block/keyslot-manager.c

   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
  39 struct 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
  47 static 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
  59 static 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
  66 static 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  */
  81 int 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
 130 err_destroy_ksm:
 131         blk_ksm_destroy(ksm);
 132         return -ENOMEM;
 133 }
 134 EXPORT_SYMBOL_GPL(blk_ksm_init);
 135
 136 static 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  */
 152 int 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 }
 162 EXPORT_SYMBOL_GPL(devm_blk_ksm_init);
 163
 164 static inline struct hlist_head *
 165 blk_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
 171 static 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
 181 static 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
 195 static 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
 211 unsigned int blk_ksm_get_slot_idx(struct blk_ksm_keyslot *slot)
 212 {
 213         return slot - slot->ksm->slots;
 214 }
 215 EXPORT_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  */
 233 blk_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);
 294 success:
 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  */
 305 void 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  */
 333 bool 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  */
 360 int 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;
 393 out_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  */
 407 void 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 }
 428 EXPORT_SYMBOL_GPL(blk_ksm_reprogram_all_keys);
 429
 430 void 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 }
 438 EXPORT_SYMBOL_GPL(blk_ksm_destroy);
 439
 440 bool 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 }
 449 EXPORT_SYMBOL_GPL(blk_ksm_register);
 450
 451 void 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  */
 467 void 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 }
 487 EXPORT_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  */
 501 bool 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 }
 526 EXPORT_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  */
 551 void 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 }
 561 EXPORT_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  */
 573 void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm)
 574 {
 575         memset(ksm, 0, sizeof(*ksm));
 576         init_rwsem(&ksm->lock);
 577 }
 578 EXPORT_SYMBOL_GPL(blk_ksm_init_passthrough);