fs/crypto/keyinfo.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * key management facility for FS encryption support.
   4  *
   5  * Copyright (C) 2015, Google, Inc.
   6  *
   7  * This contains encryption key functions.
   8  *
   9  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
  10  */
  11
  12 #include <keys/user-type.h>
  13 #include <linux/hashtable.h>
  14 #include <linux/scatterlist.h>
  15 #include <crypto/aes.h>
  16 #include <crypto/algapi.h>
  17 #include <crypto/sha.h>
  18 #include <crypto/skcipher.h>
  19 #include "fscrypt_private.h"
  20
  21 static struct crypto_shash *essiv_hash_tfm;
  22
  23 /* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */
  24 static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */
  25 static DEFINE_SPINLOCK(fscrypt_master_keys_lock);
  26
  27 /*
  28  * Key derivation function.  This generates the derived key by encrypting the
  29  * master key with AES-128-ECB using the inode's nonce as the AES key.
  30  *
  31  * The master key must be at least as long as the derived key.  If the master
  32  * key is longer, then only the first 'derived_keysize' bytes are used.
  33  */
  34 static int derive_key_aes(const u8 *master_key,
  35                           const struct fscrypt_context *ctx,
  36                           u8 *derived_key, unsigned int derived_keysize)
  37 {
  38         int res = 0;
  39         struct skcipher_request *req = NULL;
  40         DECLARE_CRYPTO_WAIT(wait);
  41         struct scatterlist src_sg, dst_sg;
  42         struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
  43
  44         if (IS_ERR(tfm)) {
  45                 res = PTR_ERR(tfm);
  46                 tfm = NULL;
  47                 goto out;
  48         }
  49         crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
  50         req = skcipher_request_alloc(tfm, GFP_NOFS);
  51         if (!req) {
  52                 res = -ENOMEM;
  53                 goto out;
  54         }
  55         skcipher_request_set_callback(req,
  56                         CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  57                         crypto_req_done, &wait);
  58         res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce));
  59         if (res < 0)
  60                 goto out;
  61
  62         sg_init_one(&src_sg, master_key, derived_keysize);
  63         sg_init_one(&dst_sg, derived_key, derived_keysize);
  64         skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
  65                                    NULL);
  66         res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
  67 out:
  68         skcipher_request_free(req);
  69         crypto_free_skcipher(tfm);
  70         return res;
  71 }
  72
  73 /*
  74  * Search the current task's subscribed keyrings for a "logon" key with
  75  * description prefix:descriptor, and if found acquire a read lock on it and
  76  * return a pointer to its validated payload in *payload_ret.
  77  */
  78 static struct key *
  79 find_and_lock_process_key(const char *prefix,
  80                           const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE],
  81                           unsigned int min_keysize,
  82                           const struct fscrypt_key **payload_ret)
  83 {
  84         char *description;
  85         struct key *key;
  86         const struct user_key_payload *ukp;
  87         const struct fscrypt_key *payload;
  88
  89         description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
  90                                 FS_KEY_DESCRIPTOR_SIZE, descriptor);
  91         if (!description)
  92                 return ERR_PTR(-ENOMEM);
  93
  94         key = request_key(&key_type_logon, description, NULL);
  95         kfree(description);
  96         if (IS_ERR(key))
  97                 return key;
  98
  99         down_read(&key->sem);
 100         ukp = user_key_payload_locked(key);
 101
 102         if (!ukp) /* was the key revoked before we acquired its semaphore? */
 103                 goto invalid;
 104
 105         payload = (const struct fscrypt_key *)ukp->data;
 106
 107         if (ukp->datalen != sizeof(struct fscrypt_key) ||
 108             payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) {
 109                 fscrypt_warn(NULL,
 110                              "key with description '%s' has invalid payload",
 111                              key->description);
 112                 goto invalid;
 113         }
 114
 115         if (payload->size < min_keysize) {
 116                 fscrypt_warn(NULL,
 117                              "key with description '%s' is too short (got %u bytes, need %u+ bytes)",
 118                              key->description, payload->size, min_keysize);
 119                 goto invalid;
 120         }
 121
 122         *payload_ret = payload;
 123         return key;
 124
 125 invalid:
 126         up_read(&key->sem);
 127         key_put(key);
 128         return ERR_PTR(-ENOKEY);
 129 }
 130
 131 static struct fscrypt_mode available_modes[] = {
 132         [FS_ENCRYPTION_MODE_AES_256_XTS] = {
 133                 .friendly_name = "AES-256-XTS",
 134                 .cipher_str = "xts(aes)",
 135                 .keysize = 64,
 136                 .ivsize = 16,
 137         },
 138         [FS_ENCRYPTION_MODE_AES_256_CTS] = {
 139                 .friendly_name = "AES-256-CTS-CBC",
 140                 .cipher_str = "cts(cbc(aes))",
 141                 .keysize = 32,
 142                 .ivsize = 16,
 143         },
 144         [FS_ENCRYPTION_MODE_AES_128_CBC] = {
 145                 .friendly_name = "AES-128-CBC",
 146                 .cipher_str = "cbc(aes)",
 147                 .keysize = 16,
 148                 .ivsize = 16,
 149                 .needs_essiv = true,
 150         },
 151         [FS_ENCRYPTION_MODE_AES_128_CTS] = {
 152                 .friendly_name = "AES-128-CTS-CBC",
 153                 .cipher_str = "cts(cbc(aes))",
 154                 .keysize = 16,
 155                 .ivsize = 16,
 156         },
 157         [FS_ENCRYPTION_MODE_ADIANTUM] = {
 158                 .friendly_name = "Adiantum",
 159                 .cipher_str = "adiantum(xchacha12,aes)",
 160                 .keysize = 32,
 161                 .ivsize = 32,
 162         },
 163 };
 164
 165 static struct fscrypt_mode *
 166 select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
 167 {
 168         if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
 169                 fscrypt_warn(inode->i_sb,
 170                              "inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)",
 171                              inode->i_ino, ci->ci_data_mode,
 172                              ci->ci_filename_mode);
 173                 return ERR_PTR(-EINVAL);
 174         }
 175
 176         if (S_ISREG(inode->i_mode))
 177                 return &available_modes[ci->ci_data_mode];
 178
 179         if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
 180                 return &available_modes[ci->ci_filename_mode];
 181
 182         WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
 183                   inode->i_ino, (inode->i_mode & S_IFMT));
 184         return ERR_PTR(-EINVAL);
 185 }
 186
 187 /* Find the master key, then derive the inode's actual encryption key */
 188 static int find_and_derive_key(const struct inode *inode,
 189                                const struct fscrypt_context *ctx,
 190                                u8 *derived_key, const struct fscrypt_mode *mode)
 191 {
 192         struct key *key;
 193         const struct fscrypt_key *payload;
 194         int err;
 195
 196         key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
 197                                         ctx->master_key_descriptor,
 198                                         mode->keysize, &payload);
 199         if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
 200                 key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
 201                                                 ctx->master_key_descriptor,
 202                                                 mode->keysize, &payload);
 203         }
 204         if (IS_ERR(key))
 205                 return PTR_ERR(key);
 206
 207         if (ctx->flags & FS_POLICY_FLAG_DIRECT_KEY) {
 208                 if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
 209                         fscrypt_warn(inode->i_sb,
 210                                      "direct key mode not allowed with %s",
 211                                      mode->friendly_name);
 212                         err = -EINVAL;
 213                 } else if (ctx->contents_encryption_mode !=
 214                            ctx->filenames_encryption_mode) {
 215                         fscrypt_warn(inode->i_sb,
 216                                      "direct key mode not allowed with different contents and filenames modes");
 217                         err = -EINVAL;
 218                 } else {
 219                         memcpy(derived_key, payload->raw, mode->keysize);
 220                         err = 0;
 221                 }
 222         } else {
 223                 err = derive_key_aes(payload->raw, ctx, derived_key,
 224                                      mode->keysize);
 225         }
 226         up_read(&key->sem);
 227         key_put(key);
 228         return err;
 229 }
 230
 231 /* Allocate and key a symmetric cipher object for the given encryption mode */
 232 static struct crypto_skcipher *
 233 allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
 234                            const struct inode *inode)
 235 {
 236         struct crypto_skcipher *tfm;
 237         int err;
 238
 239         tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
 240         if (IS_ERR(tfm)) {
 241                 fscrypt_warn(inode->i_sb,
 242                              "error allocating '%s' transform for inode %lu: %ld",
 243                              mode->cipher_str, inode->i_ino, PTR_ERR(tfm));
 244                 return tfm;
 245         }
 246         if (unlikely(!mode->logged_impl_name)) {
 247                 /*
 248                  * fscrypt performance can vary greatly depending on which
 249                  * crypto algorithm implementation is used.  Help people debug
 250                  * performance problems by logging the ->cra_driver_name the
 251                  * first time a mode is used.  Note that multiple threads can
 252                  * race here, but it doesn't really matter.
 253                  */
 254                 mode->logged_impl_name = true;
 255                 pr_info("fscrypt: %s using implementation \"%s\"\n",
 256                         mode->friendly_name,
 257                         crypto_skcipher_alg(tfm)->base.cra_driver_name);
 258         }
 259         crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
 260         err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
 261         if (err)
 262                 goto err_free_tfm;
 263
 264         return tfm;
 265
 266 err_free_tfm:
 267         crypto_free_skcipher(tfm);
 268         return ERR_PTR(err);
 269 }
 270
 271 /* Master key referenced by FS_POLICY_FLAG_DIRECT_KEY policy */
 272 struct fscrypt_master_key {
 273         struct hlist_node mk_node;
 274         refcount_t mk_refcount;
 275         const struct fscrypt_mode *mk_mode;
 276         struct crypto_skcipher *mk_ctfm;
 277         u8 mk_descriptor[FS_KEY_DESCRIPTOR_SIZE];
 278         u8 mk_raw[FS_MAX_KEY_SIZE];
 279 };
 280
 281 static void free_master_key(struct fscrypt_master_key *mk)
 282 {
 283         if (mk) {
 284                 crypto_free_skcipher(mk->mk_ctfm);
 285                 kzfree(mk);
 286         }
 287 }
 288
 289 static void put_master_key(struct fscrypt_master_key *mk)
 290 {
 291         if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock))
 292                 return;
 293         hash_del(&mk->mk_node);
 294         spin_unlock(&fscrypt_master_keys_lock);
 295
 296         free_master_key(mk);
 297 }
 298
 299 /*
 300  * Find/insert the given master key into the fscrypt_master_keys table.  If
 301  * found, it is returned with elevated refcount, and 'to_insert' is freed if
 302  * non-NULL.  If not found, 'to_insert' is inserted and returned if it's
 303  * non-NULL; otherwise NULL is returned.
 304  */
 305 static struct fscrypt_master_key *
 306 find_or_insert_master_key(struct fscrypt_master_key *to_insert,
 307                           const u8 *raw_key, const struct fscrypt_mode *mode,
 308                           const struct fscrypt_info *ci)
 309 {
 310         unsigned long hash_key;
 311         struct fscrypt_master_key *mk;
 312
 313         /*
 314          * Careful: to avoid potentially leaking secret key bytes via timing
 315          * information, we must key the hash table by descriptor rather than by
 316          * raw key, and use crypto_memneq() when comparing raw keys.
 317          */
 318
 319         BUILD_BUG_ON(sizeof(hash_key) > FS_KEY_DESCRIPTOR_SIZE);
 320         memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
 321
 322         spin_lock(&fscrypt_master_keys_lock);
 323         hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) {
 324                 if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor,
 325                            FS_KEY_DESCRIPTOR_SIZE) != 0)
 326                         continue;
 327                 if (mode != mk->mk_mode)
 328                         continue;
 329                 if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize))
 330                         continue;
 331                 /* using existing tfm with same (descriptor, mode, raw_key) */
 332                 refcount_inc(&mk->mk_refcount);
 333                 spin_unlock(&fscrypt_master_keys_lock);
 334                 free_master_key(to_insert);
 335                 return mk;
 336         }
 337         if (to_insert)
 338                 hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key);
 339         spin_unlock(&fscrypt_master_keys_lock);
 340         return to_insert;
 341 }
 342
 343 /* Prepare to encrypt directly using the master key in the given mode */
 344 static struct fscrypt_master_key *
 345 fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
 346                        const u8 *raw_key, const struct inode *inode)
 347 {
 348         struct fscrypt_master_key *mk;
 349         int err;
 350
 351         /* Is there already a tfm for this key? */
 352         mk = find_or_insert_master_key(NULL, raw_key, mode, ci);
 353         if (mk)
 354                 return mk;
 355
 356         /* Nope, allocate one. */
 357         mk = kzalloc(sizeof(*mk), GFP_NOFS);
 358         if (!mk)
 359                 return ERR_PTR(-ENOMEM);
 360         refcount_set(&mk->mk_refcount, 1);
 361         mk->mk_mode = mode;
 362         mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
 363         if (IS_ERR(mk->mk_ctfm)) {
 364                 err = PTR_ERR(mk->mk_ctfm);
 365                 mk->mk_ctfm = NULL;
 366                 goto err_free_mk;
 367         }
 368         memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor,
 369                FS_KEY_DESCRIPTOR_SIZE);
 370         memcpy(mk->mk_raw, raw_key, mode->keysize);
 371
 372         return find_or_insert_master_key(mk, raw_key, mode, ci);
 373
 374 err_free_mk:
 375         free_master_key(mk);
 376         return ERR_PTR(err);
 377 }
 378
 379 static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
 380 {
 381         struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
 382
 383         /* init hash transform on demand */
 384         if (unlikely(!tfm)) {
 385                 struct crypto_shash *prev_tfm;
 386
 387                 tfm = crypto_alloc_shash("sha256", 0, 0);
 388                 if (IS_ERR(tfm)) {
 389                         fscrypt_warn(NULL,
 390                                      "error allocating SHA-256 transform: %ld",
 391                                      PTR_ERR(tfm));
 392                         return PTR_ERR(tfm);
 393                 }
 394                 prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
 395                 if (prev_tfm) {
 396                         crypto_free_shash(tfm);
 397                         tfm = prev_tfm;
 398                 }
 399         }
 400
 401         {
 402                 SHASH_DESC_ON_STACK(desc, tfm);
 403                 desc->tfm = tfm;
 404
 405                 return crypto_shash_digest(desc, key, keysize, salt);
 406         }
 407 }
 408
 409 static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
 410                                 int keysize)
 411 {
 412         int err;
 413         struct crypto_cipher *essiv_tfm;
 414         u8 salt[SHA256_DIGEST_SIZE];
 415
 416         essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
 417         if (IS_ERR(essiv_tfm))
 418                 return PTR_ERR(essiv_tfm);
 419
 420         ci->ci_essiv_tfm = essiv_tfm;
 421
 422         err = derive_essiv_salt(raw_key, keysize, salt);
 423         if (err)
 424                 goto out;
 425
 426         /*
 427          * Using SHA256 to derive the salt/key will result in AES-256 being
 428          * used for IV generation. File contents encryption will still use the
 429          * configured keysize (AES-128) nevertheless.
 430          */
 431         err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
 432         if (err)
 433                 goto out;
 434
 435 out:
 436         memzero_explicit(salt, sizeof(salt));
 437         return err;
 438 }
 439
 440 void __exit fscrypt_essiv_cleanup(void)
 441 {
 442         crypto_free_shash(essiv_hash_tfm);
 443 }
 444
 445 /*
 446  * Given the encryption mode and key (normally the derived key, but for
 447  * FS_POLICY_FLAG_DIRECT_KEY mode it's the master key), set up the inode's
 448  * symmetric cipher transform object(s).
 449  */
 450 static int setup_crypto_transform(struct fscrypt_info *ci,
 451                                   struct fscrypt_mode *mode,
 452                                   const u8 *raw_key, const struct inode *inode)
 453 {
 454         struct fscrypt_master_key *mk;
 455         struct crypto_skcipher *ctfm;
 456         int err;
 457
 458         if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) {
 459                 mk = fscrypt_get_master_key(ci, mode, raw_key, inode);
 460                 if (IS_ERR(mk))
 461                         return PTR_ERR(mk);
 462                 ctfm = mk->mk_ctfm;
 463         } else {
 464                 mk = NULL;
 465                 ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
 466                 if (IS_ERR(ctfm))
 467                         return PTR_ERR(ctfm);
 468         }
 469         ci->ci_master_key = mk;
 470         ci->ci_ctfm = ctfm;
 471
 472         if (mode->needs_essiv) {
 473                 /* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
 474                 WARN_ON(mode->ivsize != AES_BLOCK_SIZE);
 475                 WARN_ON(ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY);
 476
 477                 err = init_essiv_generator(ci, raw_key, mode->keysize);
 478                 if (err) {
 479                         fscrypt_warn(inode->i_sb,
 480                                      "error initializing ESSIV generator for inode %lu: %d",
 481                                      inode->i_ino, err);
 482                         return err;
 483                 }
 484         }
 485         return 0;
 486 }
 487
 488 static void put_crypt_info(struct fscrypt_info *ci)
 489 {
 490         if (!ci)
 491                 return;
 492
 493         if (ci->ci_master_key) {
 494                 put_master_key(ci->ci_master_key);
 495         } else {
 496                 crypto_free_skcipher(ci->ci_ctfm);
 497                 crypto_free_cipher(ci->ci_essiv_tfm);
 498         }
 499         kmem_cache_free(fscrypt_info_cachep, ci);
 500 }
 501
 502 int fscrypt_get_encryption_info(struct inode *inode)
 503 {
 504         struct fscrypt_info *crypt_info;
 505         struct fscrypt_context ctx;
 506         struct fscrypt_mode *mode;
 507         u8 *raw_key = NULL;
 508         int res;
 509
 510         if (fscrypt_has_encryption_key(inode))
 511                 return 0;
 512
 513         res = fscrypt_initialize(inode->i_sb->s_cop->flags);
 514         if (res)
 515                 return res;
 516
 517         res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
 518         if (res < 0) {
 519                 if (!fscrypt_dummy_context_enabled(inode) ||
 520                     IS_ENCRYPTED(inode))
 521                         return res;
 522                 /* Fake up a context for an unencrypted directory */
 523                 memset(&ctx, 0, sizeof(ctx));
 524                 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
 525                 ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
 526                 ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
 527                 memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
 528         } else if (res != sizeof(ctx)) {
 529                 return -EINVAL;
 530         }
 531
 532         if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
 533                 return -EINVAL;
 534
 535         if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
 536                 return -EINVAL;
 537
 538         crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
 539         if (!crypt_info)
 540                 return -ENOMEM;
 541
 542         crypt_info->ci_flags = ctx.flags;
 543         crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 544         crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
 545         memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
 546                FS_KEY_DESCRIPTOR_SIZE);
 547         memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
 548
 549         mode = select_encryption_mode(crypt_info, inode);
 550         if (IS_ERR(mode)) {
 551                 res = PTR_ERR(mode);
 552                 goto out;
 553         }
 554         WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
 555         crypt_info->ci_mode = mode;
 556
 557         /*
 558          * This cannot be a stack buffer because it may be passed to the
 559          * scatterlist crypto API as part of key derivation.
 560          */
 561         res = -ENOMEM;
 562         raw_key = kmalloc(mode->keysize, GFP_NOFS);
 563         if (!raw_key)
 564                 goto out;
 565
 566         res = find_and_derive_key(inode, &ctx, raw_key, mode);
 567         if (res)
 568                 goto out;
 569
 570         res = setup_crypto_transform(crypt_info, mode, raw_key, inode);
 571         if (res)
 572                 goto out;
 573
 574         if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL)
 575                 crypt_info = NULL;
 576 out:
 577         if (res == -ENOKEY)
 578                 res = 0;
 579         put_crypt_info(crypt_info);
 580         kzfree(raw_key);
 581         return res;
 582 }
 583 EXPORT_SYMBOL(fscrypt_get_encryption_info);
 584
 585 /**
 586  * fscrypt_put_encryption_info - free most of an inode's fscrypt data
 587  *
 588  * Free the inode's fscrypt_info.  Filesystems must call this when the inode is
 589  * being evicted.  An RCU grace period need not have elapsed yet.
 590  */
 591 void fscrypt_put_encryption_info(struct inode *inode)
 592 {
 593         put_crypt_info(inode->i_crypt_info);
 594         inode->i_crypt_info = NULL;
 595 }
 596 EXPORT_SYMBOL(fscrypt_put_encryption_info);
 597
 598 /**
 599  * fscrypt_free_inode - free an inode's fscrypt data requiring RCU delay
 600  *
 601  * Free the inode's cached decrypted symlink target, if any.  Filesystems must
 602  * call this after an RCU grace period, just before they free the inode.
 603  */
 604 void fscrypt_free_inode(struct inode *inode)
 605 {
 606         if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
 607                 kfree(inode->i_link);
 608                 inode->i_link = NULL;
 609         }
 610 }
 611 EXPORT_SYMBOL(fscrypt_free_inode);