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b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
5d135440 DH |
2 | /* Key garbage collector |
3 | * | |
0c061b57 | 4 | * Copyright (C) 2009-2011 Red Hat, Inc. All Rights Reserved. |
5d135440 | 5 | * Written by David Howells (dhowells@redhat.com) |
5d135440 DH |
6 | */ |
7 | ||
8bc16dea DH |
8 | #include <linux/slab.h> |
9 | #include <linux/security.h> | |
5d135440 DH |
10 | #include <keys/keyring-type.h> |
11 | #include "internal.h" | |
12 | ||
13 | /* | |
14 | * Delay between key revocation/expiry in seconds | |
15 | */ | |
16 | unsigned key_gc_delay = 5 * 60; | |
17 | ||
18 | /* | |
8bc16dea DH |
19 | * Reaper for unused keys. |
20 | */ | |
0c061b57 DH |
21 | static void key_garbage_collector(struct work_struct *work); |
22 | DECLARE_WORK(key_gc_work, key_garbage_collector); | |
8bc16dea DH |
23 | |
24 | /* | |
25 | * Reaper for links from keyrings to dead keys. | |
5d135440 | 26 | */ |
24ed960a | 27 | static void key_gc_timer_func(struct timer_list *); |
1d27e3e2 | 28 | static DEFINE_TIMER(key_gc_timer, key_gc_timer_func); |
0c061b57 | 29 | |
074d5898 | 30 | static time64_t key_gc_next_run = TIME64_MAX; |
0c061b57 DH |
31 | static struct key_type *key_gc_dead_keytype; |
32 | ||
33 | static unsigned long key_gc_flags; | |
34 | #define KEY_GC_KEY_EXPIRED 0 /* A key expired and needs unlinking */ | |
35 | #define KEY_GC_REAP_KEYTYPE 1 /* A keytype is being unregistered */ | |
36 | #define KEY_GC_REAPING_KEYTYPE 2 /* Cleared when keytype reaped */ | |
37 | ||
38 | ||
39 | /* | |
40 | * Any key whose type gets unregistered will be re-typed to this if it can't be | |
41 | * immediately unlinked. | |
42 | */ | |
43 | struct key_type key_type_dead = { | |
c1644fe0 | 44 | .name = ".dead", |
0c061b57 | 45 | }; |
5d135440 DH |
46 | |
47 | /* | |
973c9f4f DH |
48 | * Schedule a garbage collection run. |
49 | * - time precision isn't particularly important | |
5d135440 | 50 | */ |
074d5898 | 51 | void key_schedule_gc(time64_t gc_at) |
5d135440 DH |
52 | { |
53 | unsigned long expires; | |
074d5898 | 54 | time64_t now = ktime_get_real_seconds(); |
5d135440 | 55 | |
074d5898 | 56 | kenter("%lld", gc_at - now); |
5d135440 | 57 | |
0c061b57 DH |
58 | if (gc_at <= now || test_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) { |
59 | kdebug("IMMEDIATE"); | |
3b07e9ca | 60 | schedule_work(&key_gc_work); |
5d135440 | 61 | } else if (gc_at < key_gc_next_run) { |
0c061b57 DH |
62 | kdebug("DEFERRED"); |
63 | key_gc_next_run = gc_at; | |
5d135440 DH |
64 | expires = jiffies + (gc_at - now) * HZ; |
65 | mod_timer(&key_gc_timer, expires); | |
66 | } | |
67 | } | |
68 | ||
fd75815f DH |
69 | /* |
70 | * Schedule a dead links collection run. | |
71 | */ | |
72 | void key_schedule_gc_links(void) | |
73 | { | |
74 | set_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags); | |
3b07e9ca | 75 | schedule_work(&key_gc_work); |
fd75815f DH |
76 | } |
77 | ||
5d135440 | 78 | /* |
0c061b57 DH |
79 | * Some key's cleanup time was met after it expired, so we need to get the |
80 | * reaper to go through a cycle finding expired keys. | |
5d135440 | 81 | */ |
24ed960a | 82 | static void key_gc_timer_func(struct timer_list *unused) |
5d135440 DH |
83 | { |
84 | kenter(""); | |
074d5898 | 85 | key_gc_next_run = TIME64_MAX; |
fd75815f | 86 | key_schedule_gc_links(); |
5d135440 DH |
87 | } |
88 | ||
0c061b57 DH |
89 | /* |
90 | * Reap keys of dead type. | |
91 | * | |
92 | * We use three flags to make sure we see three complete cycles of the garbage | |
93 | * collector: the first to mark keys of that type as being dead, the second to | |
94 | * collect dead links and the third to clean up the dead keys. We have to be | |
95 | * careful as there may already be a cycle in progress. | |
96 | * | |
97 | * The caller must be holding key_types_sem. | |
98 | */ | |
99 | void key_gc_keytype(struct key_type *ktype) | |
100 | { | |
101 | kenter("%s", ktype->name); | |
102 | ||
103 | key_gc_dead_keytype = ktype; | |
104 | set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); | |
105 | smp_mb(); | |
106 | set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags); | |
107 | ||
108 | kdebug("schedule"); | |
3b07e9ca | 109 | schedule_work(&key_gc_work); |
0c061b57 DH |
110 | |
111 | kdebug("sleep"); | |
74316201 | 112 | wait_on_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE, |
0c061b57 DH |
113 | TASK_UNINTERRUPTIBLE); |
114 | ||
115 | key_gc_dead_keytype = NULL; | |
116 | kleave(""); | |
117 | } | |
118 | ||
5d135440 | 119 | /* |
65d87fe6 | 120 | * Garbage collect a list of unreferenced, detached keys |
5d135440 | 121 | */ |
65d87fe6 | 122 | static noinline void key_gc_unused_keys(struct list_head *keys) |
5d135440 | 123 | { |
65d87fe6 DH |
124 | while (!list_empty(keys)) { |
125 | struct key *key = | |
126 | list_entry(keys->next, struct key, graveyard_link); | |
363b02da DH |
127 | short state = key->state; |
128 | ||
65d87fe6 DH |
129 | list_del(&key->graveyard_link); |
130 | ||
131 | kdebug("- %u", key->serial); | |
132 | key_check(key); | |
133 | ||
f05819df | 134 | /* Throw away the key data if the key is instantiated */ |
363b02da | 135 | if (state == KEY_IS_POSITIVE && key->type->destroy) |
94c4554b DH |
136 | key->type->destroy(key); |
137 | ||
65d87fe6 DH |
138 | security_key_free(key); |
139 | ||
140 | /* deal with the user's key tracking and quota */ | |
141 | if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) { | |
142 | spin_lock(&key->user->lock); | |
143 | key->user->qnkeys--; | |
144 | key->user->qnbytes -= key->quotalen; | |
145 | spin_unlock(&key->user->lock); | |
146 | } | |
5d135440 | 147 | |
65d87fe6 | 148 | atomic_dec(&key->user->nkeys); |
363b02da | 149 | if (state != KEY_IS_UNINSTANTIATED) |
65d87fe6 | 150 | atomic_dec(&key->user->nikeys); |
5d135440 | 151 | |
a3a87844 | 152 | key_user_put(key->user); |
3b6e4de0 | 153 | key_put_tag(key->domain_tag); |
65d87fe6 | 154 | kfree(key->description); |
5d135440 | 155 | |
0620fddb | 156 | memzero_explicit(key, sizeof(*key)); |
65d87fe6 DH |
157 | kmem_cache_free(key_jar, key); |
158 | } | |
5d135440 | 159 | } |
8bc16dea DH |
160 | |
161 | /* | |
162 | * Garbage collector for unused keys. | |
163 | * | |
164 | * This is done in process context so that we don't have to disable interrupts | |
165 | * all over the place. key_put() schedules this rather than trying to do the | |
166 | * cleanup itself, which means key_put() doesn't have to sleep. | |
167 | */ | |
0c061b57 | 168 | static void key_garbage_collector(struct work_struct *work) |
8bc16dea | 169 | { |
65d87fe6 | 170 | static LIST_HEAD(graveyard); |
0c061b57 DH |
171 | static u8 gc_state; /* Internal persistent state */ |
172 | #define KEY_GC_REAP_AGAIN 0x01 /* - Need another cycle */ | |
173 | #define KEY_GC_REAPING_LINKS 0x02 /* - We need to reap links */ | |
174 | #define KEY_GC_SET_TIMER 0x04 /* - We need to restart the timer */ | |
175 | #define KEY_GC_REAPING_DEAD_1 0x10 /* - We need to mark dead keys */ | |
176 | #define KEY_GC_REAPING_DEAD_2 0x20 /* - We need to reap dead key links */ | |
177 | #define KEY_GC_REAPING_DEAD_3 0x40 /* - We need to reap dead keys */ | |
178 | #define KEY_GC_FOUND_DEAD_KEY 0x80 /* - We found at least one dead key */ | |
179 | ||
180 | struct rb_node *cursor; | |
8bc16dea | 181 | struct key *key; |
074d5898 | 182 | time64_t new_timer, limit; |
0c061b57 DH |
183 | |
184 | kenter("[%lx,%x]", key_gc_flags, gc_state); | |
185 | ||
074d5898 | 186 | limit = ktime_get_real_seconds(); |
0c061b57 DH |
187 | if (limit > key_gc_delay) |
188 | limit -= key_gc_delay; | |
189 | else | |
190 | limit = key_gc_delay; | |
191 | ||
192 | /* Work out what we're going to be doing in this pass */ | |
193 | gc_state &= KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2; | |
194 | gc_state <<= 1; | |
195 | if (test_and_clear_bit(KEY_GC_KEY_EXPIRED, &key_gc_flags)) | |
196 | gc_state |= KEY_GC_REAPING_LINKS | KEY_GC_SET_TIMER; | |
197 | ||
198 | if (test_and_clear_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags)) | |
199 | gc_state |= KEY_GC_REAPING_DEAD_1; | |
200 | kdebug("new pass %x", gc_state); | |
201 | ||
074d5898 | 202 | new_timer = TIME64_MAX; |
8bc16dea | 203 | |
0c061b57 DH |
204 | /* As only this function is permitted to remove things from the key |
205 | * serial tree, if cursor is non-NULL then it will always point to a | |
206 | * valid node in the tree - even if lock got dropped. | |
207 | */ | |
8bc16dea | 208 | spin_lock(&key_serial_lock); |
0c061b57 | 209 | cursor = rb_first(&key_serial_tree); |
8bc16dea | 210 | |
0c061b57 DH |
211 | continue_scanning: |
212 | while (cursor) { | |
213 | key = rb_entry(cursor, struct key, serial_node); | |
214 | cursor = rb_next(cursor); | |
8bc16dea | 215 | |
fff29291 | 216 | if (refcount_read(&key->usage) == 0) |
0c061b57 DH |
217 | goto found_unreferenced_key; |
218 | ||
219 | if (unlikely(gc_state & KEY_GC_REAPING_DEAD_1)) { | |
220 | if (key->type == key_gc_dead_keytype) { | |
221 | gc_state |= KEY_GC_FOUND_DEAD_KEY; | |
222 | set_bit(KEY_FLAG_DEAD, &key->flags); | |
028db3e2 | 223 | key->perm = 0; |
0c061b57 | 224 | goto skip_dead_key; |
2b6aa412 MM |
225 | } else if (key->type == &key_type_keyring && |
226 | key->restrict_link) { | |
227 | goto found_restricted_keyring; | |
0c061b57 DH |
228 | } |
229 | } | |
230 | ||
231 | if (gc_state & KEY_GC_SET_TIMER) { | |
232 | if (key->expiry > limit && key->expiry < new_timer) { | |
074d5898 | 233 | kdebug("will expire %x in %lld", |
0c061b57 DH |
234 | key_serial(key), key->expiry - limit); |
235 | new_timer = key->expiry; | |
236 | } | |
237 | } | |
238 | ||
239 | if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) | |
240 | if (key->type == key_gc_dead_keytype) | |
241 | gc_state |= KEY_GC_FOUND_DEAD_KEY; | |
242 | ||
243 | if ((gc_state & KEY_GC_REAPING_LINKS) || | |
244 | unlikely(gc_state & KEY_GC_REAPING_DEAD_2)) { | |
245 | if (key->type == &key_type_keyring) | |
246 | goto found_keyring; | |
247 | } | |
248 | ||
249 | if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) | |
250 | if (key->type == key_gc_dead_keytype) | |
251 | goto destroy_dead_key; | |
252 | ||
253 | skip_dead_key: | |
254 | if (spin_is_contended(&key_serial_lock) || need_resched()) | |
255 | goto contended; | |
8bc16dea DH |
256 | } |
257 | ||
0c061b57 | 258 | contended: |
8bc16dea | 259 | spin_unlock(&key_serial_lock); |
8bc16dea | 260 | |
0c061b57 DH |
261 | maybe_resched: |
262 | if (cursor) { | |
263 | cond_resched(); | |
264 | spin_lock(&key_serial_lock); | |
265 | goto continue_scanning; | |
266 | } | |
8bc16dea | 267 | |
0c061b57 DH |
268 | /* We've completed the pass. Set the timer if we need to and queue a |
269 | * new cycle if necessary. We keep executing cycles until we find one | |
270 | * where we didn't reap any keys. | |
271 | */ | |
272 | kdebug("pass complete"); | |
8bc16dea | 273 | |
074d5898 | 274 | if (gc_state & KEY_GC_SET_TIMER && new_timer != (time64_t)TIME64_MAX) { |
0c061b57 DH |
275 | new_timer += key_gc_delay; |
276 | key_schedule_gc(new_timer); | |
277 | } | |
8bc16dea | 278 | |
65d87fe6 DH |
279 | if (unlikely(gc_state & KEY_GC_REAPING_DEAD_2) || |
280 | !list_empty(&graveyard)) { | |
281 | /* Make sure that all pending keyring payload destructions are | |
282 | * fulfilled and that people aren't now looking at dead or | |
283 | * dying keys that they don't have a reference upon or a link | |
284 | * to. | |
0c061b57 | 285 | */ |
65d87fe6 | 286 | kdebug("gc sync"); |
0c061b57 | 287 | synchronize_rcu(); |
8bc16dea DH |
288 | } |
289 | ||
65d87fe6 DH |
290 | if (!list_empty(&graveyard)) { |
291 | kdebug("gc keys"); | |
292 | key_gc_unused_keys(&graveyard); | |
293 | } | |
294 | ||
0c061b57 DH |
295 | if (unlikely(gc_state & (KEY_GC_REAPING_DEAD_1 | |
296 | KEY_GC_REAPING_DEAD_2))) { | |
297 | if (!(gc_state & KEY_GC_FOUND_DEAD_KEY)) { | |
298 | /* No remaining dead keys: short circuit the remaining | |
299 | * keytype reap cycles. | |
300 | */ | |
301 | kdebug("dead short"); | |
302 | gc_state &= ~(KEY_GC_REAPING_DEAD_1 | KEY_GC_REAPING_DEAD_2); | |
303 | gc_state |= KEY_GC_REAPING_DEAD_3; | |
304 | } else { | |
305 | gc_state |= KEY_GC_REAP_AGAIN; | |
306 | } | |
307 | } | |
8bc16dea | 308 | |
0c061b57 DH |
309 | if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) { |
310 | kdebug("dead wake"); | |
311 | smp_mb(); | |
312 | clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags); | |
313 | wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE); | |
314 | } | |
8bc16dea | 315 | |
0c061b57 | 316 | if (gc_state & KEY_GC_REAP_AGAIN) |
3b07e9ca | 317 | schedule_work(&key_gc_work); |
0c061b57 DH |
318 | kleave(" [end %x]", gc_state); |
319 | return; | |
8bc16dea | 320 | |
0c061b57 DH |
321 | /* We found an unreferenced key - once we've removed it from the tree, |
322 | * we can safely drop the lock. | |
323 | */ | |
324 | found_unreferenced_key: | |
325 | kdebug("unrefd key %d", key->serial); | |
326 | rb_erase(&key->serial_node, &key_serial_tree); | |
327 | spin_unlock(&key_serial_lock); | |
8bc16dea | 328 | |
65d87fe6 | 329 | list_add_tail(&key->graveyard_link, &graveyard); |
0c061b57 DH |
330 | gc_state |= KEY_GC_REAP_AGAIN; |
331 | goto maybe_resched; | |
8bc16dea | 332 | |
2b6aa412 MM |
333 | /* We found a restricted keyring and need to update the restriction if |
334 | * it is associated with the dead key type. | |
335 | */ | |
336 | found_restricted_keyring: | |
337 | spin_unlock(&key_serial_lock); | |
338 | keyring_restriction_gc(key, key_gc_dead_keytype); | |
339 | goto maybe_resched; | |
340 | ||
0c061b57 DH |
341 | /* We found a keyring and we need to check the payload for links to |
342 | * dead or expired keys. We don't flag another reap immediately as we | |
343 | * have to wait for the old payload to be destroyed by RCU before we | |
344 | * can reap the keys to which it refers. | |
345 | */ | |
346 | found_keyring: | |
347 | spin_unlock(&key_serial_lock); | |
62fe3182 | 348 | keyring_gc(key, limit); |
0c061b57 DH |
349 | goto maybe_resched; |
350 | ||
351 | /* We found a dead key that is still referenced. Reset its type and | |
352 | * destroy its payload with its semaphore held. | |
353 | */ | |
354 | destroy_dead_key: | |
355 | spin_unlock(&key_serial_lock); | |
356 | kdebug("destroy key %d", key->serial); | |
357 | down_write(&key->sem); | |
358 | key->type = &key_type_dead; | |
359 | if (key_gc_dead_keytype->destroy) | |
360 | key_gc_dead_keytype->destroy(key); | |
361 | memset(&key->payload, KEY_DESTROY, sizeof(key->payload)); | |
362 | up_write(&key->sem); | |
363 | goto maybe_resched; | |
8bc16dea | 364 | } |