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- // SPDX-License-Identifier: GPL-2.0
- /*
- * Copyright 2019 Google LLC
- */
- /**
- * DOC: The Keyslot Manager
- *
- * Many devices with inline encryption support have a limited number of "slots"
- * into which encryption contexts may be programmed, and requests can be tagged
- * with a slot number to specify the key to use for en/decryption.
- *
- * As the number of slots is limited, and programming keys is expensive on
- * many inline encryption hardware, we don't want to program the same key into
- * multiple slots - if multiple requests are using the same key, we want to
- * program just one slot with that key and use that slot for all requests.
- *
- * The keyslot manager manages these keyslots appropriately, and also acts as
- * an abstraction between the inline encryption hardware and the upper layers.
- *
- * Lower layer devices will set up a keyslot manager in their request queue
- * and tell it how to perform device specific operations like programming/
- * evicting keys from keyslots.
- *
- * Upper layers will call blk_ksm_get_slot_for_key() to program a
- * key into some slot in the inline encryption hardware.
- */
- #define pr_fmt(fmt) "blk-crypto: " fmt
- #include <linux/keyslot-manager.h>
- #include <linux/device.h>
- #include <linux/atomic.h>
- #include <linux/mutex.h>
- #include <linux/pm_runtime.h>
- #include <linux/wait.h>
- #include <linux/blkdev.h>
- struct blk_ksm_keyslot {
- atomic_t slot_refs;
- struct list_head idle_slot_node;
- struct hlist_node hash_node;
- const struct blk_crypto_key *key;
- struct blk_keyslot_manager *ksm;
- };
- static inline void blk_ksm_hw_enter(struct blk_keyslot_manager *ksm)
- {
- /*
- * Calling into the driver requires ksm->lock held and the device
- * resumed. But we must resume the device first, since that can acquire
- * and release ksm->lock via blk_ksm_reprogram_all_keys().
- */
- if (ksm->dev)
- pm_runtime_get_sync(ksm->dev);
- down_write(&ksm->lock);
- }
- static inline void blk_ksm_hw_exit(struct blk_keyslot_manager *ksm)
- {
- up_write(&ksm->lock);
- if (ksm->dev)
- pm_runtime_put_sync(ksm->dev);
- }
- static inline bool blk_ksm_is_passthrough(struct blk_keyslot_manager *ksm)
- {
- return ksm->num_slots == 0;
- }
- /**
- * blk_ksm_init() - Initialize a keyslot manager
- * @ksm: The keyslot_manager to initialize.
- * @num_slots: The number of key slots to manage.
- *
- * Allocate memory for keyslots and initialize a keyslot manager. Called by
- * e.g. storage drivers to set up a keyslot manager in their request_queue.
- *
- * Return: 0 on success, or else a negative error code.
- */
- int blk_ksm_init(struct blk_keyslot_manager *ksm, unsigned int num_slots)
- {
- unsigned int slot;
- unsigned int i;
- unsigned int slot_hashtable_size;
- memset(ksm, 0, sizeof(*ksm));
- if (num_slots == 0)
- return -EINVAL;
- ksm->slots = kvcalloc(num_slots, sizeof(ksm->slots[0]), GFP_KERNEL);
- if (!ksm->slots)
- return -ENOMEM;
- ksm->num_slots = num_slots;
- init_rwsem(&ksm->lock);
- init_waitqueue_head(&ksm->idle_slots_wait_queue);
- INIT_LIST_HEAD(&ksm->idle_slots);
- for (slot = 0; slot < num_slots; slot++) {
- ksm->slots[slot].ksm = ksm;
- list_add_tail(&ksm->slots[slot].idle_slot_node,
- &ksm->idle_slots);
- }
- spin_lock_init(&ksm->idle_slots_lock);
- slot_hashtable_size = roundup_pow_of_two(num_slots);
- /*
- * hash_ptr() assumes bits != 0, so ensure the hash table has at least 2
- * buckets. This only makes a difference when there is only 1 keyslot.
- */
- if (slot_hashtable_size < 2)
- slot_hashtable_size = 2;
- ksm->log_slot_ht_size = ilog2(slot_hashtable_size);
- ksm->slot_hashtable = kvmalloc_array(slot_hashtable_size,
- sizeof(ksm->slot_hashtable[0]),
- GFP_KERNEL);
- if (!ksm->slot_hashtable)
- goto err_destroy_ksm;
- for (i = 0; i < slot_hashtable_size; i++)
- INIT_HLIST_HEAD(&ksm->slot_hashtable[i]);
- return 0;
- err_destroy_ksm:
- blk_ksm_destroy(ksm);
- return -ENOMEM;
- }
- EXPORT_SYMBOL_GPL(blk_ksm_init);
- static void blk_ksm_destroy_callback(void *ksm)
- {
- blk_ksm_destroy(ksm);
- }
- /**
- * devm_blk_ksm_init() - Resource-managed blk_ksm_init()
- * @dev: The device which owns the blk_keyslot_manager.
- * @ksm: The blk_keyslot_manager to initialize.
- * @num_slots: The number of key slots to manage.
- *
- * Like blk_ksm_init(), but causes blk_ksm_destroy() to be called automatically
- * on driver detach.
- *
- * Return: 0 on success, or else a negative error code.
- */
- int devm_blk_ksm_init(struct device *dev, struct blk_keyslot_manager *ksm,
- unsigned int num_slots)
- {
- int err = blk_ksm_init(ksm, num_slots);
- if (err)
- return err;
- return devm_add_action_or_reset(dev, blk_ksm_destroy_callback, ksm);
- }
- EXPORT_SYMBOL_GPL(devm_blk_ksm_init);
- static inline struct hlist_head *
- blk_ksm_hash_bucket_for_key(struct blk_keyslot_manager *ksm,
- const struct blk_crypto_key *key)
- {
- return &ksm->slot_hashtable[hash_ptr(key, ksm->log_slot_ht_size)];
- }
- static void blk_ksm_remove_slot_from_lru_list(struct blk_ksm_keyslot *slot)
- {
- struct blk_keyslot_manager *ksm = slot->ksm;
- unsigned long flags;
- spin_lock_irqsave(&ksm->idle_slots_lock, flags);
- list_del(&slot->idle_slot_node);
- spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
- }
- static struct blk_ksm_keyslot *blk_ksm_find_keyslot(
- struct blk_keyslot_manager *ksm,
- const struct blk_crypto_key *key)
- {
- const struct hlist_head *head = blk_ksm_hash_bucket_for_key(ksm, key);
- struct blk_ksm_keyslot *slotp;
- hlist_for_each_entry(slotp, head, hash_node) {
- if (slotp->key == key)
- return slotp;
- }
- return NULL;
- }
- static struct blk_ksm_keyslot *blk_ksm_find_and_grab_keyslot(
- struct blk_keyslot_manager *ksm,
- const struct blk_crypto_key *key)
- {
- struct blk_ksm_keyslot *slot;
- slot = blk_ksm_find_keyslot(ksm, key);
- if (!slot)
- return NULL;
- if (atomic_inc_return(&slot->slot_refs) == 1) {
- /* Took first reference to this slot; remove it from LRU list */
- blk_ksm_remove_slot_from_lru_list(slot);
- }
- return slot;
- }
- unsigned int blk_ksm_get_slot_idx(struct blk_ksm_keyslot *slot)
- {
- return slot - slot->ksm->slots;
- }
- EXPORT_SYMBOL_GPL(blk_ksm_get_slot_idx);
- /**
- * blk_ksm_get_slot_for_key() - Program a key into a keyslot.
- * @ksm: The keyslot manager to program the key into.
- * @key: Pointer to the key object to program, including the raw key, crypto
- * mode, and data unit size.
- * @slot_ptr: A pointer to return the pointer of the allocated keyslot.
- *
- * Get a keyslot that's been programmed with the specified key. If one already
- * exists, return it with incremented refcount. Otherwise, wait for a keyslot
- * to become idle and program it.
- *
- * Context: Process context. Takes and releases ksm->lock.
- * Return: BLK_STS_OK on success (and keyslot is set to the pointer of the
- * allocated keyslot), or some other blk_status_t otherwise (and
- * keyslot is set to NULL).
- */
- blk_status_t blk_ksm_get_slot_for_key(struct blk_keyslot_manager *ksm,
- const struct blk_crypto_key *key,
- struct blk_ksm_keyslot **slot_ptr)
- {
- struct blk_ksm_keyslot *slot;
- int slot_idx;
- int err;
- *slot_ptr = NULL;
- if (blk_ksm_is_passthrough(ksm))
- return BLK_STS_OK;
- down_read(&ksm->lock);
- slot = blk_ksm_find_and_grab_keyslot(ksm, key);
- up_read(&ksm->lock);
- if (slot)
- goto success;
- for (;;) {
- blk_ksm_hw_enter(ksm);
- slot = blk_ksm_find_and_grab_keyslot(ksm, key);
- if (slot) {
- blk_ksm_hw_exit(ksm);
- goto success;
- }
- /*
- * If we're here, that means there wasn't a slot that was
- * already programmed with the key. So try to program it.
- */
- if (!list_empty(&ksm->idle_slots))
- break;
- blk_ksm_hw_exit(ksm);
- wait_event(ksm->idle_slots_wait_queue,
- !list_empty(&ksm->idle_slots));
- }
- slot = list_first_entry(&ksm->idle_slots, struct blk_ksm_keyslot,
- idle_slot_node);
- slot_idx = blk_ksm_get_slot_idx(slot);
- err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot_idx);
- if (err) {
- wake_up(&ksm->idle_slots_wait_queue);
- blk_ksm_hw_exit(ksm);
- return errno_to_blk_status(err);
- }
- /* Move this slot to the hash list for the new key. */
- if (slot->key)
- hlist_del(&slot->hash_node);
- slot->key = key;
- hlist_add_head(&slot->hash_node, blk_ksm_hash_bucket_for_key(ksm, key));
- atomic_set(&slot->slot_refs, 1);
- blk_ksm_remove_slot_from_lru_list(slot);
- blk_ksm_hw_exit(ksm);
- success:
- *slot_ptr = slot;
- return BLK_STS_OK;
- }
- /**
- * blk_ksm_put_slot() - Release a reference to a slot
- * @slot: The keyslot to release the reference of.
- *
- * Context: Any context.
- */
- void blk_ksm_put_slot(struct blk_ksm_keyslot *slot)
- {
- struct blk_keyslot_manager *ksm;
- unsigned long flags;
- if (!slot)
- return;
- ksm = slot->ksm;
- if (atomic_dec_and_lock_irqsave(&slot->slot_refs,
- &ksm->idle_slots_lock, flags)) {
- list_add_tail(&slot->idle_slot_node, &ksm->idle_slots);
- spin_unlock_irqrestore(&ksm->idle_slots_lock, flags);
- wake_up(&ksm->idle_slots_wait_queue);
- }
- }
- /**
- * blk_ksm_crypto_cfg_supported() - Find out if a crypto configuration is
- * supported by a ksm.
- * @ksm: The keyslot manager to check
- * @cfg: The crypto configuration to check for.
- *
- * Checks for crypto_mode/data unit size/dun bytes support.
- *
- * Return: Whether or not this ksm supports the specified crypto config.
- */
- bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
- const struct blk_crypto_config *cfg)
- {
- if (!ksm)
- return false;
- if (!(ksm->crypto_modes_supported[cfg->crypto_mode] &
- cfg->data_unit_size))
- return false;
- if (ksm->max_dun_bytes_supported < cfg->dun_bytes)
- return false;
- if (cfg->is_hw_wrapped) {
- if (!(ksm->features & BLK_CRYPTO_FEATURE_WRAPPED_KEYS))
- return false;
- } else {
- if (!(ksm->features & BLK_CRYPTO_FEATURE_STANDARD_KEYS))
- return false;
- }
- return true;
- }
- /**
- * blk_ksm_evict_key() - Evict a key from the lower layer device.
- * @ksm: The keyslot manager to evict from
- * @key: The key to evict
- *
- * Find the keyslot that the specified key was programmed into, and evict that
- * slot from the lower layer device. The slot must not be in use by any
- * in-flight IO when this function is called.
- *
- * Context: Process context. Takes and releases ksm->lock.
- * Return: 0 on success or if there's no keyslot with the specified key, -EBUSY
- * if the keyslot is still in use, or another -errno value on other
- * error.
- */
- int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
- const struct blk_crypto_key *key)
- {
- struct blk_ksm_keyslot *slot;
- int err = 0;
- if (blk_ksm_is_passthrough(ksm)) {
- if (ksm->ksm_ll_ops.keyslot_evict) {
- blk_ksm_hw_enter(ksm);
- err = ksm->ksm_ll_ops.keyslot_evict(ksm, key, -1);
- blk_ksm_hw_exit(ksm);
- return err;
- }
- return 0;
- }
- blk_ksm_hw_enter(ksm);
- slot = blk_ksm_find_keyslot(ksm, key);
- if (!slot)
- goto out_unlock;
- if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
- err = -EBUSY;
- goto out_unlock;
- }
- err = ksm->ksm_ll_ops.keyslot_evict(ksm, key,
- blk_ksm_get_slot_idx(slot));
- if (err)
- goto out_unlock;
- hlist_del(&slot->hash_node);
- slot->key = NULL;
- err = 0;
- out_unlock:
- blk_ksm_hw_exit(ksm);
- return err;
- }
- /**
- * blk_ksm_reprogram_all_keys() - Re-program all keyslots.
- * @ksm: The keyslot manager
- *
- * Re-program all keyslots that are supposed to have a key programmed. This is
- * intended only for use by drivers for hardware that loses its keys on reset.
- *
- * Context: Process context. Takes and releases ksm->lock.
- */
- void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm)
- {
- unsigned int slot;
- if (blk_ksm_is_passthrough(ksm))
- return;
- /* This is for device initialization, so don't resume the device */
- down_write(&ksm->lock);
- for (slot = 0; slot < ksm->num_slots; slot++) {
- const struct blk_crypto_key *key = ksm->slots[slot].key;
- int err;
- if (!key)
- continue;
- err = ksm->ksm_ll_ops.keyslot_program(ksm, key, slot);
- WARN_ON(err);
- }
- up_write(&ksm->lock);
- }
- EXPORT_SYMBOL_GPL(blk_ksm_reprogram_all_keys);
- void blk_ksm_destroy(struct blk_keyslot_manager *ksm)
- {
- if (!ksm)
- return;
- kvfree(ksm->slot_hashtable);
- kvfree_sensitive(ksm->slots, sizeof(ksm->slots[0]) * ksm->num_slots);
- memzero_explicit(ksm, sizeof(*ksm));
- }
- EXPORT_SYMBOL_GPL(blk_ksm_destroy);
- bool blk_ksm_register(struct blk_keyslot_manager *ksm, struct request_queue *q)
- {
- if (blk_integrity_queue_supports_integrity(q)) {
- pr_warn("Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n");
- return false;
- }
- q->ksm = ksm;
- return true;
- }
- EXPORT_SYMBOL_GPL(blk_ksm_register);
- void blk_ksm_unregister(struct request_queue *q)
- {
- q->ksm = NULL;
- }
- /**
- * blk_ksm_derive_raw_secret() - Derive software secret from wrapped key
- * @ksm: The keyslot manager
- * @wrapped_key: The wrapped key
- * @wrapped_key_size: Size of the wrapped key in bytes
- * @secret: (output) the software secret
- * @secret_size: (output) the number of secret bytes to derive
- *
- * Given a hardware-wrapped key, ask the hardware to derive a secret which
- * software can use for cryptographic tasks other than inline encryption. The
- * derived secret is guaranteed to be cryptographically isolated from the key
- * with which any inline encryption with this wrapped key would actually be
- * done. I.e., both will be derived from the unwrapped key.
- *
- * Return: 0 on success, -EOPNOTSUPP if hardware-wrapped keys are unsupported,
- * or another -errno code.
- */
- int blk_ksm_derive_raw_secret(struct blk_keyslot_manager *ksm,
- const u8 *wrapped_key,
- unsigned int wrapped_key_size,
- u8 *secret, unsigned int secret_size)
- {
- int err;
- if (ksm->ksm_ll_ops.derive_raw_secret) {
- blk_ksm_hw_enter(ksm);
- err = ksm->ksm_ll_ops.derive_raw_secret(ksm, wrapped_key,
- wrapped_key_size,
- secret, secret_size);
- blk_ksm_hw_exit(ksm);
- } else {
- err = -EOPNOTSUPP;
- }
- return err;
- }
- EXPORT_SYMBOL_GPL(blk_ksm_derive_raw_secret);
- /**
- * blk_ksm_intersect_modes() - restrict supported modes by child device
- * @parent: The keyslot manager for parent device
- * @child: The keyslot manager for child device, or NULL
- *
- * Clear any crypto mode support bits in @parent that aren't set in @child.
- * If @child is NULL, then all parent bits are cleared.
- *
- * Only use this when setting up the keyslot manager for a layered device,
- * before it's been exposed yet.
- */
- void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
- const struct blk_keyslot_manager *child)
- {
- if (child) {
- unsigned int i;
- parent->max_dun_bytes_supported =
- min(parent->max_dun_bytes_supported,
- child->max_dun_bytes_supported);
- for (i = 0; i < ARRAY_SIZE(child->crypto_modes_supported);
- i++) {
- parent->crypto_modes_supported[i] &=
- child->crypto_modes_supported[i];
- }
- parent->features &= child->features;
- } else {
- parent->max_dun_bytes_supported = 0;
- memset(parent->crypto_modes_supported, 0,
- sizeof(parent->crypto_modes_supported));
- parent->features = 0;
- }
- }
- EXPORT_SYMBOL_GPL(blk_ksm_intersect_modes);
- /**
- * blk_ksm_is_superset() - Check if a KSM supports a superset of crypto modes
- * and DUN bytes that another KSM supports. Here,
- * "superset" refers to the mathematical meaning of the
- * word - i.e. if two KSMs have the *same* capabilities,
- * they *are* considered supersets of each other.
- * @ksm_superset: The KSM that we want to verify is a superset
- * @ksm_subset: The KSM that we want to verify is a subset
- *
- * Return: True if @ksm_superset supports a superset of the crypto modes and DUN
- * bytes that @ksm_subset supports.
- */
- bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
- struct blk_keyslot_manager *ksm_subset)
- {
- int i;
- if (!ksm_subset)
- return true;
- if (!ksm_superset)
- return false;
- for (i = 0; i < ARRAY_SIZE(ksm_superset->crypto_modes_supported); i++) {
- if (ksm_subset->crypto_modes_supported[i] &
- (~ksm_superset->crypto_modes_supported[i])) {
- return false;
- }
- }
- if (ksm_subset->max_dun_bytes_supported >
- ksm_superset->max_dun_bytes_supported) {
- return false;
- }
- if (ksm_subset->features & ~ksm_superset->features)
- return false;
- return true;
- }
- EXPORT_SYMBOL_GPL(blk_ksm_is_superset);
- /**
- * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
- * another KSM
- * @target_ksm: The KSM whose restrictions to update.
- * @reference_ksm: The KSM to whose restrictions this function will update
- * @target_ksm's restrictions to.
- *
- * Blk-crypto requires that crypto capabilities that were
- * advertised when a bio was created continue to be supported by the
- * device until that bio is ended. This is turn means that a device cannot
- * shrink its advertised crypto capabilities without any explicit
- * synchronization with upper layers. So if there's no such explicit
- * synchronization, @reference_ksm must support all the crypto capabilities that
- * @target_ksm does
- * (i.e. we need blk_ksm_is_superset(@reference_ksm, @target_ksm) == true).
- *
- * Note also that as long as the crypto capabilities are being expanded, the
- * order of updates becoming visible is not important because it's alright
- * for blk-crypto to see stale values - they only cause blk-crypto to
- * believe that a crypto capability isn't supported when it actually is (which
- * might result in blk-crypto-fallback being used if available, or the bio being
- * failed).
- */
- void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
- struct blk_keyslot_manager *reference_ksm)
- {
- memcpy(target_ksm->crypto_modes_supported,
- reference_ksm->crypto_modes_supported,
- sizeof(target_ksm->crypto_modes_supported));
- target_ksm->max_dun_bytes_supported =
- reference_ksm->max_dun_bytes_supported;
- target_ksm->features = reference_ksm->features;
- }
- EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
- /**
- * blk_ksm_init_passthrough() - Init a passthrough keyslot manager
- * @ksm: The keyslot manager to init
- *
- * Initialize a passthrough keyslot manager.
- * Called by e.g. storage drivers to set up a keyslot manager in their
- * request_queue, when the storage driver wants to manage its keys by itself.
- * This is useful for inline encryption hardware that doesn't have the concept
- * of keyslots, and for layered devices.
- */
- void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm)
- {
- memset(ksm, 0, sizeof(*ksm));
- init_rwsem(&ksm->lock);
- }
- EXPORT_SYMBOL_GPL(blk_ksm_init_passthrough);
|