached keys |
5d135440 | 125 | */ |
65d87fe6 | 126 | static noinline void key_gc_unused_keys(struct list_head *keys) |
5d135440 | 127 | { |
65d87fe6 DH |
128 | while (!list_empty(keys)) { |
129 | struct key *key = | |
130 | list_entry(keys->next, struct key, graveyard_link); | |
363b02da DH |
131 | short state = key->state; |
132 | ||
65d87fe6 DH |
133 | list_del(&key->graveyard_link); |
134 | ||
135 | kdebug("- %u", key->serial); | |
136 | key_check(key); | |
137 | ||
f05819df | 138 | /* Throw away the key data if the key is instantiated */ |
363b02da | 139 | if (state == KEY_IS_POSITIVE && key->type->destroy) |
94c4554b DH |
140 | key->type->destroy(key); |
141 | ||
65d87fe6 DH |
142 | security_key_free(key); |
143 | ||
144 | /* deal with the user's key tracking and quota */ | |
145 | if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) { | |
146 | spin_lock(&key->user->lock); | |
147 | key->user->qnkeys--; | |
148 | key->user->qnbytes -= key->quotalen; | |
149 | spin_unlock(&key->user->lock); | |
150 | } | |
5d135440 | 151 | |
65d87fe6 | 152 | atomic_dec(&key->user->nkeys); |
363b02da | 153 | if (state != KEY_IS_UNINSTANTIATED) |
65d87fe6 | 154 | atomic_dec(&key->user->nikeys); |
5d135440 | 155 | |
a3a87844 SL |
156 | key_user_put(key->user); |
157 | ||
65d87fe6 | 158 | kfree(key->description); |
5d135440 | 159 | |
0620fddb | 160 | memzero_explicit(key, sizeof(*key)); |
65d87fe6 DH |
161 | kmem_cache_free(key_jar, key); |
162 | } | |
5d135440 | 163 | } |
8bc16dea DH |
164 | |
165 | /* | |
166 | * Garbage collector for unused keys. | |
167 | * | |
168 | * This is done in process context so that we don't have to disable interrupts | |
169 | * all over the place. key_put() schedules this rather than trying to do the | |
170 | * cleanup itself, which means key_put() doesn't have to sleep. | |
171 | */ | |
0c061b57 | 172 | static void key_garbage_collector(struct work_struct *work) |
8bc16dea | 173 | { |
65d87fe6 | 174 | static LIST_HEAD(graveyard); |
0c061b57 DH |
175 | static u8 gc_state; /* Internal persistent state */ |
176 | #define KEY_GC_REAP_AGAIN 0x01 /* - Need another cycle */ | |
177 | #define KEY_GC_REAPING_LINKS 0x02 /* - We need to reap links */ | |
178 | #define KEY_GC_SET_TIMER 0x04 /* - We need to restart the timer */ | |
179 | #define KEY_GC_REAPING_DEAD_1 0x10 /* - We need to mark dead keys */ | |
180 | #define KEY_GC_REAPING_DEAD_2 0x20 /* - We need to reap dead key links */ | |
181 | #define KEY_GC_REAPING_DEAD_3 0x40 /* - We need to reap dead keys */ | |
182 | #define KEY_GC_FOUND_DEAD_KEY 0x80 /* - We found at least one dead key */ | |
183 | ||
184 | struct rb_node *cursor; | |
8bc16dea | 185 | struct key *key; |
074d5898 | 186 | time64_t new_timer, limit; |
0c061b57 DH |
187 | |
188 | kenter("[%lx,%x]", key_gc_flags, gc_state); | |
189 | ||
074d5898 | 190 | limit = ktime_get_real_seconds(); |
0c061b57 DH |
191 | if (limit > key_gc_delay) |
192 | limit -= key_gc_delay; | |
193 | else | |
194 | limit = key_gc_delay; | |
195 | ||
196 | /* Work out what we're going to be doing in this pass */ | |
197 | gc_state &= KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2; | |
198 | gc_state <<= 1; | |
199 | if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags)) | |
200 | gc_state |= KEY_GC_REAPING_LINKS | KEY_GC_SET_TIMER; | |
201 | ||
202 | if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) | |
203 | gc_state |= KEY_GC_REAPING_DEAD_1; | |
204 | kdebug("new pass %x", gc_state); | |
205 | ||
074d5898 | 206 | new_timer = TIME64_MAX; |
8bc16dea | 207 | |
0c061b57 DH |
208 | /* As only this function is permitted to remove things from the key |
209 | * serial tree, if cursor is non-NULL then it will always point to a | |
210 | * valid node in the tree - even if lock got dropped. | |
211 | */ | |
8bc16dea | 212 | spin_lock(&key_serial_lock); |
0c061b57 | 213 | cursor = rb_first(&key_serial_tree); |
8bc16dea | 214 | |
0c061b57 DH |
215 | continue_scanning: |
216 | while (cursor) { | |
217 | key = rb_entry(cursor, struct key, serial_node); | |
218 | cursor = rb_next(cursor); | |
8bc16dea | 219 | |
fff29291 | 220 | if (refcount_read(&key->usage) == 0) |
0c061b57 DH |
221 | goto found_unreferenced_key; |
222 | ||
223 | if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) { | |
224 | if (key->type == key_gc_dead_keytype) { | |
225 | gc_state |= KEY_GC_FOUND_DEAD_KEY; | |
226 | set_bit(KEY_FLAG_DEAD, &key->flags); | |
227 | key->perm = 0; | |
228 | goto skip_dead_key; | |
2b6aa412 MM |
229 | } else if (key->type == &key_type_keyring && |
230 | key->restrict_link) { | |
231 | goto found_restricted_keyring; | |
0c061b57 DH |
232 | } |
233 | } | |
234 | ||
235 | if (gc_state & KEY_GC_SET_TIMER) { | |
236 | if (key->expiry > limit && key->expiry < new_timer) { | |
074d5898 | 237 | kdebug("will expire %x in %lld", |
0c061b57 DH |
238 | key_serial(key), key->expiry - limit); |
239 | new_timer = key->expiry; | |
240 | } | |
241 | } | |
242 | ||
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; | |
246 | ||
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; | |
251 | } | |
252 | ||
253 | if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) | |
254 | if (key->type == key_gc_dead_keytype) | |
255 | goto destroy_dead_key; | |
256 | ||
257 | skip_dead_key: | |
258 | if (spin_is_contended(&key_serial_lock) || need_resched()) | |
259 | goto contended; | |
8bc16dea DH |
260 | } |
261 | ||
0c061b57 | 262 | contended: |
8bc16dea | 263 | spin_unlock(&key_serial_lock); |
8bc16dea | 264 | |
0c061b57 DH |
265 | maybe_resched: |
266 | if (cursor) { | |
267 | cond_resched(); | |
268 | spin_lock(&key_serial_lock); | |
269 | goto continue_scanning; | |
270 | } | |
8bc16dea | 271 | |
0c061b57 DH |
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. | |
275 | */ | |
276 | kdebug("pass complete"); | |
8bc16dea | 277 | |
074d5898 | 278 | if (gc_state & KEY_GC_SET_TIMER && new_timer != (time64_t)TIME64_MAX) { |
0c061b57 DH |
279 | new_timer += key_gc_delay; |
280 | key_schedule_gc(new_timer); | |
281 | } | |
8bc16dea | 282 | |
65d87fe6 DH |
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. | |
0c061b57 | 289 | */ |
65d87fe6 | 290 | kdebug("gc sync"); |
0c061b57 | 291 | synchronize_rcu(); |
8bc16dea DH |
292 | } |
293 | ||
65d87fe6 DH |
294 | if (!list_empty(&graveyard)) { |
295 | kdebug("gc keys"); | |
296 | key_gc_unused_keys(&graveyard); | |
297 | } | |
298 | ||
0c061b57 DH |
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. | |
304 | */ | |
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; | |
310 | } | |
311 | } | |
8bc16dea | 312 | |
0c061b57 DH |
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); | |
318 | } | |
8bc16dea | 319 | |
0c061b57 | 320 | if (gc_state & KEY_GC_REAP_AGAIN) |
3b07e9ca | 321 | schedule_work(&key_gc_work); |
0c061b57 DH |
322 | kleave(" [end %x]", gc_state); |
323 | return; | |
8bc16dea | 324 | |
0c061b57 DH |
325 | /* We found an unreferenced key - once we've removed it from the tree, |
326 | * we can safely drop the lock. | |
327 | */ | |
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); | |
8bc16dea | 332 | |
65d87fe6 | 333 | list_add_tail(&key->graveyard_link, &graveyard); |
0c061b57 DH |
334 | gc_state |= KEY_GC_REAP_AGAIN; |
335 | goto maybe_resched; | |
8bc16dea | 336 | |
2b6aa412 MM |
337 | /* We found a restricted keyring and need to update the restriction if |
338 | * it is associated with the dead key type. | |
339 | */ | |
340 | found_restricted_keyring: | |
341 | spin_unlock(&key_serial_lock); | |
342 | keyring_restriction_gc(key, key_gc_dead_keytype); | |
343 | goto maybe_resched; | |
344 | ||
0c061b57 DH |
345 | /* We found a keyring and we need to check the payload for links to |
346 | * dead or expired keys. We don't flag another reap immediately as we | |
347 | * have to wait for the old payload to be destroyed by RCU before we | |
348 | * can reap the keys to which it refers. | |
349 | */ | |
350 | found_keyring: | |
351 | spin_unlock(&key_serial_lock); | |
62fe3182 | 352 | keyring_gc(key, limit); |
0c061b57 DH |
353 | goto maybe_resched; |
354 | ||
355 | /* We found a dead key that is still referenced. Reset its type and | |
356 | * destroy its payload with its semaphore held. | |
357 | */ | |
358 | destroy_dead_key: | |
359 | spin_unlock(&key_serial_lock); | |
360 | kdebug("destroy key %d", key->serial); | |
361 | down_write(&key->sem); | |
362 | key->type = &key_type_dead; | |
363 | if (key_gc_dead_keytype->destroy) | |
364 | key_gc_dead_keytype->destroy(key); | |
365 | memset(&key->payload, KEY_DESTROY, sizeof(key->payload)); | |
366 | up_write(&key->sem); | |
367 | goto maybe_resched; | |
8bc16dea | 368 | } |