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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright 2019 Google LLC
4 */
5
6/**
7 * DOC: The Keyslot Manager
8 *
9 * Many devices with inline encryption support have a limited number of "slots"
10 * into which encryption contexts may be programmed, and requests can be tagged
11 * with a slot number to specify the key to use for en/decryption.
12 *
13 * As the number of slots is limited, and programming keys is expensive on
14 * many inline encryption hardware, we don't want to program the same key into
15 * multiple slots - if multiple requests are using the same key, we want to
16 * program just one slot with that key and use that slot for all requests.
17 *
18 * The keyslot manager manages these keyslots appropriately, and also acts as
19 * an abstraction between the inline encryption hardware and the upper layers.
20 *
21 * Lower layer devices will set up a keyslot manager in their request queue
22 * and tell it how to perform device specific operations like programming/
23 * evicting keys from keyslots.
24 *
25 * Upper layers will call blk_ksm_get_slot_for_key() to program a
26 * key into some slot in the inline encryption hardware.
27 */
28
29#define pr_fmt(fmt) "blk-crypto: " fmt
30
31#include <linux/keyslot-manager.h>
32#include <linux/device.h>
33#include <linux/atomic.h>
34#include <linux/mutex.h>
35#include <linux/pm_runtime.h>
36#include <linux/wait.h>
37#include <linux/blkdev.h>
38
39struct blk_ksm_keyslot {
40 atomic_t slot_refs;
41 struct list_head idle_slot_node;
42 struct hlist_node hash_node;
43 const struct blk_crypto_key *key;
44 struct blk_keyslot_manager *ksm;
45};
46
47static inline void blk_ksm_hw_enter(struct blk_keyslot_manager *ksm)
48{
49 /*
50 * Calling into the driver requires ksm->lock held and the device
51 * resumed. But we must resume the device first, since that can acquire
52 * and release ksm->lock via blk_ksm_reprogram_all_keys().
53 */
54 if (ksm->dev)
55 pm_runtime_get_sync(ksm->dev);
56 down_write(&ksm->lock);
57}
58
59static inline void blk_ksm_hw_exit(struct blk_keyslot_manager *ksm)
60{
61 up_write(&ksm->lock);
62 if (ksm->dev)
63 pm_runtime_put_sync(ksm->dev);
64}
65
66static inline bool blk_ksm_is_passthrough(struct blk_keyslot_manager *ksm)
67{
68 return ksm->num_slots == 0;
69}
70
71/**
72 * blk_ksm_init() - Initialize a keyslot manager
73 * @ksm: The keyslot_manager to initialize.
74 * @num_slots: The number of key slots to manage.
75 *
76 * Allocate memory for keyslots and initialize a keyslot manager. Called by
77 * e.g. storage drivers to set up a keyslot manager in their request_queue.
78 *
79 * Return: 0 on success, or else a negative error code.
80 */
81int blk_ksm_init(struct blk_keyslot_manager *ksm, unsigned int num_slots)
82{
83 unsigned int slot;
84 unsigned int i;
85 unsigned int slot_hashtable_size;
86
87 memset(ksm, 0, sizeof(*ksm));
88
89 if (num_slots == 0)
90 return -EINVAL;
91
92 ksm->slots = kvcalloc(num_slots, sizeof(ksm->slots[0]), GFP_KERNEL);
93 if (!ksm->slots)
94 return -ENOMEM;
95
96 ksm->num_slots = num_slots;
97
98 init_rwsem(&ksm->lock);
99
100 init_waitqueue_head(&ksm->idle_slots_wait_queue);
101 INIT_LIST_HEAD(&ksm->idle_slots);
102
103 for (slot = 0; slot < num_slots; slot++) {
104 ksm->slots[slot].ksm = ksm;
105 list_add_tail(&ksm->slots[slot].idle_slot_node,
106 &ksm->idle_slots);
107 }
108
109 spin_lock_init(&ksm->idle_slots_lock);
110
111 slot_hashtable_size = roundup_pow_of_two(num_slots);
112 /*
113 * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
114 * buckets. This only makes a difference when there is only 1 keyslot.
115 */
116 if (slot_hashtable_size < 2)
117 slot_hashtable_size = 2;
118
119 ksm->log_slot_ht_size = ilog2(slot_hashtable_size);
120 ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size,
121 sizeof(ksm->slot_hashtable[0]),
122 GFP_KERNEL);
123 if (!ksm->slot_hashtable)
124 goto err_destroy_ksm;
125 for (i = 0; i < slot_hashtable_size; i++)
126 INIT_HLIST_HEAD(&ksm->slot_hashtable[i]);
127
128 return 0;
129
130err_destroy_ksm:
131 blk_ksm_destroy(ksm);
132 return -ENOMEM;
133}
134EXPORT_SYMBOL_GPL(blk_ksm_init);
135
136static void blk_ksm_destroy_callback(void *ksm)
137{
138 blk_ksm_destroy(ksm);
139}
140
141/**
142 * devm_blk_ksm_init() - Resource-managed blk_ksm_init()
143 * @dev: The device which owns the blk_keyslot_manager.
144 * @ksm: The blk_keyslot_manager to initialize.
145 * @num_slots: The number of key slots to manage.
146 *
147 * Like blk_ksm_init(), but causes blk_ksm_destroy() to be called automatically
148 * on driver detach.
149 *
150 * Return: 0 on success, or else a negative error code.
151 */
152int devm_blk_ksm_init(struct device *dev, struct blk_keyslot_manager *ksm,
153 unsigned int num_slots)
154{
155 int err = blk_ksm_init(ksm, num_slots);
156
157 if (err)
158 return err;
159
160 return devm_add_action_or_reset(dev, blk_ksm_destroy_callback, ksm);
161}
162EXPORT_SYMBOL_GPL(devm_blk_ksm_init);
163
164static inline struct hlist_head *
165blk_ksm_hash_bucket_for_key(struct blk_keyslot_manager *ksm,
166 const struct blk_crypto_key *key)
167{
168 return &ksm->slot_hashtable[hash_ptr(key, ksm->log_slot_ht_size)];
169}
170
171static void blk_ksm_remove_slot_from_lru_list(struct blk_ksm_keyslot *slot)
172{
173 struct blk_keyslot_manager *ksm = slot->ksm;
174 unsigned long flags;
175
176 spin_lock_irqsave(&ksm->idle_slots_lock, flags);
177 list_del(&slot->idle_slot_node);
178 spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
179}
180
181static struct blk_ksm_keyslot *blk_ksm_find_keyslot(
182 struct blk_keyslot_manager *ksm,
183 const struct blk_crypto_key *key)
184{
185 const struct hlist_head *head = blk_ksm_hash_bucket_for_key(ksm, key);
186 struct blk_ksm_keyslot *slotp;
187
188 hlist_for_each_entry(slotp, head, hash_node) {
189 if (slotp->key == key)
190 return slotp;
191 }
192 return NULL;
193}
194
195static struct blk_ksm_keyslot *blk_ksm_find_and_grab_keyslot(
196 struct blk_keyslot_manager *ksm,
197 const struct blk_crypto_key *key)
198{
199 struct blk_ksm_keyslot *slot;
200
201 slot = blk_ksm_find_keyslot(ksm, key);
202 if (!slot)
203 return NULL;
204 if (atomic_inc_return(&slot->slot_refs) == 1) {
205 /* Took first reference to this slot; remove it from LRU list */
206 blk_ksm_remove_slot_from_lru_list(slot);
207 }
208 return slot;
209}
210
211unsigned int blk_ksm_get_slot_idx(struct blk_ksm_keyslot *slot)
212{
213 return slot - slot->ksm->slots;
214}
215EXPORT_SYMBOL_GPL(blk_ksm_get_slot_idx);
216
217/**
218 * blk_ksm_get_slot_for_key() - Program a key into a keyslot.
219 * @ksm: The keyslot manager to program the key into.
220 * @key: Pointer to the key object to program, including the raw key, crypto
221 * mode, and data unit size.
222 * @slot_ptr: A pointer to return the pointer of the allocated keyslot.
223 *
224 * Get a keyslot that's been programmed with the specified key. If one already
225 * exists, return it with incremented refcount. Otherwise, wait for a keyslot
226 * to become idle and program it.
227 *
228 * Context: Process context. Takes and releases ksm->lock.
229 * Return: BLK_STS_OK on success (and keyslot is set to the pointer of the
230 * allocated keyslot), or some other blk_status_t otherwise (and
231 * keyslot is set to NULL).
232 */
233blk_status_t blk_ksm_get_slot_for_key(struct blk_keyslot_manager *ksm,
234 const struct blk_crypto_key *key,
235 struct blk_ksm_keyslot **slot_ptr)
236{
237 struct blk_ksm_keyslot *slot;
238 int slot_idx;
239 int err;
240
241 *slot_ptr = NULL;
242
243 if (blk_ksm_is_passthrough(ksm))
244 return BLK_STS_OK;
245
246 down_read(&ksm->lock);
247 slot = blk_ksm_find_and_grab_keyslot(ksm, key);
248 up_read(&ksm->lock);
249 if (slot)
250 goto success;
251
252 for (;;) {
253 blk_ksm_hw_enter(ksm);
254 slot = blk_ksm_find_and_grab_keyslot(ksm, key);
255 if (slot) {
256 blk_ksm_hw_exit(ksm);
257 goto success;
258 }
259
260 /*
261 * If we're here, that means there wasn't a slot that was
262 * already programmed with the key. So try to program it.
263 */
264 if (!list_empty(&ksm->idle_slots))
265 break;
266
267 blk_ksm_hw_exit(ksm);
268 wait_event(ksm->idle_slots_wait_queue,
269 !list_empty(&ksm->idle_slots));
270 }
271
272 slot = list_first_entry(&ksm->idle_slots, struct blk_ksm_keyslot,
273 idle_slot_node);
274 slot_idx = blk_ksm_get_slot_idx(slot);
275
276 err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot_idx);
277 if (err) {
278 wake_up(&ksm->idle_slots_wait_queue);
279 blk_ksm_hw_exit(ksm);
280 return errno_to_blk_status(err);
281 }
282
283 /* Move this slot to the hash list for the new key. */
284 if (slot->key)
285 hlist_del(&slot->hash_node);
286 slot->key = key;
287 hlist_add_head(&slot->hash_node, blk_ksm_hash_bucket_for_key(ksm, key));
288
289 atomic_set(&slot->slot_refs, 1);
290
291 blk_ksm_remove_slot_from_lru_list(slot);
292
293 blk_ksm_hw_exit(ksm);
294success:
295 *slot_ptr = slot;
296 return BLK_STS_OK;
297}
298
299/**
300 * blk_ksm_put_slot() - Release a reference to a slot
301 * @slot: The keyslot to release the reference of.
302 *
303 * Context: Any context.
304 */
305void blk_ksm_put_slot(struct blk_ksm_keyslot *slot)
306{
307 struct blk_keyslot_manager *ksm;
308 unsigned long flags;
309
310 if (!slot)
311 return;
312
313 ksm = slot->ksm;
314
315 if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
316 &ksm->idle_slots_lock, flags)) {
317 list_add_tail(&slot->idle_slot_node, &ksm->idle_slots);
318 spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
319 wake_up(&ksm->idle_slots_wait_queue);
320 }
321}
322
323/**
324 * blk_ksm_crypto_cfg_supported() - Find out if a crypto configuration is
325 * supported by a ksm.
326 * @ksm: The keyslot manager to check
327 * @cfg: The crypto configuration to check for.
328 *
329 * Checks for crypto_mode/data unit size/dun bytes support.
330 *
331 * Return: Whether or not this ksm supports the specified crypto config.
332 */
333bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
334 const struct blk_crypto_config *cfg)
335{
336 if (!ksm)
337 return false;
338 if (!(ksm->crypto_modes_supported[cfg->crypto_mode] &
339 cfg->data_unit_size))
340 return false;
341 if (ksm->max_dun_bytes_supported < cfg->dun_bytes)
342 return false;
343 return true;
344}
345
346/**
347 * blk_ksm_evict_key() - Evict a key from the lower layer device.
348 * @ksm: The keyslot manager to evict from
349 * @key: The key to evict
350 *
351 * Find the keyslot that the specified key was programmed into, and evict that
352 * slot from the lower layer device. The slot must not be in use by any
353 * in-flight IO when this function is called.
354 *
355 * Context: Process context. Takes and releases ksm->lock.
356 * Return: 0 on success or if there's no keyslot with the specified key, -EBUSY
357 * if the keyslot is still in use, or another -errno value on other
358 * error.
359 */
360int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
361 const struct blk_crypto_key *key)
362{
363 struct blk_ksm_keyslot *slot;
364 int err = 0;
365
366 if (blk_ksm_is_passthrough(ksm)) {
367 if (ksm->ksm_ll_ops.keyslot_evict) {
368 blk_ksm_hw_enter(ksm);
369 err = ksm->ksm_ll_ops.keyslot_evict(ksm, key, -1);
370 blk_ksm_hw_exit(ksm);
371 return err;
372 }
373 return 0;
374 }
375
376 blk_ksm_hw_enter(ksm);
377 slot = blk_ksm_find_keyslot(ksm, key);
378 if (!slot)
379 goto out_unlock;
380
381 if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
382 err = -EBUSY;
383 goto out_unlock;
384 }
385 err = ksm->ksm_ll_ops.keyslot_evict(ksm, key,
386 blk_ksm_get_slot_idx(slot));
387 if (err)
388 goto out_unlock;
389
390 hlist_del(&slot->hash_node);
391 slot->key = NULL;
392 err = 0;
393out_unlock:
394 blk_ksm_hw_exit(ksm);
395 return err;
396}
397
398/**
399 * blk_ksm_reprogram_all_keys() - Re-program all keyslots.
400 * @ksm: The keyslot manager
401 *
402 * Re-program all keyslots that are supposed to have a key programmed. This is
403 * intended only for use by drivers for hardware that loses its keys on reset.
404 *
405 * Context: Process context. Takes and releases ksm->lock.
406 */
407void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm)
408{
409 unsigned int slot;
410
411 if (blk_ksm_is_passthrough(ksm))
412 return;
413
414 /* This is for device initialization, so don't resume the device */
415 down_write(&ksm->lock);
416 for (slot = 0; slot < ksm->num_slots; slot++) {
417 const struct blk_crypto_key *key = ksm->slots[slot].key;
418 int err;
419
420 if (!key)
421 continue;
422
423 err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot);
424 WARN_ON(err);
425 }
426 up_write(&ksm->lock);
427}
428EXPORT_SYMBOL_GPL(blk_ksm_reprogram_all_keys);
429
430void blk_ksm_destroy(struct blk_keyslot_manager *ksm)
431{
432 if (!ksm)
433 return;
434 kvfree(ksm->slot_hashtable);
435 kvfree_sensitive(ksm->slots, sizeof(ksm->slots[0]) * ksm->num_slots);
436 memzero_explicit(ksm, sizeof(*ksm));
437}
438EXPORT_SYMBOL_GPL(blk_ksm_destroy);
439
440bool blk_ksm_register(struct blk_keyslot_manager *ksm, struct request_queue *q)
441{
442 if (blk_integrity_queue_supports_integrity(q)) {
443 pr_warn("Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n");
444 return false;
445 }
446 q->ksm = ksm;
447 return true;
448}
449EXPORT_SYMBOL_GPL(blk_ksm_register);
450
451void blk_ksm_unregister(struct request_queue *q)
452{
453 q->ksm = NULL;
454}
455
456/**
457 * blk_ksm_intersect_modes() - restrict supported modes by child device
458 * @parent: The keyslot manager for parent device
459 * @child: The keyslot manager for child device, or NULL
460 *
461 * Clear any crypto mode support bits in @parent that aren't set in @child.
462 * If @child is NULL, then all parent bits are cleared.
463 *
464 * Only use this when setting up the keyslot manager for a layered device,
465 * before it's been exposed yet.
466 */
467void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
468 const struct blk_keyslot_manager *child)
469{
470 if (child) {
471 unsigned int i;
472
473 parent->max_dun_bytes_supported =
474 min(parent->max_dun_bytes_supported,
475 child->max_dun_bytes_supported);
476 for (i = 0; i < ARRAY_SIZE(child->crypto_modes_supported);
477 i++) {
478 parent->crypto_modes_supported[i] &=
479 child->crypto_modes_supported[i];
480 }
481 } else {
482 parent->max_dun_bytes_supported = 0;
483 memset(parent->crypto_modes_supported, 0,
484 sizeof(parent->crypto_modes_supported));
485 }
486}
487EXPORT_SYMBOL_GPL(blk_ksm_intersect_modes);
488
489/**
490 * blk_ksm_is_superset() - Check if a KSM supports a superset of crypto modes
491 * and DUN bytes that another KSM supports. Here,
492 * "superset" refers to the mathematical meaning of the
493 * word - i.e. if two KSMs have the *same* capabilities,
494 * they *are* considered supersets of each other.
495 * @ksm_superset: The KSM that we want to verify is a superset
496 * @ksm_subset: The KSM that we want to verify is a subset
497 *
498 * Return: True if @ksm_superset supports a superset of the crypto modes and DUN
499 * bytes that @ksm_subset supports.
500 */
501bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
502 struct blk_keyslot_manager *ksm_subset)
503{
504 int i;
505
506 if (!ksm_subset)
507 return true;
508
509 if (!ksm_superset)
510 return false;
511
512 for (i = 0; i < ARRAY_SIZE(ksm_superset->crypto_modes_supported); i++) {
513 if (ksm_subset->crypto_modes_supported[i] &
514 (~ksm_superset->crypto_modes_supported[i])) {
515 return false;
516 }
517 }
518
519 if (ksm_subset->max_dun_bytes_supported >
520 ksm_superset->max_dun_bytes_supported) {
521 return false;
522 }
523
524 return true;
525}
526EXPORT_SYMBOL_GPL(blk_ksm_is_superset);
527
528/**
529 * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
530 * another KSM
531 * @target_ksm: The KSM whose restrictions to update.
532 * @reference_ksm: The KSM to whose restrictions this function will update
533 * @target_ksm's restrictions to.
534 *
535 * Blk-crypto requires that crypto capabilities that were
536 * advertised when a bio was created continue to be supported by the
537 * device until that bio is ended. This is turn means that a device cannot
538 * shrink its advertised crypto capabilities without any explicit
539 * synchronization with upper layers. So if there's no such explicit
540 * synchronization, @reference_ksm must support all the crypto capabilities that
541 * @target_ksm does
542 * (i.e. we need blk_ksm_is_superset(@reference_ksm, @target_ksm) == true).
543 *
544 * Note also that as long as the crypto capabilities are being expanded, the
545 * order of updates becoming visible is not important because it's alright
546 * for blk-crypto to see stale values - they only cause blk-crypto to
547 * believe that a crypto capability isn't supported when it actually is (which
548 * might result in blk-crypto-fallback being used if available, or the bio being
549 * failed).
550 */
551void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
552 struct blk_keyslot_manager *reference_ksm)
553{
554 memcpy(target_ksm->crypto_modes_supported,
555 reference_ksm->crypto_modes_supported,
556 sizeof(target_ksm->crypto_modes_supported));
557
558 target_ksm->max_dun_bytes_supported =
559 reference_ksm->max_dun_bytes_supported;
560}
561EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
562
563/**
564 * blk_ksm_init_passthrough() - Init a passthrough keyslot manager
565 * @ksm: The keyslot manager to init
566 *
567 * Initialize a passthrough keyslot manager.
568 * Called by e.g. storage drivers to set up a keyslot manager in their
569 * request_queue, when the storage driver wants to manage its keys by itself.
570 * This is useful for inline encryption hardware that doesn't have the concept
571 * of keyslots, and for layered devices.
572 */
573void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm)
574{
575 memset(ksm, 0, sizeof(*ksm));
576 init_rwsem(&ksm->lock);
577}
578EXPORT_SYMBOL_GPL(blk_ksm_init_passthrough);