xref: /openbmc/linux/block/blk-crypto-profile.c (revision 2fb48d88)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright 2019 Google LLC
4  */
5 
6 /**
7  * DOC: blk-crypto profiles
8  *
9  * 'struct blk_crypto_profile' contains all generic inline encryption-related
10  * state for a particular inline encryption device.  blk_crypto_profile serves
11  * as the way that drivers for inline encryption hardware expose their crypto
12  * capabilities and certain functions (e.g., functions to program and evict
13  * keys) to upper layers.  Device drivers that want to support inline encryption
14  * construct a crypto profile, then associate it with the disk's request_queue.
15  *
16  * If the device has keyslots, then its blk_crypto_profile also handles managing
17  * these keyslots in a device-independent way, using the driver-provided
18  * functions to program and evict keys as needed.  This includes keeping track
19  * of which key and how many I/O requests are using each keyslot, getting
20  * keyslots for I/O requests, and handling key eviction requests.
21  *
22  * For more information, see Documentation/block/inline-encryption.rst.
23  */
24 
25 #define pr_fmt(fmt) "blk-crypto: " fmt
26 
27 #include <linux/blk-crypto-profile.h>
28 #include <linux/device.h>
29 #include <linux/atomic.h>
30 #include <linux/mutex.h>
31 #include <linux/pm_runtime.h>
32 #include <linux/wait.h>
33 #include <linux/blkdev.h>
34 #include <linux/blk-integrity.h>
35 #include "blk-crypto-internal.h"
36 
37 struct blk_crypto_keyslot {
38 	atomic_t slot_refs;
39 	struct list_head idle_slot_node;
40 	struct hlist_node hash_node;
41 	const struct blk_crypto_key *key;
42 	struct blk_crypto_profile *profile;
43 };
44 
blk_crypto_hw_enter(struct blk_crypto_profile * profile)45 static inline void blk_crypto_hw_enter(struct blk_crypto_profile *profile)
46 {
47 	/*
48 	 * Calling into the driver requires profile->lock held and the device
49 	 * resumed.  But we must resume the device first, since that can acquire
50 	 * and release profile->lock via blk_crypto_reprogram_all_keys().
51 	 */
52 	if (profile->dev)
53 		pm_runtime_get_sync(profile->dev);
54 	down_write(&profile->lock);
55 }
56 
blk_crypto_hw_exit(struct blk_crypto_profile * profile)57 static inline void blk_crypto_hw_exit(struct blk_crypto_profile *profile)
58 {
59 	up_write(&profile->lock);
60 	if (profile->dev)
61 		pm_runtime_put_sync(profile->dev);
62 }
63 
64 /**
65  * blk_crypto_profile_init() - Initialize a blk_crypto_profile
66  * @profile: the blk_crypto_profile to initialize
67  * @num_slots: the number of keyslots
68  *
69  * Storage drivers must call this when starting to set up a blk_crypto_profile,
70  * before filling in additional fields.
71  *
72  * Return: 0 on success, or else a negative error code.
73  */
blk_crypto_profile_init(struct blk_crypto_profile * profile,unsigned int num_slots)74 int blk_crypto_profile_init(struct blk_crypto_profile *profile,
75 			    unsigned int num_slots)
76 {
77 	unsigned int slot;
78 	unsigned int i;
79 	unsigned int slot_hashtable_size;
80 
81 	memset(profile, 0, sizeof(*profile));
82 
83 	/*
84 	 * profile->lock of an underlying device can nest inside profile->lock
85 	 * of a device-mapper device, so use a dynamic lock class to avoid
86 	 * false-positive lockdep reports.
87 	 */
88 	lockdep_register_key(&profile->lockdep_key);
89 	__init_rwsem(&profile->lock, "&profile->lock", &profile->lockdep_key);
90 
91 	if (num_slots == 0)
92 		return 0;
93 
94 	/* Initialize keyslot management data. */
95 
96 	profile->slots = kvcalloc(num_slots, sizeof(profile->slots[0]),
97 				  GFP_KERNEL);
98 	if (!profile->slots)
99 		goto err_destroy;
100 
101 	profile->num_slots = num_slots;
102 
103 	init_waitqueue_head(&profile->idle_slots_wait_queue);
104 	INIT_LIST_HEAD(&profile->idle_slots);
105 
106 	for (slot = 0; slot < num_slots; slot++) {
107 		profile->slots[slot].profile = profile;
108 		list_add_tail(&profile->slots[slot].idle_slot_node,
109 			      &profile->idle_slots);
110 	}
111 
112 	spin_lock_init(&profile->idle_slots_lock);
113 
114 	slot_hashtable_size = roundup_pow_of_two(num_slots);
115 	/*
116 	 * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
117 	 * buckets.  This only makes a difference when there is only 1 keyslot.
118 	 */
119 	if (slot_hashtable_size < 2)
120 		slot_hashtable_size = 2;
121 
122 	profile->log_slot_ht_size = ilog2(slot_hashtable_size);
123 	profile->slot_hashtable =
124 		kvmalloc_array(slot_hashtable_size,
125 			       sizeof(profile->slot_hashtable[0]), GFP_KERNEL);
126 	if (!profile->slot_hashtable)
127 		goto err_destroy;
128 	for (i = 0; i < slot_hashtable_size; i++)
129 		INIT_HLIST_HEAD(&profile->slot_hashtable[i]);
130 
131 	return 0;
132 
133 err_destroy:
134 	blk_crypto_profile_destroy(profile);
135 	return -ENOMEM;
136 }
137 EXPORT_SYMBOL_GPL(blk_crypto_profile_init);
138 
blk_crypto_profile_destroy_callback(void * profile)139 static void blk_crypto_profile_destroy_callback(void *profile)
140 {
141 	blk_crypto_profile_destroy(profile);
142 }
143 
144 /**
145  * devm_blk_crypto_profile_init() - Resource-managed blk_crypto_profile_init()
146  * @dev: the device which owns the blk_crypto_profile
147  * @profile: the blk_crypto_profile to initialize
148  * @num_slots: the number of keyslots
149  *
150  * Like blk_crypto_profile_init(), but causes blk_crypto_profile_destroy() to be
151  * called automatically on driver detach.
152  *
153  * Return: 0 on success, or else a negative error code.
154  */
devm_blk_crypto_profile_init(struct device * dev,struct blk_crypto_profile * profile,unsigned int num_slots)155 int devm_blk_crypto_profile_init(struct device *dev,
156 				 struct blk_crypto_profile *profile,
157 				 unsigned int num_slots)
158 {
159 	int err = blk_crypto_profile_init(profile, num_slots);
160 
161 	if (err)
162 		return err;
163 
164 	return devm_add_action_or_reset(dev,
165 					blk_crypto_profile_destroy_callback,
166 					profile);
167 }
168 EXPORT_SYMBOL_GPL(devm_blk_crypto_profile_init);
169 
170 static inline struct hlist_head *
blk_crypto_hash_bucket_for_key(struct blk_crypto_profile * profile,const struct blk_crypto_key * key)171 blk_crypto_hash_bucket_for_key(struct blk_crypto_profile *profile,
172 			       const struct blk_crypto_key *key)
173 {
174 	return &profile->slot_hashtable[
175 			hash_ptr(key, profile->log_slot_ht_size)];
176 }
177 
178 static void
blk_crypto_remove_slot_from_lru_list(struct blk_crypto_keyslot * slot)179 blk_crypto_remove_slot_from_lru_list(struct blk_crypto_keyslot *slot)
180 {
181 	struct blk_crypto_profile *profile = slot->profile;
182 	unsigned long flags;
183 
184 	spin_lock_irqsave(&profile->idle_slots_lock, flags);
185 	list_del(&slot->idle_slot_node);
186 	spin_unlock_irqrestore(&profile->idle_slots_lock, flags);
187 }
188 
189 static struct blk_crypto_keyslot *
blk_crypto_find_keyslot(struct blk_crypto_profile * profile,const struct blk_crypto_key * key)190 blk_crypto_find_keyslot(struct blk_crypto_profile *profile,
191 			const struct blk_crypto_key *key)
192 {
193 	const struct hlist_head *head =
194 		blk_crypto_hash_bucket_for_key(profile, key);
195 	struct blk_crypto_keyslot *slotp;
196 
197 	hlist_for_each_entry(slotp, head, hash_node) {
198 		if (slotp->key == key)
199 			return slotp;
200 	}
201 	return NULL;
202 }
203 
204 static struct blk_crypto_keyslot *
blk_crypto_find_and_grab_keyslot(struct blk_crypto_profile * profile,const struct blk_crypto_key * key)205 blk_crypto_find_and_grab_keyslot(struct blk_crypto_profile *profile,
206 				 const struct blk_crypto_key *key)
207 {
208 	struct blk_crypto_keyslot *slot;
209 
210 	slot = blk_crypto_find_keyslot(profile, key);
211 	if (!slot)
212 		return NULL;
213 	if (atomic_inc_return(&slot->slot_refs) == 1) {
214 		/* Took first reference to this slot; remove it from LRU list */
215 		blk_crypto_remove_slot_from_lru_list(slot);
216 	}
217 	return slot;
218 }
219 
220 /**
221  * blk_crypto_keyslot_index() - Get the index of a keyslot
222  * @slot: a keyslot that blk_crypto_get_keyslot() returned
223  *
224  * Return: the 0-based index of the keyslot within the device's keyslots.
225  */
blk_crypto_keyslot_index(struct blk_crypto_keyslot * slot)226 unsigned int blk_crypto_keyslot_index(struct blk_crypto_keyslot *slot)
227 {
228 	return slot - slot->profile->slots;
229 }
230 EXPORT_SYMBOL_GPL(blk_crypto_keyslot_index);
231 
232 /**
233  * blk_crypto_get_keyslot() - Get a keyslot for a key, if needed.
234  * @profile: the crypto profile of the device the key will be used on
235  * @key: the key that will be used
236  * @slot_ptr: If a keyslot is allocated, an opaque pointer to the keyslot struct
237  *	      will be stored here.  blk_crypto_put_keyslot() must be called
238  *	      later to release it.  Otherwise, NULL will be stored here.
239  *
240  * If the device has keyslots, this gets a keyslot that's been programmed with
241  * the specified key.  If the key is already in a slot, this reuses it;
242  * otherwise this waits for a slot to become idle and programs the key into it.
243  *
244  * Context: Process context. Takes and releases profile->lock.
245  * Return: BLK_STS_OK on success, meaning that either a keyslot was allocated or
246  *	   one wasn't needed; or a blk_status_t error on failure.
247  */
blk_crypto_get_keyslot(struct blk_crypto_profile * profile,const struct blk_crypto_key * key,struct blk_crypto_keyslot ** slot_ptr)248 blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,
249 				    const struct blk_crypto_key *key,
250 				    struct blk_crypto_keyslot **slot_ptr)
251 {
252 	struct blk_crypto_keyslot *slot;
253 	int slot_idx;
254 	int err;
255 
256 	*slot_ptr = NULL;
257 
258 	/*
259 	 * If the device has no concept of "keyslots", then there is no need to
260 	 * get one.
261 	 */
262 	if (profile->num_slots == 0)
263 		return BLK_STS_OK;
264 
265 	down_read(&profile->lock);
266 	slot = blk_crypto_find_and_grab_keyslot(profile, key);
267 	up_read(&profile->lock);
268 	if (slot)
269 		goto success;
270 
271 	for (;;) {
272 		blk_crypto_hw_enter(profile);
273 		slot = blk_crypto_find_and_grab_keyslot(profile, key);
274 		if (slot) {
275 			blk_crypto_hw_exit(profile);
276 			goto success;
277 		}
278 
279 		/*
280 		 * If we're here, that means there wasn't a slot that was
281 		 * already programmed with the key. So try to program it.
282 		 */
283 		if (!list_empty(&profile->idle_slots))
284 			break;
285 
286 		blk_crypto_hw_exit(profile);
287 		wait_event(profile->idle_slots_wait_queue,
288 			   !list_empty(&profile->idle_slots));
289 	}
290 
291 	slot = list_first_entry(&profile->idle_slots, struct blk_crypto_keyslot,
292 				idle_slot_node);
293 	slot_idx = blk_crypto_keyslot_index(slot);
294 
295 	err = profile->ll_ops.keyslot_program(profile, key, slot_idx);
296 	if (err) {
297 		wake_up(&profile->idle_slots_wait_queue);
298 		blk_crypto_hw_exit(profile);
299 		return errno_to_blk_status(err);
300 	}
301 
302 	/* Move this slot to the hash list for the new key. */
303 	if (slot->key)
304 		hlist_del(&slot->hash_node);
305 	slot->key = key;
306 	hlist_add_head(&slot->hash_node,
307 		       blk_crypto_hash_bucket_for_key(profile, key));
308 
309 	atomic_set(&slot->slot_refs, 1);
310 
311 	blk_crypto_remove_slot_from_lru_list(slot);
312 
313 	blk_crypto_hw_exit(profile);
314 success:
315 	*slot_ptr = slot;
316 	return BLK_STS_OK;
317 }
318 
319 /**
320  * blk_crypto_put_keyslot() - Release a reference to a keyslot
321  * @slot: The keyslot to release the reference of
322  *
323  * Context: Any context.
324  */
blk_crypto_put_keyslot(struct blk_crypto_keyslot * slot)325 void blk_crypto_put_keyslot(struct blk_crypto_keyslot *slot)
326 {
327 	struct blk_crypto_profile *profile = slot->profile;
328 	unsigned long flags;
329 
330 	if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
331 					&profile->idle_slots_lock, flags)) {
332 		list_add_tail(&slot->idle_slot_node, &profile->idle_slots);
333 		spin_unlock_irqrestore(&profile->idle_slots_lock, flags);
334 		wake_up(&profile->idle_slots_wait_queue);
335 	}
336 }
337 
338 /**
339  * __blk_crypto_cfg_supported() - Check whether the given crypto profile
340  *				  supports the given crypto configuration.
341  * @profile: the crypto profile to check
342  * @cfg: the crypto configuration to check for
343  *
344  * Return: %true if @profile supports the given @cfg.
345  */
__blk_crypto_cfg_supported(struct blk_crypto_profile * profile,const struct blk_crypto_config * cfg)346 bool __blk_crypto_cfg_supported(struct blk_crypto_profile *profile,
347 				const struct blk_crypto_config *cfg)
348 {
349 	if (!profile)
350 		return false;
351 	if (!(profile->modes_supported[cfg->crypto_mode] & cfg->data_unit_size))
352 		return false;
353 	if (profile->max_dun_bytes_supported < cfg->dun_bytes)
354 		return false;
355 	return true;
356 }
357 
358 /*
359  * This is an internal function that evicts a key from an inline encryption
360  * device that can be either a real device or the blk-crypto-fallback "device".
361  * It is used only by blk_crypto_evict_key(); see that function for details.
362  */
__blk_crypto_evict_key(struct blk_crypto_profile * profile,const struct blk_crypto_key * key)363 int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
364 			   const struct blk_crypto_key *key)
365 {
366 	struct blk_crypto_keyslot *slot;
367 	int err;
368 
369 	if (profile->num_slots == 0) {
370 		if (profile->ll_ops.keyslot_evict) {
371 			blk_crypto_hw_enter(profile);
372 			err = profile->ll_ops.keyslot_evict(profile, key, -1);
373 			blk_crypto_hw_exit(profile);
374 			return err;
375 		}
376 		return 0;
377 	}
378 
379 	blk_crypto_hw_enter(profile);
380 	slot = blk_crypto_find_keyslot(profile, key);
381 	if (!slot) {
382 		/*
383 		 * Not an error, since a key not in use by I/O is not guaranteed
384 		 * to be in a keyslot.  There can be more keys than keyslots.
385 		 */
386 		err = 0;
387 		goto out;
388 	}
389 
390 	if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
391 		/* BUG: key is still in use by I/O */
392 		err = -EBUSY;
393 		goto out_remove;
394 	}
395 	err = profile->ll_ops.keyslot_evict(profile, key,
396 					    blk_crypto_keyslot_index(slot));
397 out_remove:
398 	/*
399 	 * Callers free the key even on error, so unlink the key from the hash
400 	 * table and clear slot->key even on error.
401 	 */
402 	hlist_del(&slot->hash_node);
403 	slot->key = NULL;
404 out:
405 	blk_crypto_hw_exit(profile);
406 	return err;
407 }
408 
409 /**
410  * blk_crypto_reprogram_all_keys() - Re-program all keyslots.
411  * @profile: The crypto profile
412  *
413  * Re-program all keyslots that are supposed to have a key programmed.  This is
414  * intended only for use by drivers for hardware that loses its keys on reset.
415  *
416  * Context: Process context. Takes and releases profile->lock.
417  */
blk_crypto_reprogram_all_keys(struct blk_crypto_profile * profile)418 void blk_crypto_reprogram_all_keys(struct blk_crypto_profile *profile)
419 {
420 	unsigned int slot;
421 
422 	if (profile->num_slots == 0)
423 		return;
424 
425 	/* This is for device initialization, so don't resume the device */
426 	down_write(&profile->lock);
427 	for (slot = 0; slot < profile->num_slots; slot++) {
428 		const struct blk_crypto_key *key = profile->slots[slot].key;
429 		int err;
430 
431 		if (!key)
432 			continue;
433 
434 		err = profile->ll_ops.keyslot_program(profile, key, slot);
435 		WARN_ON(err);
436 	}
437 	up_write(&profile->lock);
438 }
439 EXPORT_SYMBOL_GPL(blk_crypto_reprogram_all_keys);
440 
blk_crypto_profile_destroy(struct blk_crypto_profile * profile)441 void blk_crypto_profile_destroy(struct blk_crypto_profile *profile)
442 {
443 	if (!profile)
444 		return;
445 	lockdep_unregister_key(&profile->lockdep_key);
446 	kvfree(profile->slot_hashtable);
447 	kvfree_sensitive(profile->slots,
448 			 sizeof(profile->slots[0]) * profile->num_slots);
449 	memzero_explicit(profile, sizeof(*profile));
450 }
451 EXPORT_SYMBOL_GPL(blk_crypto_profile_destroy);
452 
blk_crypto_register(struct blk_crypto_profile * profile,struct request_queue * q)453 bool blk_crypto_register(struct blk_crypto_profile *profile,
454 			 struct request_queue *q)
455 {
456 	if (blk_integrity_queue_supports_integrity(q)) {
457 		pr_warn("Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n");
458 		return false;
459 	}
460 	q->crypto_profile = profile;
461 	return true;
462 }
463 EXPORT_SYMBOL_GPL(blk_crypto_register);
464 
465 /**
466  * blk_crypto_intersect_capabilities() - restrict supported crypto capabilities
467  *					 by child device
468  * @parent: the crypto profile for the parent device
469  * @child: the crypto profile for the child device, or NULL
470  *
471  * This clears all crypto capabilities in @parent that aren't set in @child.  If
472  * @child is NULL, then this clears all parent capabilities.
473  *
474  * Only use this when setting up the crypto profile for a layered device, before
475  * it's been exposed yet.
476  */
blk_crypto_intersect_capabilities(struct blk_crypto_profile * parent,const struct blk_crypto_profile * child)477 void blk_crypto_intersect_capabilities(struct blk_crypto_profile *parent,
478 				       const struct blk_crypto_profile *child)
479 {
480 	if (child) {
481 		unsigned int i;
482 
483 		parent->max_dun_bytes_supported =
484 			min(parent->max_dun_bytes_supported,
485 			    child->max_dun_bytes_supported);
486 		for (i = 0; i < ARRAY_SIZE(child->modes_supported); i++)
487 			parent->modes_supported[i] &= child->modes_supported[i];
488 	} else {
489 		parent->max_dun_bytes_supported = 0;
490 		memset(parent->modes_supported, 0,
491 		       sizeof(parent->modes_supported));
492 	}
493 }
494 EXPORT_SYMBOL_GPL(blk_crypto_intersect_capabilities);
495 
496 /**
497  * blk_crypto_has_capabilities() - Check whether @target supports at least all
498  *				   the crypto capabilities that @reference does.
499  * @target: the target profile
500  * @reference: the reference profile
501  *
502  * Return: %true if @target supports all the crypto capabilities of @reference.
503  */
blk_crypto_has_capabilities(const struct blk_crypto_profile * target,const struct blk_crypto_profile * reference)504 bool blk_crypto_has_capabilities(const struct blk_crypto_profile *target,
505 				 const struct blk_crypto_profile *reference)
506 {
507 	int i;
508 
509 	if (!reference)
510 		return true;
511 
512 	if (!target)
513 		return false;
514 
515 	for (i = 0; i < ARRAY_SIZE(target->modes_supported); i++) {
516 		if (reference->modes_supported[i] & ~target->modes_supported[i])
517 			return false;
518 	}
519 
520 	if (reference->max_dun_bytes_supported >
521 	    target->max_dun_bytes_supported)
522 		return false;
523 
524 	return true;
525 }
526 EXPORT_SYMBOL_GPL(blk_crypto_has_capabilities);
527 
528 /**
529  * blk_crypto_update_capabilities() - Update the capabilities of a crypto
530  *				      profile to match those of another crypto
531  *				      profile.
532  * @dst: The crypto profile whose capabilities to update.
533  * @src: The crypto profile whose capabilities this function will update @dst's
534  *	 capabilities to.
535  *
536  * Blk-crypto requires that crypto capabilities that were
537  * advertised when a bio was created continue to be supported by the
538  * device until that bio is ended. This is turn means that a device cannot
539  * shrink its advertised crypto capabilities without any explicit
540  * synchronization with upper layers. So if there's no such explicit
541  * synchronization, @src must support all the crypto capabilities that
542  * @dst does (i.e. we need blk_crypto_has_capabilities(@src, @dst)).
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  */
blk_crypto_update_capabilities(struct blk_crypto_profile * dst,const struct blk_crypto_profile * src)551 void blk_crypto_update_capabilities(struct blk_crypto_profile *dst,
552 				    const struct blk_crypto_profile *src)
553 {
554 	memcpy(dst->modes_supported, src->modes_supported,
555 	       sizeof(dst->modes_supported));
556 
557 	dst->max_dun_bytes_supported = src->max_dun_bytes_supported;
558 }
559 EXPORT_SYMBOL_GPL(blk_crypto_update_capabilities);
560