keyring.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Filesystem-level keyring for fscrypt
   4 *
   5 * Copyright 2019 Google LLC
   6 */
   7
   8/*
   9 * This file implements management of fscrypt master keys in the
  10 * filesystem-level keyring, including the ioctls:
  11 *
  12 * - FS_IOC_ADD_ENCRYPTION_KEY
  13 * - FS_IOC_REMOVE_ENCRYPTION_KEY
  14 * - FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS
  15 * - FS_IOC_GET_ENCRYPTION_KEY_STATUS
  16 *
  17 * See the "User API" section of Documentation/filesystems/fscrypt.rst for more
  18 * information about these ioctls.
  19 */
  20
  21#include <crypto/skcipher.h>
  22#include <linux/export.h>
  23#include <linux/key-type.h>
  24#include <linux/once.h>
  25#include <linux/random.h>
  26#include <linux/seq_file.h>
  27#include <linux/unaligned.h>
  28
  29#include "fscrypt_private.h"
  30
  31/* The master encryption keys for a filesystem (->s_master_keys) */
  32struct fscrypt_keyring {
  33	/*
  34	 * Lock that protects ->key_hashtable.  It does *not* protect the
  35	 * fscrypt_master_key structs themselves.
  36	 */
  37	spinlock_t lock;
  38
  39	/* Hash table that maps fscrypt_key_specifier to fscrypt_master_key */
  40	struct hlist_head key_hashtable[128];
  41};
  42
  43static void wipe_master_key_secret(struct fscrypt_master_key_secret *secret)
  44{
  45	memzero_explicit(secret, sizeof(*secret));
  46}
  47
  48static void move_master_key_secret(struct fscrypt_master_key_secret *dst,
  49				   struct fscrypt_master_key_secret *src)
  50{
  51	memcpy(dst, src, sizeof(*dst));
  52	memzero_explicit(src, sizeof(*src));
  53}
  54
  55static void fscrypt_free_master_key(struct rcu_head *head)
  56{
  57	struct fscrypt_master_key *mk =
  58		container_of(head, struct fscrypt_master_key, mk_rcu_head);
  59	/*
  60	 * The master key secret and any embedded subkeys should have already
  61	 * been wiped when the last active reference to the fscrypt_master_key
  62	 * struct was dropped; doing it here would be unnecessarily late.
  63	 * Nevertheless, use kfree_sensitive() in case anything was missed.
  64	 */
  65	kfree_sensitive(mk);
  66}
  67
  68void fscrypt_put_master_key(struct fscrypt_master_key *mk)
  69{
  70	if (!refcount_dec_and_test(&mk->mk_struct_refs))
  71		return;
  72	/*
  73	 * No structural references left, so free ->mk_users, and also free the
  74	 * fscrypt_master_key struct itself after an RCU grace period ensures
  75	 * that concurrent keyring lookups can no longer find it.
  76	 */
  77	WARN_ON_ONCE(refcount_read(&mk->mk_active_refs) != 0);
  78	if (mk->mk_users) {
  79		/* Clear the keyring so the quota gets released right away. */
  80		keyring_clear(mk->mk_users);
  81		key_put(mk->mk_users);
  82		mk->mk_users = NULL;
  83	}
  84	call_rcu(&mk->mk_rcu_head, fscrypt_free_master_key);
  85}
  86
  87void fscrypt_put_master_key_activeref(struct super_block *sb,
  88				      struct fscrypt_master_key *mk)
  89{
  90	size_t i;
  91
  92	if (!refcount_dec_and_test(&mk->mk_active_refs))
  93		return;
  94	/*
  95	 * No active references left, so complete the full removal of this
  96	 * fscrypt_master_key struct by removing it from the keyring and
  97	 * destroying any subkeys embedded in it.
  98	 */
  99
 100	if (WARN_ON_ONCE(!sb->s_master_keys))
 101		return;
 102	spin_lock(&sb->s_master_keys->lock);
 103	hlist_del_rcu(&mk->mk_node);
 104	spin_unlock(&sb->s_master_keys->lock);
 105
 106	/*
 107	 * ->mk_active_refs == 0 implies that ->mk_present is false and
 108	 * ->mk_decrypted_inodes is empty.
 109	 */
 110	WARN_ON_ONCE(mk->mk_present);
 111	WARN_ON_ONCE(!list_empty(&mk->mk_decrypted_inodes));
 112
 113	for (i = 0; i <= FSCRYPT_MODE_MAX; i++) {
 114		fscrypt_destroy_prepared_key(
 115				sb, &mk->mk_direct_keys[i]);
 116		fscrypt_destroy_prepared_key(
 117				sb, &mk->mk_iv_ino_lblk_64_keys[i]);
 118		fscrypt_destroy_prepared_key(
 119				sb, &mk->mk_iv_ino_lblk_32_keys[i]);
 120	}
 121	memzero_explicit(&mk->mk_ino_hash_key,
 122			 sizeof(mk->mk_ino_hash_key));
 123	mk->mk_ino_hash_key_initialized = false;
 124
 125	/* Drop the structural ref associated with the active refs. */
 126	fscrypt_put_master_key(mk);
 127}
 128
 129/*
 130 * This transitions the key state from present to incompletely removed, and then
 131 * potentially to absent (depending on whether inodes remain).
 132 */
 133static void fscrypt_initiate_key_removal(struct super_block *sb,
 134					 struct fscrypt_master_key *mk)
 135{
 136	WRITE_ONCE(mk->mk_present, false);
 137	wipe_master_key_secret(&mk->mk_secret);
 138	fscrypt_put_master_key_activeref(sb, mk);
 139}
 140
 141static inline bool valid_key_spec(const struct fscrypt_key_specifier *spec)
 142{
 143	if (spec->__reserved)
 144		return false;
 145	return master_key_spec_len(spec) != 0;
 146}
 147
 148static int fscrypt_user_key_instantiate(struct key *key,
 149					struct key_preparsed_payload *prep)
 150{
 151	/*
 152	 * We just charge FSCRYPT_MAX_RAW_KEY_SIZE bytes to the user's key quota
 153	 * for each key, regardless of the exact key size.  The amount of memory
 154	 * actually used is greater than the size of the raw key anyway.
 155	 */
 156	return key_payload_reserve(key, FSCRYPT_MAX_RAW_KEY_SIZE);
 157}
 158
 159static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m)
 160{
 161	seq_puts(m, key->description);
 162}
 163
 164/*
 165 * Type of key in ->mk_users.  Each key of this type represents a particular
 166 * user who has added a particular master key.
 167 *
 168 * Note that the name of this key type really should be something like
 169 * ".fscrypt-user" instead of simply ".fscrypt".  But the shorter name is chosen
 170 * mainly for simplicity of presentation in /proc/keys when read by a non-root
 171 * user.  And it is expected to be rare that a key is actually added by multiple
 172 * users, since users should keep their encryption keys confidential.
 173 */
 174static struct key_type key_type_fscrypt_user = {
 175	.name			= ".fscrypt",
 176	.instantiate		= fscrypt_user_key_instantiate,
 177	.describe		= fscrypt_user_key_describe,
 178};
 179
 180#define FSCRYPT_MK_USERS_DESCRIPTION_SIZE	\
 181	(CONST_STRLEN("fscrypt-") + 2 * FSCRYPT_KEY_IDENTIFIER_SIZE + \
 182	 CONST_STRLEN("-users") + 1)
 183
 184#define FSCRYPT_MK_USER_DESCRIPTION_SIZE	\
 185	(2 * FSCRYPT_KEY_IDENTIFIER_SIZE + CONST_STRLEN(".uid.") + 10 + 1)
 186
 187static void format_mk_users_keyring_description(
 188			char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE],
 189			const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
 190{
 191	sprintf(description, "fscrypt-%*phN-users",
 192		FSCRYPT_KEY_IDENTIFIER_SIZE, mk_identifier);
 193}
 194
 195static void format_mk_user_description(
 196			char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE],
 197			const u8 mk_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
 198{
 199
 200	sprintf(description, "%*phN.uid.%u", FSCRYPT_KEY_IDENTIFIER_SIZE,
 201		mk_identifier, __kuid_val(current_fsuid()));
 202}
 203
 204/* Create ->s_master_keys if needed.  Synchronized by fscrypt_add_key_mutex. */
 205static int allocate_filesystem_keyring(struct super_block *sb)
 206{
 207	struct fscrypt_keyring *keyring;
 208
 209	if (sb->s_master_keys)
 210		return 0;
 211
 212	keyring = kzalloc(sizeof(*keyring), GFP_KERNEL);
 213	if (!keyring)
 214		return -ENOMEM;
 215	spin_lock_init(&keyring->lock);
 216	/*
 217	 * Pairs with the smp_load_acquire() in fscrypt_find_master_key().
 218	 * I.e., here we publish ->s_master_keys with a RELEASE barrier so that
 219	 * concurrent tasks can ACQUIRE it.
 220	 */
 221	smp_store_release(&sb->s_master_keys, keyring);
 222	return 0;
 223}
 224
 225/*
 226 * Release all encryption keys that have been added to the filesystem, along
 227 * with the keyring that contains them.
 228 *
 229 * This is called at unmount time, after all potentially-encrypted inodes have
 230 * been evicted.  The filesystem's underlying block device(s) are still
 231 * available at this time; this is important because after user file accesses
 232 * have been allowed, this function may need to evict keys from the keyslots of
 233 * an inline crypto engine, which requires the block device(s).
 234 */
 235void fscrypt_destroy_keyring(struct super_block *sb)
 236{
 237	struct fscrypt_keyring *keyring = sb->s_master_keys;
 238	size_t i;
 239
 240	if (!keyring)
 241		return;
 242
 243	for (i = 0; i < ARRAY_SIZE(keyring->key_hashtable); i++) {
 244		struct hlist_head *bucket = &keyring->key_hashtable[i];
 245		struct fscrypt_master_key *mk;
 246		struct hlist_node *tmp;
 247
 248		hlist_for_each_entry_safe(mk, tmp, bucket, mk_node) {
 249			/*
 250			 * Since all potentially-encrypted inodes were already
 251			 * evicted, every key remaining in the keyring should
 252			 * have an empty inode list, and should only still be in
 253			 * the keyring due to the single active ref associated
 254			 * with ->mk_present.  There should be no structural
 255			 * refs beyond the one associated with the active ref.
 256			 */
 257			WARN_ON_ONCE(refcount_read(&mk->mk_active_refs) != 1);
 258			WARN_ON_ONCE(refcount_read(&mk->mk_struct_refs) != 1);
 259			WARN_ON_ONCE(!mk->mk_present);
 260			fscrypt_initiate_key_removal(sb, mk);
 261		}
 262	}
 263	kfree_sensitive(keyring);
 264	sb->s_master_keys = NULL;
 265}
 266
 267static struct hlist_head *
 268fscrypt_mk_hash_bucket(struct fscrypt_keyring *keyring,
 269		       const struct fscrypt_key_specifier *mk_spec)
 270{
 271	/*
 272	 * Since key specifiers should be "random" values, it is sufficient to
 273	 * use a trivial hash function that just takes the first several bits of
 274	 * the key specifier.
 275	 */
 276	unsigned long i = get_unaligned((unsigned long *)&mk_spec->u);
 277
 278	return &keyring->key_hashtable[i % ARRAY_SIZE(keyring->key_hashtable)];
 279}
 280
 281/*
 282 * Find the specified master key struct in ->s_master_keys and take a structural
 283 * ref to it.  The structural ref guarantees that the key struct continues to
 284 * exist, but it does *not* guarantee that ->s_master_keys continues to contain
 285 * the key struct.  The structural ref needs to be dropped by
 286 * fscrypt_put_master_key().  Returns NULL if the key struct is not found.
 287 */
 288struct fscrypt_master_key *
 289fscrypt_find_master_key(struct super_block *sb,
 290			const struct fscrypt_key_specifier *mk_spec)
 291{
 292	struct fscrypt_keyring *keyring;
 293	struct hlist_head *bucket;
 294	struct fscrypt_master_key *mk;
 295
 296	/*
 297	 * Pairs with the smp_store_release() in allocate_filesystem_keyring().
 298	 * I.e., another task can publish ->s_master_keys concurrently,
 299	 * executing a RELEASE barrier.  We need to use smp_load_acquire() here
 300	 * to safely ACQUIRE the memory the other task published.
 301	 */
 302	keyring = smp_load_acquire(&sb->s_master_keys);
 303	if (keyring == NULL)
 304		return NULL; /* No keyring yet, so no keys yet. */
 305
 306	bucket = fscrypt_mk_hash_bucket(keyring, mk_spec);
 307	rcu_read_lock();
 308	switch (mk_spec->type) {
 309	case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
 310		hlist_for_each_entry_rcu(mk, bucket, mk_node) {
 311			if (mk->mk_spec.type ==
 312				FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
 313			    memcmp(mk->mk_spec.u.descriptor,
 314				   mk_spec->u.descriptor,
 315				   FSCRYPT_KEY_DESCRIPTOR_SIZE) == 0 &&
 316			    refcount_inc_not_zero(&mk->mk_struct_refs))
 317				goto out;
 318		}
 319		break;
 320	case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
 321		hlist_for_each_entry_rcu(mk, bucket, mk_node) {
 322			if (mk->mk_spec.type ==
 323				FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER &&
 324			    memcmp(mk->mk_spec.u.identifier,
 325				   mk_spec->u.identifier,
 326				   FSCRYPT_KEY_IDENTIFIER_SIZE) == 0 &&
 327			    refcount_inc_not_zero(&mk->mk_struct_refs))
 328				goto out;
 329		}
 330		break;
 331	}
 332	mk = NULL;
 333out:
 334	rcu_read_unlock();
 335	return mk;
 336}
 337
 338static int allocate_master_key_users_keyring(struct fscrypt_master_key *mk)
 339{
 340	char description[FSCRYPT_MK_USERS_DESCRIPTION_SIZE];
 341	struct key *keyring;
 342
 343	format_mk_users_keyring_description(description,
 344					    mk->mk_spec.u.identifier);
 345	keyring = keyring_alloc(description, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
 346				current_cred(), KEY_POS_SEARCH |
 347				  KEY_USR_SEARCH | KEY_USR_READ | KEY_USR_VIEW,
 348				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
 349	if (IS_ERR(keyring))
 350		return PTR_ERR(keyring);
 351
 352	mk->mk_users = keyring;
 353	return 0;
 354}
 355
 356/*
 357 * Find the current user's "key" in the master key's ->mk_users.
 358 * Returns ERR_PTR(-ENOKEY) if not found.
 359 */
 360static struct key *find_master_key_user(struct fscrypt_master_key *mk)
 361{
 362	char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
 363	key_ref_t keyref;
 364
 365	format_mk_user_description(description, mk->mk_spec.u.identifier);
 366
 367	/*
 368	 * We need to mark the keyring reference as "possessed" so that we
 369	 * acquire permission to search it, via the KEY_POS_SEARCH permission.
 370	 */
 371	keyref = keyring_search(make_key_ref(mk->mk_users, true /*possessed*/),
 372				&key_type_fscrypt_user, description, false);
 373	if (IS_ERR(keyref)) {
 374		if (PTR_ERR(keyref) == -EAGAIN || /* not found */
 375		    PTR_ERR(keyref) == -EKEYREVOKED) /* recently invalidated */
 376			keyref = ERR_PTR(-ENOKEY);
 377		return ERR_CAST(keyref);
 378	}
 379	return key_ref_to_ptr(keyref);
 380}
 381
 382/*
 383 * Give the current user a "key" in ->mk_users.  This charges the user's quota
 384 * and marks the master key as added by the current user, so that it cannot be
 385 * removed by another user with the key.  Either ->mk_sem must be held for
 386 * write, or the master key must be still undergoing initialization.
 387 */
 388static int add_master_key_user(struct fscrypt_master_key *mk)
 389{
 390	char description[FSCRYPT_MK_USER_DESCRIPTION_SIZE];
 391	struct key *mk_user;
 392	int err;
 393
 394	format_mk_user_description(description, mk->mk_spec.u.identifier);
 395	mk_user = key_alloc(&key_type_fscrypt_user, description,
 396			    current_fsuid(), current_gid(), current_cred(),
 397			    KEY_POS_SEARCH | KEY_USR_VIEW, 0, NULL);
 398	if (IS_ERR(mk_user))
 399		return PTR_ERR(mk_user);
 400
 401	err = key_instantiate_and_link(mk_user, NULL, 0, mk->mk_users, NULL);
 402	key_put(mk_user);
 403	return err;
 404}
 405
 406/*
 407 * Remove the current user's "key" from ->mk_users.
 408 * ->mk_sem must be held for write.
 409 *
 410 * Returns 0 if removed, -ENOKEY if not found, or another -errno code.
 411 */
 412static int remove_master_key_user(struct fscrypt_master_key *mk)
 413{
 414	struct key *mk_user;
 415	int err;
 416
 417	mk_user = find_master_key_user(mk);
 418	if (IS_ERR(mk_user))
 419		return PTR_ERR(mk_user);
 420	err = key_unlink(mk->mk_users, mk_user);
 421	key_put(mk_user);
 422	return err;
 423}
 424
 425/*
 426 * Allocate a new fscrypt_master_key, transfer the given secret over to it, and
 427 * insert it into sb->s_master_keys.
 428 */
 429static int add_new_master_key(struct super_block *sb,
 430			      struct fscrypt_master_key_secret *secret,
 431			      const struct fscrypt_key_specifier *mk_spec)
 432{
 433	struct fscrypt_keyring *keyring = sb->s_master_keys;
 434	struct fscrypt_master_key *mk;
 435	int err;
 436
 437	mk = kzalloc(sizeof(*mk), GFP_KERNEL);
 438	if (!mk)
 439		return -ENOMEM;
 440
 441	init_rwsem(&mk->mk_sem);
 442	refcount_set(&mk->mk_struct_refs, 1);
 443	mk->mk_spec = *mk_spec;
 444
 445	INIT_LIST_HEAD(&mk->mk_decrypted_inodes);
 446	spin_lock_init(&mk->mk_decrypted_inodes_lock);
 447
 448	if (mk_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
 449		err = allocate_master_key_users_keyring(mk);
 450		if (err)
 451			goto out_put;
 452		err = add_master_key_user(mk);
 453		if (err)
 454			goto out_put;
 455	}
 456
 457	move_master_key_secret(&mk->mk_secret, secret);
 458	mk->mk_present = true;
 459	refcount_set(&mk->mk_active_refs, 1); /* ->mk_present is true */
 460
 461	spin_lock(&keyring->lock);
 462	hlist_add_head_rcu(&mk->mk_node,
 463			   fscrypt_mk_hash_bucket(keyring, mk_spec));
 464	spin_unlock(&keyring->lock);
 465	return 0;
 466
 467out_put:
 468	fscrypt_put_master_key(mk);
 469	return err;
 470}
 471
 472#define KEY_DEAD	1
 473
 474static int add_existing_master_key(struct fscrypt_master_key *mk,
 475				   struct fscrypt_master_key_secret *secret)
 476{
 477	int err;
 478
 479	/*
 480	 * If the current user is already in ->mk_users, then there's nothing to
 481	 * do.  Otherwise, we need to add the user to ->mk_users.  (Neither is
 482	 * applicable for v1 policy keys, which have NULL ->mk_users.)
 483	 */
 484	if (mk->mk_users) {
 485		struct key *mk_user = find_master_key_user(mk);
 486
 487		if (mk_user != ERR_PTR(-ENOKEY)) {
 488			if (IS_ERR(mk_user))
 489				return PTR_ERR(mk_user);
 490			key_put(mk_user);
 491			return 0;
 492		}
 493		err = add_master_key_user(mk);
 494		if (err)
 495			return err;
 496	}
 497
 498	/* If the key is incompletely removed, make it present again. */
 499	if (!mk->mk_present) {
 500		if (!refcount_inc_not_zero(&mk->mk_active_refs)) {
 501			/*
 502			 * Raced with the last active ref being dropped, so the
 503			 * key has become, or is about to become, "absent".
 504			 * Therefore, we need to allocate a new key struct.
 505			 */
 506			return KEY_DEAD;
 507		}
 508		move_master_key_secret(&mk->mk_secret, secret);
 509		WRITE_ONCE(mk->mk_present, true);
 510	}
 511
 512	return 0;
 513}
 514
 515static int do_add_master_key(struct super_block *sb,
 516			     struct fscrypt_master_key_secret *secret,
 517			     const struct fscrypt_key_specifier *mk_spec)
 518{
 519	static DEFINE_MUTEX(fscrypt_add_key_mutex);
 520	struct fscrypt_master_key *mk;
 521	int err;
 522
 523	mutex_lock(&fscrypt_add_key_mutex); /* serialize find + link */
 524
 525	mk = fscrypt_find_master_key(sb, mk_spec);
 526	if (!mk) {
 527		/* Didn't find the key in ->s_master_keys.  Add it. */
 528		err = allocate_filesystem_keyring(sb);
 529		if (!err)
 530			err = add_new_master_key(sb, secret, mk_spec);
 531	} else {
 532		/*
 533		 * Found the key in ->s_master_keys.  Add the user to ->mk_users
 534		 * if needed, and make the key "present" again if possible.
 535		 */
 536		down_write(&mk->mk_sem);
 537		err = add_existing_master_key(mk, secret);
 538		up_write(&mk->mk_sem);
 539		if (err == KEY_DEAD) {
 540			/*
 541			 * We found a key struct, but it's already been fully
 542			 * removed.  Ignore the old struct and add a new one.
 543			 * fscrypt_add_key_mutex means we don't need to worry
 544			 * about concurrent adds.
 545			 */
 546			err = add_new_master_key(sb, secret, mk_spec);
 547		}
 548		fscrypt_put_master_key(mk);
 549	}
 550	mutex_unlock(&fscrypt_add_key_mutex);
 551	return err;
 552}
 553
 554static int add_master_key(struct super_block *sb,
 555			  struct fscrypt_master_key_secret *secret,
 556			  struct fscrypt_key_specifier *key_spec)
 557{
 558	int err;
 559
 560	if (key_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
 561		u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE];
 562		u8 *kdf_key = secret->bytes;
 563		unsigned int kdf_key_size = secret->size;
 564		u8 keyid_kdf_ctx = HKDF_CONTEXT_KEY_IDENTIFIER_FOR_RAW_KEY;
 565
 566		/*
 567		 * For raw keys, the fscrypt master key is used directly as the
 568		 * fscrypt KDF key.  For hardware-wrapped keys, we have to pass
 569		 * the master key to the hardware to derive the KDF key, which
 570		 * is then only used to derive non-file-contents subkeys.
 571		 */
 572		if (secret->is_hw_wrapped) {
 573			err = fscrypt_derive_sw_secret(sb, secret->bytes,
 574						       secret->size, sw_secret);
 575			if (err)
 576				return err;
 577			kdf_key = sw_secret;
 578			kdf_key_size = sizeof(sw_secret);
 579			/*
 580			 * To avoid weird behavior if someone manages to
 581			 * determine sw_secret and add it as a raw key, ensure
 582			 * that hardware-wrapped keys and raw keys will have
 583			 * different key identifiers by deriving their key
 584			 * identifiers using different KDF contexts.
 585			 */
 586			keyid_kdf_ctx =
 587				HKDF_CONTEXT_KEY_IDENTIFIER_FOR_HW_WRAPPED_KEY;
 588		}
 589		fscrypt_init_hkdf(&secret->hkdf, kdf_key, kdf_key_size);
 590		/*
 591		 * Now that the KDF context is initialized, the raw KDF key is
 592		 * no longer needed.
 593		 */
 594		memzero_explicit(kdf_key, kdf_key_size);
 595
 596		/* Calculate the key identifier */
 597		fscrypt_hkdf_expand(&secret->hkdf, keyid_kdf_ctx, NULL, 0,
 598				    key_spec->u.identifier,
 599				    FSCRYPT_KEY_IDENTIFIER_SIZE);
 600	}
 601	return do_add_master_key(sb, secret, key_spec);
 602}
 603
 604/*
 605 * Validate the size of an fscrypt master key being added.  Note that this is
 606 * just an initial check, as we don't know which ciphers will be used yet.
 607 * There is a stricter size check later when the key is actually used by a file.
 608 */
 609static inline bool fscrypt_valid_key_size(size_t size, u32 add_key_flags)
 610{
 611	u32 max_size = (add_key_flags & FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED) ?
 612		       FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE :
 613		       FSCRYPT_MAX_RAW_KEY_SIZE;
 614
 615	return size >= FSCRYPT_MIN_KEY_SIZE && size <= max_size;
 616}
 617
 618static int fscrypt_provisioning_key_preparse(struct key_preparsed_payload *prep)
 619{
 620	const struct fscrypt_provisioning_key_payload *payload = prep->data;
 621
 622	if (prep->datalen < sizeof(*payload))
 623		return -EINVAL;
 624
 625	if (!fscrypt_valid_key_size(prep->datalen - sizeof(*payload),
 626				    payload->flags))
 627		return -EINVAL;
 628
 629	if (payload->type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
 630	    payload->type != FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER)
 631		return -EINVAL;
 632
 633	if (payload->flags & ~FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED)
 634		return -EINVAL;
 635
 636	prep->payload.data[0] = kmemdup(payload, prep->datalen, GFP_KERNEL);
 637	if (!prep->payload.data[0])
 638		return -ENOMEM;
 639
 640	prep->quotalen = prep->datalen;
 641	return 0;
 642}
 643
 644static void fscrypt_provisioning_key_free_preparse(
 645					struct key_preparsed_payload *prep)
 646{
 647	kfree_sensitive(prep->payload.data[0]);
 648}
 649
 650static void fscrypt_provisioning_key_describe(const struct key *key,
 651					      struct seq_file *m)
 652{
 653	seq_puts(m, key->description);
 654	if (key_is_positive(key)) {
 655		const struct fscrypt_provisioning_key_payload *payload =
 656			key->payload.data[0];
 657
 658		seq_printf(m, ": %u [%u]", key->datalen, payload->type);
 659	}
 660}
 661
 662static void fscrypt_provisioning_key_destroy(struct key *key)
 663{
 664	kfree_sensitive(key->payload.data[0]);
 665}
 666
 667static struct key_type key_type_fscrypt_provisioning = {
 668	.name			= "fscrypt-provisioning",
 669	.preparse		= fscrypt_provisioning_key_preparse,
 670	.free_preparse		= fscrypt_provisioning_key_free_preparse,
 671	.instantiate		= generic_key_instantiate,
 672	.describe		= fscrypt_provisioning_key_describe,
 673	.destroy		= fscrypt_provisioning_key_destroy,
 674};
 675
 676/*
 677 * Retrieve the key from the Linux keyring key specified by 'key_id', and store
 678 * it into 'secret'.
 679 *
 680 * The key must be of type "fscrypt-provisioning" and must have the 'type' and
 681 * 'flags' field of the payload set to the given values, indicating that the key
 682 * is intended for use for the specified purpose.  We don't use the "logon" key
 683 * type because there's no way to completely restrict the use of such keys; they
 684 * can be used by any kernel API that accepts "logon" keys and doesn't require a
 685 * specific service prefix.
 686 *
 687 * The ability to specify the key via Linux keyring key is intended for cases
 688 * where userspace needs to re-add keys after the filesystem is unmounted and
 689 * re-mounted.  Most users should just provide the key directly instead.
 690 */
 691static int get_keyring_key(u32 key_id, u32 type, u32 flags,
 692			   struct fscrypt_master_key_secret *secret)
 693{
 694	key_ref_t ref;
 695	struct key *key;
 696	const struct fscrypt_provisioning_key_payload *payload;
 697	int err;
 698
 699	ref = lookup_user_key(key_id, 0, KEY_NEED_SEARCH);
 700	if (IS_ERR(ref))
 701		return PTR_ERR(ref);
 702	key = key_ref_to_ptr(ref);
 703
 704	if (key->type != &key_type_fscrypt_provisioning)
 705		goto bad_key;
 706	payload = key->payload.data[0];
 707
 708	/*
 709	 * Don't allow fscrypt v1 keys to be used as v2 keys and vice versa.
 710	 * Similarly, don't allow hardware-wrapped keys to be used as
 711	 * non-hardware-wrapped keys and vice versa.
 712	 */
 713	if (payload->type != type || payload->flags != flags)
 714		goto bad_key;
 715
 716	secret->size = key->datalen - sizeof(*payload);
 717	memcpy(secret->bytes, payload->raw, secret->size);
 718	err = 0;
 719	goto out_put;
 720
 721bad_key:
 722	err = -EKEYREJECTED;
 723out_put:
 724	key_ref_put(ref);
 725	return err;
 726}
 727
 728/*
 729 * Add a master encryption key to the filesystem, causing all files which were
 730 * encrypted with it to appear "unlocked" (decrypted) when accessed.
 731 *
 732 * When adding a key for use by v1 encryption policies, this ioctl is
 733 * privileged, and userspace must provide the 'key_descriptor'.
 734 *
 735 * When adding a key for use by v2+ encryption policies, this ioctl is
 736 * unprivileged.  This is needed, in general, to allow non-root users to use
 737 * encryption without encountering the visibility problems of process-subscribed
 738 * keyrings and the inability to properly remove keys.  This works by having
 739 * each key identified by its cryptographically secure hash --- the
 740 * 'key_identifier'.  The cryptographic hash ensures that a malicious user
 741 * cannot add the wrong key for a given identifier.  Furthermore, each added key
 742 * is charged to the appropriate user's quota for the keyrings service, which
 743 * prevents a malicious user from adding too many keys.  Finally, we forbid a
 744 * user from removing a key while other users have added it too, which prevents
 745 * a user who knows another user's key from causing a denial-of-service by
 746 * removing it at an inopportune time.  (We tolerate that a user who knows a key
 747 * can prevent other users from removing it.)
 748 *
 749 * For more details, see the "FS_IOC_ADD_ENCRYPTION_KEY" section of
 750 * Documentation/filesystems/fscrypt.rst.
 751 */
 752int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
 753{
 754	struct super_block *sb = file_inode(filp)->i_sb;
 755	struct fscrypt_add_key_arg __user *uarg = _uarg;
 756	struct fscrypt_add_key_arg arg;
 757	struct fscrypt_master_key_secret secret;
 758	int err;
 759
 760	if (copy_from_user(&arg, uarg, sizeof(arg)))
 761		return -EFAULT;
 762
 763	if (!valid_key_spec(&arg.key_spec))
 764		return -EINVAL;
 765
 766	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
 767		return -EINVAL;
 768
 769	/*
 770	 * Only root can add keys that are identified by an arbitrary descriptor
 771	 * rather than by a cryptographic hash --- since otherwise a malicious
 772	 * user could add the wrong key.
 773	 */
 774	if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
 775	    !capable(CAP_SYS_ADMIN))
 776		return -EACCES;
 777
 778	memset(&secret, 0, sizeof(secret));
 779
 780	if (arg.flags) {
 781		if (arg.flags & ~FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED)
 782			return -EINVAL;
 783		if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER)
 784			return -EINVAL;
 785		secret.is_hw_wrapped = true;
 786	}
 787
 788	if (arg.key_id) {
 789		if (arg.raw_size != 0)
 790			return -EINVAL;
 791		err = get_keyring_key(arg.key_id, arg.key_spec.type, arg.flags,
 792				      &secret);
 793		if (err)
 794			goto out_wipe_secret;
 795	} else {
 796		if (!fscrypt_valid_key_size(arg.raw_size, arg.flags))
 797			return -EINVAL;
 798		secret.size = arg.raw_size;
 799		err = -EFAULT;
 800		if (copy_from_user(secret.bytes, uarg->raw, secret.size))
 801			goto out_wipe_secret;
 802	}
 803
 804	err = add_master_key(sb, &secret, &arg.key_spec);
 805	if (err)
 806		goto out_wipe_secret;
 807
 808	/* Return the key identifier to userspace, if applicable */
 809	err = -EFAULT;
 810	if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER &&
 811	    copy_to_user(uarg->key_spec.u.identifier, arg.key_spec.u.identifier,
 812			 FSCRYPT_KEY_IDENTIFIER_SIZE))
 813		goto out_wipe_secret;
 814	err = 0;
 815out_wipe_secret:
 816	wipe_master_key_secret(&secret);
 817	return err;
 818}
 819EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
 820
 821static void
 822fscrypt_get_test_dummy_secret(struct fscrypt_master_key_secret *secret)
 823{
 824	static u8 test_key[FSCRYPT_MAX_RAW_KEY_SIZE];
 825
 826	get_random_once(test_key, sizeof(test_key));
 827
 828	memset(secret, 0, sizeof(*secret));
 829	secret->size = sizeof(test_key);
 830	memcpy(secret->bytes, test_key, sizeof(test_key));
 831}
 832
 833void fscrypt_get_test_dummy_key_identifier(
 834				u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
 835{
 836	struct fscrypt_master_key_secret secret;
 837
 838	fscrypt_get_test_dummy_secret(&secret);
 839	fscrypt_init_hkdf(&secret.hkdf, secret.bytes, secret.size);
 840	fscrypt_hkdf_expand(&secret.hkdf,
 841			    HKDF_CONTEXT_KEY_IDENTIFIER_FOR_RAW_KEY, NULL, 0,
 842			    key_identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
 843	wipe_master_key_secret(&secret);
 844}
 845
 846/**
 847 * fscrypt_add_test_dummy_key() - add the test dummy encryption key
 848 * @sb: the filesystem instance to add the key to
 849 * @key_spec: the key specifier of the test dummy encryption key
 850 *
 851 * Add the key for the test_dummy_encryption mount option to the filesystem.  To
 852 * prevent misuse of this mount option, a per-boot random key is used instead of
 853 * a hardcoded one.  This makes it so that any encrypted files created using
 854 * this option won't be accessible after a reboot.
 855 *
 856 * Return: 0 on success, -errno on failure
 857 */
 858int fscrypt_add_test_dummy_key(struct super_block *sb,
 859			       struct fscrypt_key_specifier *key_spec)
 860{
 861	struct fscrypt_master_key_secret secret;
 862	int err;
 863
 864	fscrypt_get_test_dummy_secret(&secret);
 865	err = add_master_key(sb, &secret, key_spec);
 866	wipe_master_key_secret(&secret);
 867	return err;
 868}
 869
 870/*
 871 * Verify that the current user has added a master key with the given identifier
 872 * (returns -ENOKEY if not).  This is needed to prevent a user from encrypting
 873 * their files using some other user's key which they don't actually know.
 874 * Cryptographically this isn't much of a problem, but the semantics of this
 875 * would be a bit weird, so it's best to just forbid it.
 876 *
 877 * The system administrator (CAP_FOWNER) can override this, which should be
 878 * enough for any use cases where encryption policies are being set using keys
 879 * that were chosen ahead of time but aren't available at the moment.
 880 *
 881 * Note that the key may have already removed by the time this returns, but
 882 * that's okay; we just care whether the key was there at some point.
 883 *
 884 * Return: 0 if the key is added, -ENOKEY if it isn't, or another -errno code
 885 */
 886int fscrypt_verify_key_added(struct super_block *sb,
 887			     const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE])
 888{
 889	struct fscrypt_key_specifier mk_spec;
 890	struct fscrypt_master_key *mk;
 891	struct key *mk_user;
 892	int err;
 893
 894	mk_spec.type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER;
 895	memcpy(mk_spec.u.identifier, identifier, FSCRYPT_KEY_IDENTIFIER_SIZE);
 896
 897	mk = fscrypt_find_master_key(sb, &mk_spec);
 898	if (!mk) {
 899		err = -ENOKEY;
 900		goto out;
 901	}
 902	down_read(&mk->mk_sem);
 903	mk_user = find_master_key_user(mk);
 904	if (IS_ERR(mk_user)) {
 905		err = PTR_ERR(mk_user);
 906	} else {
 907		key_put(mk_user);
 908		err = 0;
 909	}
 910	up_read(&mk->mk_sem);
 911	fscrypt_put_master_key(mk);
 912out:
 913	if (err == -ENOKEY && capable(CAP_FOWNER))
 914		err = 0;
 915	return err;
 916}
 917
 918/*
 919 * Try to evict the inode's dentries from the dentry cache.  If the inode is a
 920 * directory, then it can have at most one dentry; however, that dentry may be
 921 * pinned by child dentries, so first try to evict the children too.
 922 */
 923static void shrink_dcache_inode(struct inode *inode)
 924{
 925	struct dentry *dentry;
 926
 927	if (S_ISDIR(inode->i_mode)) {
 928		dentry = d_find_any_alias(inode);
 929		if (dentry) {
 930			shrink_dcache_parent(dentry);
 931			dput(dentry);
 932		}
 933	}
 934	d_prune_aliases(inode);
 935}
 936
 937static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk)
 938{
 939	struct fscrypt_inode_info *ci;
 940	struct inode *inode;
 941	struct inode *toput_inode = NULL;
 942
 943	spin_lock(&mk->mk_decrypted_inodes_lock);
 944
 945	list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) {
 946		inode = ci->ci_inode;
 947		spin_lock(&inode->i_lock);
 948		if (inode_state_read(inode) & (I_FREEING | I_WILL_FREE | I_NEW)) {
 949			spin_unlock(&inode->i_lock);
 950			continue;
 951		}
 952		__iget(inode);
 953		spin_unlock(&inode->i_lock);
 954		spin_unlock(&mk->mk_decrypted_inodes_lock);
 955
 956		shrink_dcache_inode(inode);
 957		iput(toput_inode);
 958		toput_inode = inode;
 959
 960		spin_lock(&mk->mk_decrypted_inodes_lock);
 961	}
 962
 963	spin_unlock(&mk->mk_decrypted_inodes_lock);
 964	iput(toput_inode);
 965}
 966
 967static int check_for_busy_inodes(struct super_block *sb,
 968				 struct fscrypt_master_key *mk)
 969{
 970	struct list_head *pos;
 971	size_t busy_count = 0;
 972	unsigned long ino;
 973	char ino_str[50] = "";
 974
 975	spin_lock(&mk->mk_decrypted_inodes_lock);
 976
 977	list_for_each(pos, &mk->mk_decrypted_inodes)
 978		busy_count++;
 979
 980	if (busy_count == 0) {
 981		spin_unlock(&mk->mk_decrypted_inodes_lock);
 982		return 0;
 983	}
 984
 985	{
 986		/* select an example file to show for debugging purposes */
 987		struct inode *inode =
 988			list_first_entry(&mk->mk_decrypted_inodes,
 989					 struct fscrypt_inode_info,
 990					 ci_master_key_link)->ci_inode;
 991		ino = inode->i_ino;
 992	}
 993	spin_unlock(&mk->mk_decrypted_inodes_lock);
 994
 995	/* If the inode is currently being created, ino may still be 0. */
 996	if (ino)
 997		snprintf(ino_str, sizeof(ino_str), ", including ino %lu", ino);
 998
 999	fscrypt_warn(NULL,
1000		     "%s: %zu inode(s) still busy after removing key with %s %*phN%s",
1001		     sb->s_id, busy_count, master_key_spec_type(&mk->mk_spec),
1002		     master_key_spec_len(&mk->mk_spec), (u8 *)&mk->mk_spec.u,
1003		     ino_str);
1004	return -EBUSY;
1005}
1006
1007static int try_to_lock_encrypted_files(struct super_block *sb,
1008				       struct fscrypt_master_key *mk)
1009{
1010	int err1;
1011	int err2;
1012
1013	/*
1014	 * An inode can't be evicted while it is dirty or has dirty pages.
1015	 * Thus, we first have to clean the inodes in ->mk_decrypted_inodes.
1016	 *
1017	 * Just do it the easy way: call sync_filesystem().  It's overkill, but
1018	 * it works, and it's more important to minimize the amount of caches we
1019	 * drop than the amount of data we sync.  Also, unprivileged users can
1020	 * already call sync_filesystem() via sys_syncfs() or sys_sync().
1021	 */
1022	down_read(&sb->s_umount);
1023	err1 = sync_filesystem(sb);
1024	up_read(&sb->s_umount);
1025	/* If a sync error occurs, still try to evict as much as possible. */
1026
1027	/*
1028	 * Inodes are pinned by their dentries, so we have to evict their
1029	 * dentries.  shrink_dcache_sb() would suffice, but would be overkill
1030	 * and inappropriate for use by unprivileged users.  So instead go
1031	 * through the inodes' alias lists and try to evict each dentry.
1032	 */
1033	evict_dentries_for_decrypted_inodes(mk);
1034
1035	/*
1036	 * evict_dentries_for_decrypted_inodes() already iput() each inode in
1037	 * the list; any inodes for which that dropped the last reference will
1038	 * have been evicted due to fscrypt_drop_inode() detecting the key
1039	 * removal and telling the VFS to evict the inode.  So to finish, we
1040	 * just need to check whether any inodes couldn't be evicted.
1041	 */
1042	err2 = check_for_busy_inodes(sb, mk);
1043
1044	return err1 ?: err2;
1045}
1046
1047/*
1048 * Try to remove an fscrypt master encryption key.
1049 *
1050 * FS_IOC_REMOVE_ENCRYPTION_KEY (all_users=false) removes the current user's
1051 * claim to the key, then removes the key itself if no other users have claims.
1052 * FS_IOC_REMOVE_ENCRYPTION_KEY_ALL_USERS (all_users=true) always removes the
1053 * key itself.
1054 *
1055 * To "remove the key itself", first we transition the key to the "incompletely
1056 * removed" state, so that no more inodes can be unlocked with it.  Then we try
1057 * to evict all cached inodes that had been unlocked with the key.
1058 *
1059 * If all inodes were evicted, then we unlink the fscrypt_master_key from the
1060 * keyring.  Otherwise it remains in the keyring in the "incompletely removed"
1061 * state where it tracks the list of remaining inodes.  Userspace can execute
1062 * the ioctl again later to retry eviction, or alternatively can re-add the key.
1063 *
1064 * For more details, see the "Removing keys" section of
1065 * Documentation/filesystems/fscrypt.rst.
1066 */
1067static int do_remove_key(struct file *filp, void __user *_uarg, bool all_users)
1068{
1069	struct super_block *sb = file_inode(filp)->i_sb;
1070	struct fscrypt_remove_key_arg __user *uarg = _uarg;
1071	struct fscrypt_remove_key_arg arg;
1072	struct fscrypt_master_key *mk;
1073	u32 status_flags = 0;
1074	int err;
1075	bool inodes_remain;
1076
1077	if (copy_from_user(&arg, uarg, sizeof(arg)))
1078		return -EFAULT;
1079
1080	if (!valid_key_spec(&arg.key_spec))
1081		return -EINVAL;
1082
1083	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
1084		return -EINVAL;
1085
1086	/*
1087	 * Only root can add and remove keys that are identified by an arbitrary
1088	 * descriptor rather than by a cryptographic hash.
1089	 */
1090	if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
1091	    !capable(CAP_SYS_ADMIN))
1092		return -EACCES;
1093
1094	/* Find the key being removed. */
1095	mk = fscrypt_find_master_key(sb, &arg.key_spec);
1096	if (!mk)
1097		return -ENOKEY;
1098	down_write(&mk->mk_sem);
1099
1100	/* If relevant, remove current user's (or all users) claim to the key */
1101	if (mk->mk_users && mk->mk_users->keys.nr_leaves_on_tree != 0) {
1102		if (all_users)
1103			err = keyring_clear(mk->mk_users);
1104		else
1105			err = remove_master_key_user(mk);
1106		if (err) {
1107			up_write(&mk->mk_sem);
1108			goto out_put_key;
1109		}
1110		if (mk->mk_users->keys.nr_leaves_on_tree != 0) {
1111			/*
1112			 * Other users have still added the key too.  We removed
1113			 * the current user's claim to the key, but we still
1114			 * can't remove the key itself.
1115			 */
1116			status_flags |=
1117				FSCRYPT_KEY_REMOVAL_STATUS_FLAG_OTHER_USERS;
1118			err = 0;
1119			up_write(&mk->mk_sem);
1120			goto out_put_key;
1121		}
1122	}
1123
1124	/* No user claims remaining.  Initiate removal of the key. */
1125	err = -ENOKEY;
1126	if (mk->mk_present) {
1127		fscrypt_initiate_key_removal(sb, mk);
1128		err = 0;
1129	}
1130	inodes_remain = refcount_read(&mk->mk_active_refs) > 0;
1131	up_write(&mk->mk_sem);
1132
1133	if (inodes_remain) {
1134		/* Some inodes still reference this key; try to evict them. */
1135		err = try_to_lock_encrypted_files(sb, mk);
1136		if (err == -EBUSY) {
1137			status_flags |=
1138				FSCRYPT_KEY_REMOVAL_STATUS_FLAG_FILES_BUSY;
1139			err = 0;
1140		}
1141	}
1142	/*
1143	 * We return 0 if we successfully did something: removed a claim to the
1144	 * key, initiated removal of the key, or tried locking the files again.
1145	 * Users need to check the informational status flags if they care
1146	 * whether the key has been fully removed including all files locked.
1147	 */
1148out_put_key:
1149	fscrypt_put_master_key(mk);
1150	if (err == 0)
1151		err = put_user(status_flags, &uarg->removal_status_flags);
1152	return err;
1153}
1154
1155int fscrypt_ioctl_remove_key(struct file *filp, void __user *uarg)
1156{
1157	return do_remove_key(filp, uarg, false);
1158}
1159EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key);
1160
1161int fscrypt_ioctl_remove_key_all_users(struct file *filp, void __user *uarg)
1162{
1163	if (!capable(CAP_SYS_ADMIN))
1164		return -EACCES;
1165	return do_remove_key(filp, uarg, true);
1166}
1167EXPORT_SYMBOL_GPL(fscrypt_ioctl_remove_key_all_users);
1168
1169/*
1170 * Retrieve the status of an fscrypt master encryption key.
1171 *
1172 * We set ->status to indicate whether the key is absent, present, or
1173 * incompletely removed.  (For an explanation of what these statuses mean and
1174 * how they are represented internally, see struct fscrypt_master_key.)  This
1175 * field allows applications to easily determine the status of an encrypted
1176 * directory without using a hack such as trying to open a regular file in it
1177 * (which can confuse the "incompletely removed" status with absent or present).
1178 *
1179 * In addition, for v2 policy keys we allow applications to determine, via
1180 * ->status_flags and ->user_count, whether the key has been added by the
1181 * current user, by other users, or by both.  Most applications should not need
1182 * this, since ordinarily only one user should know a given key.  However, if a
1183 * secret key is shared by multiple users, applications may wish to add an
1184 * already-present key to prevent other users from removing it.  This ioctl can
1185 * be used to check whether that really is the case before the work is done to
1186 * add the key --- which might e.g. require prompting the user for a passphrase.
1187 *
1188 * For more details, see the "FS_IOC_GET_ENCRYPTION_KEY_STATUS" section of
1189 * Documentation/filesystems/fscrypt.rst.
1190 */
1191int fscrypt_ioctl_get_key_status(struct file *filp, void __user *uarg)
1192{
1193	struct super_block *sb = file_inode(filp)->i_sb;
1194	struct fscrypt_get_key_status_arg arg;
1195	struct fscrypt_master_key *mk;
1196	int err;
1197
1198	if (copy_from_user(&arg, uarg, sizeof(arg)))
1199		return -EFAULT;
1200
1201	if (!valid_key_spec(&arg.key_spec))
1202		return -EINVAL;
1203
1204	if (memchr_inv(arg.__reserved, 0, sizeof(arg.__reserved)))
1205		return -EINVAL;
1206
1207	arg.status_flags = 0;
1208	arg.user_count = 0;
1209	memset(arg.__out_reserved, 0, sizeof(arg.__out_reserved));
1210
1211	mk = fscrypt_find_master_key(sb, &arg.key_spec);
1212	if (!mk) {
1213		arg.status = FSCRYPT_KEY_STATUS_ABSENT;
1214		err = 0;
1215		goto out;
1216	}
1217	down_read(&mk->mk_sem);
1218
1219	if (!mk->mk_present) {
1220		arg.status = refcount_read(&mk->mk_active_refs) > 0 ?
1221			FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED :
1222			FSCRYPT_KEY_STATUS_ABSENT /* raced with full removal */;
1223		err = 0;
1224		goto out_release_key;
1225	}
1226
1227	arg.status = FSCRYPT_KEY_STATUS_PRESENT;
1228	if (mk->mk_users) {
1229		struct key *mk_user;
1230
1231		arg.user_count = mk->mk_users->keys.nr_leaves_on_tree;
1232		mk_user = find_master_key_user(mk);
1233		if (!IS_ERR(mk_user)) {
1234			arg.status_flags |=
1235				FSCRYPT_KEY_STATUS_FLAG_ADDED_BY_SELF;
1236			key_put(mk_user);
1237		} else if (mk_user != ERR_PTR(-ENOKEY)) {
1238			err = PTR_ERR(mk_user);
1239			goto out_release_key;
1240		}
1241	}
1242	err = 0;
1243out_release_key:
1244	up_read(&mk->mk_sem);
1245	fscrypt_put_master_key(mk);
1246out:
1247	if (!err && copy_to_user(uarg, &arg, sizeof(arg)))
1248		err = -EFAULT;
1249	return err;
1250}
1251EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_key_status);
1252
1253int __init fscrypt_init_keyring(void)
1254{
1255	int err;
1256
1257	err = register_key_type(&key_type_fscrypt_user);
1258	if (err)
1259		return err;
1260
1261	err = register_key_type(&key_type_fscrypt_provisioning);
1262	if (err)
1263		goto err_unregister_fscrypt_user;
1264
1265	return 0;
1266
1267err_unregister_fscrypt_user:
1268	unregister_key_type(&key_type_fscrypt_user);
1269	return err;
1270}