1 // SPDX-License-Identifier: GPL-2.0
3 * Key setup facility for FS encryption support.
5 * Copyright (C) 2015, Google, Inc.
7 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8 * Heavily modified since then.
11 #include <crypto/skcipher.h>
12 #include <linux/random.h>
14 #include "fscrypt_private.h"
16 struct fscrypt_mode fscrypt_modes[] = {
17 [FSCRYPT_MODE_AES_256_XTS] = {
18 .friendly_name = "AES-256-XTS",
19 .cipher_str = "xts(aes)",
21 .security_strength = 32,
23 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS,
25 [FSCRYPT_MODE_AES_256_CTS] = {
26 .friendly_name = "AES-256-CTS-CBC",
27 .cipher_str = "cts(cbc(aes))",
29 .security_strength = 32,
32 [FSCRYPT_MODE_AES_128_CBC] = {
33 .friendly_name = "AES-128-CBC-ESSIV",
34 .cipher_str = "essiv(cbc(aes),sha256)",
36 .security_strength = 16,
38 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
40 [FSCRYPT_MODE_AES_128_CTS] = {
41 .friendly_name = "AES-128-CTS-CBC",
42 .cipher_str = "cts(cbc(aes))",
44 .security_strength = 16,
47 [FSCRYPT_MODE_SM4_XTS] = {
48 .friendly_name = "SM4-XTS",
49 .cipher_str = "xts(sm4)",
51 .security_strength = 16,
53 .blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS,
55 [FSCRYPT_MODE_SM4_CTS] = {
56 .friendly_name = "SM4-CTS-CBC",
57 .cipher_str = "cts(cbc(sm4))",
59 .security_strength = 16,
62 [FSCRYPT_MODE_ADIANTUM] = {
63 .friendly_name = "Adiantum",
64 .cipher_str = "adiantum(xchacha12,aes)",
66 .security_strength = 32,
68 .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM,
70 [FSCRYPT_MODE_AES_256_HCTR2] = {
71 .friendly_name = "AES-256-HCTR2",
72 .cipher_str = "hctr2(aes)",
74 .security_strength = 32,
79 static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex);
81 static struct fscrypt_mode *
82 select_encryption_mode(const union fscrypt_policy *policy,
83 const struct inode *inode)
85 BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1);
87 if (S_ISREG(inode->i_mode))
88 return &fscrypt_modes[fscrypt_policy_contents_mode(policy)];
90 if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
91 return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)];
93 WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
94 inode->i_ino, (inode->i_mode & S_IFMT));
95 return ERR_PTR(-EINVAL);
98 /* Create a symmetric cipher object for the given encryption mode and key */
99 static struct crypto_skcipher *
100 fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
101 const struct inode *inode)
103 struct crypto_skcipher *tfm;
106 tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
108 if (PTR_ERR(tfm) == -ENOENT) {
110 "Missing crypto API support for %s (API name: \"%s\")",
111 mode->friendly_name, mode->cipher_str);
112 return ERR_PTR(-ENOPKG);
114 fscrypt_err(inode, "Error allocating '%s' transform: %ld",
115 mode->cipher_str, PTR_ERR(tfm));
118 if (!xchg(&mode->logged_cryptoapi_impl, 1)) {
120 * fscrypt performance can vary greatly depending on which
121 * crypto algorithm implementation is used. Help people debug
122 * performance problems by logging the ->cra_driver_name the
123 * first time a mode is used.
125 pr_info("fscrypt: %s using implementation \"%s\"\n",
126 mode->friendly_name, crypto_skcipher_driver_name(tfm));
128 if (WARN_ON_ONCE(crypto_skcipher_ivsize(tfm) != mode->ivsize)) {
132 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
133 err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
140 crypto_free_skcipher(tfm);
145 * Prepare the crypto transform object or blk-crypto key in @prep_key, given the
146 * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption
147 * implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt),
148 * and IV generation method (@ci->ci_policy.flags).
150 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
151 const u8 *raw_key, const struct fscrypt_info *ci)
153 struct crypto_skcipher *tfm;
155 if (fscrypt_using_inline_encryption(ci))
156 return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci);
158 tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode);
162 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().
163 * I.e., here we publish ->tfm with a RELEASE barrier so that
164 * concurrent tasks can ACQUIRE it. Note that this concurrency is only
165 * possible for per-mode keys, not for per-file keys.
167 smp_store_release(&prep_key->tfm, tfm);
171 /* Destroy a crypto transform object and/or blk-crypto key. */
172 void fscrypt_destroy_prepared_key(struct super_block *sb,
173 struct fscrypt_prepared_key *prep_key)
175 crypto_free_skcipher(prep_key->tfm);
176 fscrypt_destroy_inline_crypt_key(sb, prep_key);
177 memzero_explicit(prep_key, sizeof(*prep_key));
180 /* Given a per-file encryption key, set up the file's crypto transform object */
181 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
183 ci->ci_owns_key = true;
184 return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);
187 static int setup_per_mode_enc_key(struct fscrypt_info *ci,
188 struct fscrypt_master_key *mk,
189 struct fscrypt_prepared_key *keys,
190 u8 hkdf_context, bool include_fs_uuid)
192 const struct inode *inode = ci->ci_inode;
193 const struct super_block *sb = inode->i_sb;
194 struct fscrypt_mode *mode = ci->ci_mode;
195 const u8 mode_num = mode - fscrypt_modes;
196 struct fscrypt_prepared_key *prep_key;
197 u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
198 u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)];
199 unsigned int hkdf_infolen = 0;
202 if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX))
205 prep_key = &keys[mode_num];
206 if (fscrypt_is_key_prepared(prep_key, ci)) {
207 ci->ci_enc_key = *prep_key;
211 mutex_lock(&fscrypt_mode_key_setup_mutex);
213 if (fscrypt_is_key_prepared(prep_key, ci))
216 BUILD_BUG_ON(sizeof(mode_num) != 1);
217 BUILD_BUG_ON(sizeof(sb->s_uuid) != 16);
218 BUILD_BUG_ON(sizeof(hkdf_info) != 17);
219 hkdf_info[hkdf_infolen++] = mode_num;
220 if (include_fs_uuid) {
221 memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid,
223 hkdf_infolen += sizeof(sb->s_uuid);
225 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
226 hkdf_context, hkdf_info, hkdf_infolen,
227 mode_key, mode->keysize);
230 err = fscrypt_prepare_key(prep_key, mode_key, ci);
231 memzero_explicit(mode_key, mode->keysize);
235 ci->ci_enc_key = *prep_key;
238 mutex_unlock(&fscrypt_mode_key_setup_mutex);
243 * Derive a SipHash key from the given fscrypt master key and the given
244 * application-specific information string.
246 * Note that the KDF produces a byte array, but the SipHash APIs expect the key
247 * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an
248 * endianness swap in order to get the same results as on little endian CPUs.
250 static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk,
251 u8 context, const u8 *info,
252 unsigned int infolen, siphash_key_t *key)
256 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen,
257 (u8 *)key, sizeof(*key));
261 BUILD_BUG_ON(sizeof(*key) != 16);
262 BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2);
263 le64_to_cpus(&key->key[0]);
264 le64_to_cpus(&key->key[1]);
268 int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
269 const struct fscrypt_master_key *mk)
273 err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY,
274 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
275 &ci->ci_dirhash_key);
278 ci->ci_dirhash_key_initialized = true;
282 void fscrypt_hash_inode_number(struct fscrypt_info *ci,
283 const struct fscrypt_master_key *mk)
285 WARN_ON_ONCE(ci->ci_inode->i_ino == 0);
286 WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized);
288 ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino,
289 &mk->mk_ino_hash_key);
292 static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci,
293 struct fscrypt_master_key *mk)
297 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
298 HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true);
302 /* pairs with smp_store_release() below */
303 if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) {
305 mutex_lock(&fscrypt_mode_key_setup_mutex);
307 if (mk->mk_ino_hash_key_initialized)
310 err = fscrypt_derive_siphash_key(mk,
311 HKDF_CONTEXT_INODE_HASH_KEY,
312 NULL, 0, &mk->mk_ino_hash_key);
315 /* pairs with smp_load_acquire() above */
316 smp_store_release(&mk->mk_ino_hash_key_initialized, true);
318 mutex_unlock(&fscrypt_mode_key_setup_mutex);
324 * New inodes may not have an inode number assigned yet.
325 * Hashing their inode number is delayed until later.
327 if (ci->ci_inode->i_ino)
328 fscrypt_hash_inode_number(ci, mk);
332 static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
333 struct fscrypt_master_key *mk,
334 bool need_dirhash_key)
338 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
340 * DIRECT_KEY: instead of deriving per-file encryption keys, the
341 * per-file nonce will be included in all the IVs. But unlike
342 * v1 policies, for v2 policies in this case we don't encrypt
343 * with the master key directly but rather derive a per-mode
344 * encryption key. This ensures that the master key is
345 * consistently used only for HKDF, avoiding key reuse issues.
347 err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys,
348 HKDF_CONTEXT_DIRECT_KEY, false);
349 } else if (ci->ci_policy.v2.flags &
350 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
352 * IV_INO_LBLK_64: encryption keys are derived from (master_key,
353 * mode_num, filesystem_uuid), and inode number is included in
354 * the IVs. This format is optimized for use with inline
355 * encryption hardware compliant with the UFS standard.
357 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,
358 HKDF_CONTEXT_IV_INO_LBLK_64_KEY,
360 } else if (ci->ci_policy.v2.flags &
361 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
362 err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk);
364 u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
366 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
367 HKDF_CONTEXT_PER_FILE_ENC_KEY,
368 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
369 derived_key, ci->ci_mode->keysize);
373 err = fscrypt_set_per_file_enc_key(ci, derived_key);
374 memzero_explicit(derived_key, ci->ci_mode->keysize);
379 /* Derive a secret dirhash key for directories that need it. */
380 if (need_dirhash_key) {
381 err = fscrypt_derive_dirhash_key(ci, mk);
390 * Check whether the size of the given master key (@mk) is appropriate for the
391 * encryption settings which a particular file will use (@ci).
393 * If the file uses a v1 encryption policy, then the master key must be at least
394 * as long as the derived key, as this is a requirement of the v1 KDF.
396 * Otherwise, the KDF can accept any size key, so we enforce a slightly looser
397 * requirement: we require that the size of the master key be at least the
398 * maximum security strength of any algorithm whose key will be derived from it
399 * (but in practice we only need to consider @ci->ci_mode, since any other
400 * possible subkeys such as DIRHASH and INODE_HASH will never increase the
401 * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be
402 * derived from a 256-bit master key, which is cryptographically sufficient,
403 * rather than requiring a 512-bit master key which is unnecessarily long. (We
404 * still allow 512-bit master keys if the user chooses to use them, though.)
406 static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk,
407 const struct fscrypt_info *ci)
409 unsigned int min_keysize;
411 if (ci->ci_policy.version == FSCRYPT_POLICY_V1)
412 min_keysize = ci->ci_mode->keysize;
414 min_keysize = ci->ci_mode->security_strength;
416 if (mk->mk_secret.size < min_keysize) {
418 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)",
419 master_key_spec_type(&mk->mk_spec),
420 master_key_spec_len(&mk->mk_spec),
421 (u8 *)&mk->mk_spec.u,
422 mk->mk_secret.size, min_keysize);
429 * Find the master key, then set up the inode's actual encryption key.
431 * If the master key is found in the filesystem-level keyring, then it is
432 * returned in *mk_ret with its semaphore read-locked. This is needed to ensure
433 * that only one task links the fscrypt_info into ->mk_decrypted_inodes (as
434 * multiple tasks may race to create an fscrypt_info for the same inode), and to
435 * synchronize the master key being removed with a new inode starting to use it.
437 static int setup_file_encryption_key(struct fscrypt_info *ci,
438 bool need_dirhash_key,
439 struct fscrypt_master_key **mk_ret)
441 struct super_block *sb = ci->ci_inode->i_sb;
442 struct fscrypt_key_specifier mk_spec;
443 struct fscrypt_master_key *mk;
446 err = fscrypt_select_encryption_impl(ci);
450 err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec);
454 mk = fscrypt_find_master_key(sb, &mk_spec);
456 const union fscrypt_policy *dummy_policy =
457 fscrypt_get_dummy_policy(sb);
460 * Add the test_dummy_encryption key on-demand. In principle,
461 * it should be added at mount time. Do it here instead so that
462 * the individual filesystems don't need to worry about adding
463 * this key at mount time and cleaning up on mount failure.
466 fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) {
467 err = fscrypt_add_test_dummy_key(sb, &mk_spec);
470 mk = fscrypt_find_master_key(sb, &mk_spec);
474 if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
478 * As a legacy fallback for v1 policies, search for the key in
479 * the current task's subscribed keyrings too. Don't move this
480 * to before the search of ->s_master_keys, since users
481 * shouldn't be able to override filesystem-level keys.
483 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
485 down_read(&mk->mk_sem);
487 /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
488 if (!is_master_key_secret_present(&mk->mk_secret)) {
490 goto out_release_key;
493 if (!fscrypt_valid_master_key_size(mk, ci)) {
495 goto out_release_key;
498 switch (ci->ci_policy.version) {
499 case FSCRYPT_POLICY_V1:
500 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
502 case FSCRYPT_POLICY_V2:
503 err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
511 goto out_release_key;
517 up_read(&mk->mk_sem);
518 fscrypt_put_master_key(mk);
522 static void put_crypt_info(struct fscrypt_info *ci)
524 struct fscrypt_master_key *mk;
529 if (ci->ci_direct_key)
530 fscrypt_put_direct_key(ci->ci_direct_key);
531 else if (ci->ci_owns_key)
532 fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,
535 mk = ci->ci_master_key;
538 * Remove this inode from the list of inodes that were unlocked
539 * with the master key. In addition, if we're removing the last
540 * inode from a master key struct that already had its secret
541 * removed, then complete the full removal of the struct.
543 spin_lock(&mk->mk_decrypted_inodes_lock);
544 list_del(&ci->ci_master_key_link);
545 spin_unlock(&mk->mk_decrypted_inodes_lock);
546 fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk);
548 memzero_explicit(ci, sizeof(*ci));
549 kmem_cache_free(fscrypt_info_cachep, ci);
553 fscrypt_setup_encryption_info(struct inode *inode,
554 const union fscrypt_policy *policy,
555 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE],
556 bool need_dirhash_key)
558 struct fscrypt_info *crypt_info;
559 struct fscrypt_mode *mode;
560 struct fscrypt_master_key *mk = NULL;
563 res = fscrypt_initialize(inode->i_sb);
567 crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL);
571 crypt_info->ci_inode = inode;
572 crypt_info->ci_policy = *policy;
573 memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
575 mode = select_encryption_mode(&crypt_info->ci_policy, inode);
580 WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
581 crypt_info->ci_mode = mode;
583 res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk);
588 * For existing inodes, multiple tasks may race to set ->i_crypt_info.
589 * So use cmpxchg_release(). This pairs with the smp_load_acquire() in
590 * fscrypt_get_info(). I.e., here we publish ->i_crypt_info with a
591 * RELEASE barrier so that other tasks can ACQUIRE it.
593 if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {
595 * We won the race and set ->i_crypt_info to our crypt_info.
596 * Now link it into the master key's inode list.
599 crypt_info->ci_master_key = mk;
600 refcount_inc(&mk->mk_active_refs);
601 spin_lock(&mk->mk_decrypted_inodes_lock);
602 list_add(&crypt_info->ci_master_key_link,
603 &mk->mk_decrypted_inodes);
604 spin_unlock(&mk->mk_decrypted_inodes_lock);
611 up_read(&mk->mk_sem);
612 fscrypt_put_master_key(mk);
614 put_crypt_info(crypt_info);
619 * fscrypt_get_encryption_info() - set up an inode's encryption key
620 * @inode: the inode to set up the key for. Must be encrypted.
621 * @allow_unsupported: if %true, treat an unsupported encryption policy (or
622 * unrecognized encryption context) the same way as the key
623 * being unavailable, instead of returning an error. Use
624 * %false unless the operation being performed is needed in
625 * order for files (or directories) to be deleted.
627 * Set up ->i_crypt_info, if it hasn't already been done.
629 * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So
630 * generally this shouldn't be called from within a filesystem transaction.
632 * Return: 0 if ->i_crypt_info was set or was already set, *or* if the
633 * encryption key is unavailable. (Use fscrypt_has_encryption_key() to
634 * distinguish these cases.) Also can return another -errno code.
636 int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported)
639 union fscrypt_context ctx;
640 union fscrypt_policy policy;
642 if (fscrypt_has_encryption_key(inode))
645 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
647 if (res == -ERANGE && allow_unsupported)
649 fscrypt_warn(inode, "Error %d getting encryption context", res);
653 res = fscrypt_policy_from_context(&policy, &ctx, res);
655 if (allow_unsupported)
658 "Unrecognized or corrupt encryption context");
662 if (!fscrypt_supported_policy(&policy, inode)) {
663 if (allow_unsupported)
668 res = fscrypt_setup_encryption_info(inode, &policy,
669 fscrypt_context_nonce(&ctx),
670 IS_CASEFOLDED(inode) &&
671 S_ISDIR(inode->i_mode));
673 if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */
681 * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory
682 * @dir: a possibly-encrypted directory
683 * @inode: the new inode. ->i_mode must be set already.
684 * ->i_ino doesn't need to be set yet.
685 * @encrypt_ret: (output) set to %true if the new inode will be encrypted
687 * If the directory is encrypted, set up its ->i_crypt_info in preparation for
688 * encrypting the name of the new file. Also, if the new inode will be
689 * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true.
691 * This isn't %GFP_NOFS-safe, and therefore it should be called before starting
692 * any filesystem transaction to create the inode. For this reason, ->i_ino
693 * isn't required to be set yet, as the filesystem may not have set it yet.
695 * This doesn't persist the new inode's encryption context. That still needs to
696 * be done later by calling fscrypt_set_context().
698 * Return: 0 on success, -ENOKEY if the encryption key is missing, or another
701 int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode,
704 const union fscrypt_policy *policy;
705 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
707 policy = fscrypt_policy_to_inherit(dir);
711 return PTR_ERR(policy);
713 if (WARN_ON_ONCE(inode->i_mode == 0))
717 * Only regular files, directories, and symlinks are encrypted.
718 * Special files like device nodes and named pipes aren't.
720 if (!S_ISREG(inode->i_mode) &&
721 !S_ISDIR(inode->i_mode) &&
722 !S_ISLNK(inode->i_mode))
727 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE);
728 return fscrypt_setup_encryption_info(inode, policy, nonce,
729 IS_CASEFOLDED(dir) &&
730 S_ISDIR(inode->i_mode));
732 EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode);
735 * fscrypt_put_encryption_info() - free most of an inode's fscrypt data
736 * @inode: an inode being evicted
738 * Free the inode's fscrypt_info. Filesystems must call this when the inode is
739 * being evicted. An RCU grace period need not have elapsed yet.
741 void fscrypt_put_encryption_info(struct inode *inode)
743 put_crypt_info(inode->i_crypt_info);
744 inode->i_crypt_info = NULL;
746 EXPORT_SYMBOL(fscrypt_put_encryption_info);
749 * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay
750 * @inode: an inode being freed
752 * Free the inode's cached decrypted symlink target, if any. Filesystems must
753 * call this after an RCU grace period, just before they free the inode.
755 void fscrypt_free_inode(struct inode *inode)
757 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
758 kfree(inode->i_link);
759 inode->i_link = NULL;
762 EXPORT_SYMBOL(fscrypt_free_inode);
765 * fscrypt_drop_inode() - check whether the inode's master key has been removed
766 * @inode: an inode being considered for eviction
768 * Filesystems supporting fscrypt must call this from their ->drop_inode()
769 * method so that encrypted inodes are evicted as soon as they're no longer in
770 * use and their master key has been removed.
772 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0
774 int fscrypt_drop_inode(struct inode *inode)
776 const struct fscrypt_info *ci = fscrypt_get_info(inode);
779 * If ci is NULL, then the inode doesn't have an encryption key set up
780 * so it's irrelevant. If ci_master_key is NULL, then the master key
781 * was provided via the legacy mechanism of the process-subscribed
782 * keyrings, so we don't know whether it's been removed or not.
784 if (!ci || !ci->ci_master_key)
788 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes
789 * protected by the key were cleaned by sync_filesystem(). But if
790 * userspace is still using the files, inodes can be dirtied between
791 * then and now. We mustn't lose any writes, so skip dirty inodes here.
793 if (inode->i_state & I_DIRTY_ALL)
797 * Note: since we aren't holding the key semaphore, the result here can
798 * immediately become outdated. But there's no correctness problem with
799 * unnecessarily evicting. Nor is there a correctness problem with not
800 * evicting while iput() is racing with the key being removed, since
801 * then the thread removing the key will either evict the inode itself
802 * or will correctly detect that it wasn't evicted due to the race.
804 return !is_master_key_secret_present(&ci->ci_master_key->mk_secret);
806 EXPORT_SYMBOL_GPL(fscrypt_drop_inode);