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/atomic.h>
  33 #include <linux/mutex.h>
  34 #include <linux/pm_runtime.h>
  35 #include <linux/wait.h>
  36 #include <linux/blkdev.h>
  37
  38 struct blk_ksm_keyslot {
  39         atomic_t slot_refs;
  40         struct list_head idle_slot_node;
  41         struct hlist_node hash_node;
  42         const struct blk_crypto_key *key;
  43         struct blk_keyslot_manager *ksm;
  44 };
  45
  46 static inline void blk_ksm_hw_enter(struct blk_keyslot_manager *ksm)
  47 {
  48         /*
  49          * Calling into the driver requires ksm->lock held and the device
  50          * resumed.  But we must resume the device first, since that can acquire
  51          * and release ksm->lock via blk_ksm_reprogram_all_keys().
  52          */
  53         if (ksm->dev)
  54                 pm_runtime_get_sync(ksm->dev);
  55         down_write(&ksm->lock);
  56 }
  57
  58 static inline void blk_ksm_hw_exit(struct blk_keyslot_manager *ksm)
  59 {
  60         up_write(&ksm->lock);
  61         if (ksm->dev)
  62                 pm_runtime_put_sync(ksm->dev);
  63 }
  64
  65 /**
  66  * blk_ksm_init() - Initialize a keyslot manager
  67  * @ksm: The keyslot_manager to initialize.
  68  * @num_slots: The number of key slots to manage.
  69  *
  70  * Allocate memory for keyslots and initialize a keyslot manager. Called by
  71  * e.g. storage drivers to set up a keyslot manager in their request_queue.
  72  *
  73  * Return: 0 on success, or else a negative error code.
  74  */
  75 int blk_ksm_init(struct blk_keyslot_manager *ksm, unsigned int num_slots)
  76 {
  77         unsigned int slot;
  78         unsigned int i;
  79         unsigned int slot_hashtable_size;
  80
  81         memset(ksm, 0, sizeof(*ksm));
  82
  83         if (num_slots == 0)
  84                 return -EINVAL;
  85
  86         ksm->slots = kvcalloc(num_slots, sizeof(ksm->slots[0]), GFP_KERNEL);
  87         if (!ksm->slots)
  88                 return -ENOMEM;
  89
  90         ksm->num_slots = num_slots;
  91
  92         init_rwsem(&ksm->lock);
  93
  94         init_waitqueue_head(&ksm->idle_slots_wait_queue);
  95         INIT_LIST_HEAD(&ksm->idle_slots);
  96
  97         for (slot = 0; slot < num_slots; slot++) {
  98                 ksm->slots[slot].ksm = ksm;
  99                 list_add_tail(&ksm->slots[slot].idle_slot_node,
 100                               &ksm->idle_slots);
 101         }
 102
 103         spin_lock_init(&ksm->idle_slots_lock);
 104
 105         slot_hashtable_size = roundup_pow_of_two(num_slots);
 106         /*
 107          * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
 108          * buckets.  This only makes a difference when there is only 1 keyslot.
 109          */
 110         if (slot_hashtable_size < 2)
 111                 slot_hashtable_size = 2;
 112
 113         ksm->log_slot_ht_size = ilog2(slot_hashtable_size);
 114         ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size,
 115                                              sizeof(ksm->slot_hashtable[0]),
 116                                              GFP_KERNEL);
 117         if (!ksm->slot_hashtable)
 118                 goto err_destroy_ksm;
 119         for (i = 0; i < slot_hashtable_size; i++)
 120                 INIT_HLIST_HEAD(&ksm->slot_hashtable[i]);
 121
 122         return 0;
 123
 124 err_destroy_ksm:
 125         blk_ksm_destroy(ksm);
 126         return -ENOMEM;
 127 }
 128 EXPORT_SYMBOL_GPL(blk_ksm_init);
 129
 130 static inline struct hlist_head *
 131 blk_ksm_hash_bucket_for_key(struct blk_keyslot_manager *ksm,
 132                             const struct blk_crypto_key *key)
 133 {
 134         return &ksm->slot_hashtable[hash_ptr(key, ksm->log_slot_ht_size)];
 135 }
 136
 137 static void blk_ksm_remove_slot_from_lru_list(struct blk_ksm_keyslot *slot)
 138 {
 139         struct blk_keyslot_manager *ksm = slot->ksm;
 140         unsigned long flags;
 141
 142         spin_lock_irqsave(&ksm->idle_slots_lock, flags);
 143         list_del(&slot->idle_slot_node);
 144         spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
 145 }
 146
 147 static struct blk_ksm_keyslot *blk_ksm_find_keyslot(
 148                                         struct blk_keyslot_manager *ksm,
 149                                         const struct blk_crypto_key *key)
 150 {
 151         const struct hlist_head *head = blk_ksm_hash_bucket_for_key(ksm, key);
 152         struct blk_ksm_keyslot *slotp;
 153
 154         hlist_for_each_entry(slotp, head, hash_node) {
 155                 if (slotp->key == key)
 156                         return slotp;
 157         }
 158         return NULL;
 159 }
 160
 161 static struct blk_ksm_keyslot *blk_ksm_find_and_grab_keyslot(
 162                                         struct blk_keyslot_manager *ksm,
 163                                         const struct blk_crypto_key *key)
 164 {
 165         struct blk_ksm_keyslot *slot;
 166
 167         slot = blk_ksm_find_keyslot(ksm, key);
 168         if (!slot)
 169                 return NULL;
 170         if (atomic_inc_return(&slot->slot_refs) == 1) {
 171                 /* Took first reference to this slot; remove it from LRU list */
 172                 blk_ksm_remove_slot_from_lru_list(slot);
 173         }
 174         return slot;
 175 }
 176
 177 unsigned int blk_ksm_get_slot_idx(struct blk_ksm_keyslot *slot)
 178 {
 179         return slot - slot->ksm->slots;
 180 }
 181 EXPORT_SYMBOL_GPL(blk_ksm_get_slot_idx);
 182
 183 /**
 184  * blk_ksm_get_slot_for_key() - Program a key into a keyslot.
 185  * @ksm: The keyslot manager to program the key into.
 186  * @key: Pointer to the key object to program, including the raw key, crypto
 187  *       mode, and data unit size.
 188  * @slot_ptr: A pointer to return the pointer of the allocated keyslot.
 189  *
 190  * Get a keyslot that's been programmed with the specified key.  If one already
 191  * exists, return it with incremented refcount.  Otherwise, wait for a keyslot
 192  * to become idle and program it.
 193  *
 194  * Context: Process context. Takes and releases ksm->lock.
 195  * Return: BLK_STS_OK on success (and keyslot is set to the pointer of the
 196  *         allocated keyslot), or some other blk_status_t otherwise (and
 197  *         keyslot is set to NULL).
 198  */
 199 blk_status_t blk_ksm_get_slot_for_key(struct blk_keyslot_manager *ksm,
 200                                       const struct blk_crypto_key *key,
 201                                       struct blk_ksm_keyslot **slot_ptr)
 202 {
 203         struct blk_ksm_keyslot *slot;
 204         int slot_idx;
 205         int err;
 206
 207         *slot_ptr = NULL;
 208         down_read(&ksm->lock);
 209         slot = blk_ksm_find_and_grab_keyslot(ksm, key);
 210         up_read(&ksm->lock);
 211         if (slot)
 212                 goto success;
 213
 214         for (;;) {
 215                 blk_ksm_hw_enter(ksm);
 216                 slot = blk_ksm_find_and_grab_keyslot(ksm, key);
 217                 if (slot) {
 218                         blk_ksm_hw_exit(ksm);
 219                         goto success;
 220                 }
 221
 222                 /*
 223                  * If we're here, that means there wasn't a slot that was
 224                  * already programmed with the key. So try to program it.
 225                  */
 226                 if (!list_empty(&ksm->idle_slots))
 227                         break;
 228
 229                 blk_ksm_hw_exit(ksm);
 230                 wait_event(ksm->idle_slots_wait_queue,
 231                            !list_empty(&ksm->idle_slots));
 232         }
 233
 234         slot = list_first_entry(&ksm->idle_slots, struct blk_ksm_keyslot,
 235                                 idle_slot_node);
 236         slot_idx = blk_ksm_get_slot_idx(slot);
 237
 238         err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot_idx);
 239         if (err) {
 240                 wake_up(&ksm->idle_slots_wait_queue);
 241                 blk_ksm_hw_exit(ksm);
 242                 return errno_to_blk_status(err);
 243         }
 244
 245         /* Move this slot to the hash list for the new key. */
 246         if (slot->key)
 247                 hlist_del(&slot->hash_node);
 248         slot->key = key;
 249         hlist_add_head(&slot->hash_node, blk_ksm_hash_bucket_for_key(ksm, key));
 250
 251         atomic_set(&slot->slot_refs, 1);
 252
 253         blk_ksm_remove_slot_from_lru_list(slot);
 254
 255         blk_ksm_hw_exit(ksm);
 256 success:
 257         *slot_ptr = slot;
 258         return BLK_STS_OK;
 259 }
 260
 261 /**
 262  * blk_ksm_put_slot() - Release a reference to a slot
 263  * @slot: The keyslot to release the reference of.
 264  *
 265  * Context: Any context.
 266  */
 267 void blk_ksm_put_slot(struct blk_ksm_keyslot *slot)
 268 {
 269         struct blk_keyslot_manager *ksm;
 270         unsigned long flags;
 271
 272         if (!slot)
 273                 return;
 274
 275         ksm = slot->ksm;
 276
 277         if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
 278                                         &ksm->idle_slots_lock, flags)) {
 279                 list_add_tail(&slot->idle_slot_node, &ksm->idle_slots);
 280                 spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
 281                 wake_up(&ksm->idle_slots_wait_queue);
 282         }
 283 }
 284
 285 /**
 286  * blk_ksm_crypto_cfg_supported() - Find out if a crypto configuration is
 287  *                                  supported by a ksm.
 288  * @ksm: The keyslot manager to check
 289  * @cfg: The crypto configuration to check for.
 290  *
 291  * Checks for crypto_mode/data unit size/dun bytes support.
 292  *
 293  * Return: Whether or not this ksm supports the specified crypto config.
 294  */
 295 bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
 296                                   const struct blk_crypto_config *cfg)
 297 {
 298         if (!ksm)
 299                 return false;
 300         if (!(ksm->crypto_modes_supported[cfg->crypto_mode] &
 301               cfg->data_unit_size))
 302                 return false;
 303         if (ksm->max_dun_bytes_supported < cfg->dun_bytes)
 304                 return false;
 305         return true;
 306 }
 307
 308 /**
 309  * blk_ksm_evict_key() - Evict a key from the lower layer device.
 310  * @ksm: The keyslot manager to evict from
 311  * @key: The key to evict
 312  *
 313  * Find the keyslot that the specified key was programmed into, and evict that
 314  * slot from the lower layer device. The slot must not be in use by any
 315  * in-flight IO when this function is called.
 316  *
 317  * Context: Process context. Takes and releases ksm->lock.
 318  * Return: 0 on success or if there's no keyslot with the specified key, -EBUSY
 319  *         if the keyslot is still in use, or another -errno value on other
 320  *         error.
 321  */
 322 int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
 323                       const struct blk_crypto_key *key)
 324 {
 325         struct blk_ksm_keyslot *slot;
 326         int err = 0;
 327
 328         blk_ksm_hw_enter(ksm);
 329         slot = blk_ksm_find_keyslot(ksm, key);
 330         if (!slot)
 331                 goto out_unlock;
 332
 333         if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
 334                 err = -EBUSY;
 335                 goto out_unlock;
 336         }
 337         err = ksm->ksm_ll_ops.keyslot_evict(ksm, key,
 338                                             blk_ksm_get_slot_idx(slot));
 339         if (err)
 340                 goto out_unlock;
 341
 342         hlist_del(&slot->hash_node);
 343         slot->key = NULL;
 344         err = 0;
 345 out_unlock:
 346         blk_ksm_hw_exit(ksm);
 347         return err;
 348 }
 349
 350 /**
 351  * blk_ksm_reprogram_all_keys() - Re-program all keyslots.
 352  * @ksm: The keyslot manager
 353  *
 354  * Re-program all keyslots that are supposed to have a key programmed.  This is
 355  * intended only for use by drivers for hardware that loses its keys on reset.
 356  *
 357  * Context: Process context. Takes and releases ksm->lock.
 358  */
 359 void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm)
 360 {
 361         unsigned int slot;
 362
 363         /* This is for device initialization, so don't resume the device */
 364         down_write(&ksm->lock);
 365         for (slot = 0; slot < ksm->num_slots; slot++) {
 366                 const struct blk_crypto_key *key = ksm->slots[slot].key;
 367                 int err;
 368
 369                 if (!key)
 370                         continue;
 371
 372                 err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot);
 373                 WARN_ON(err);
 374         }
 375         up_write(&ksm->lock);
 376 }
 377 EXPORT_SYMBOL_GPL(blk_ksm_reprogram_all_keys);
 378
 379 void blk_ksm_destroy(struct blk_keyslot_manager *ksm)
 380 {
 381         if (!ksm)
 382                 return;
 383         kvfree(ksm->slot_hashtable);
 384         kvfree_sensitive(ksm->slots, sizeof(ksm->slots[0]) * ksm->num_slots);
 385         memzero_explicit(ksm, sizeof(*ksm));
 386 }
 387 EXPORT_SYMBOL_GPL(blk_ksm_destroy);
 388
 389 bool blk_ksm_register(struct blk_keyslot_manager *ksm, struct request_queue *q)
 390 {
 391         if (blk_integrity_queue_supports_integrity(q)) {
 392                 pr_warn("Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n");
 393                 return false;
 394         }
 395         q->ksm = ksm;
 396         return true;
 397 }
 398 EXPORT_SYMBOL_GPL(blk_ksm_register);
 399
 400 void blk_ksm_unregister(struct request_queue *q)
 401 {
 402         q->ksm = NULL;
 403 }