1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * This contains functions for filename crypto management 4 * 5 * Copyright (C) 2015, Google, Inc. 6 * Copyright (C) 2015, Motorola Mobility 7 * 8 * Written by Uday Savagaonkar, 2014. 9 * Modified by Jaegeuk Kim, 2015. 10 * 11 * This has not yet undergone a rigorous security audit. 12 */ 13 14 #include <linux/namei.h> 15 #include <linux/scatterlist.h> 16 #include <crypto/hash.h> 17 #include <crypto/sha2.h> 18 #include <crypto/skcipher.h> 19 #include "fscrypt_private.h" 20 21 /* 22 * The minimum message length (input and output length), in bytes, for all 23 * filenames encryption modes. Filenames shorter than this will be zero-padded 24 * before being encrypted. 25 */ 26 #define FSCRYPT_FNAME_MIN_MSG_LEN 16 27 28 /* 29 * struct fscrypt_nokey_name - identifier for directory entry when key is absent 30 * 31 * When userspace lists an encrypted directory without access to the key, the 32 * filesystem must present a unique "no-key name" for each filename that allows 33 * it to find the directory entry again if requested. Naively, that would just 34 * mean using the ciphertext filenames. However, since the ciphertext filenames 35 * can contain illegal characters ('\0' and '/'), they must be encoded in some 36 * way. We use base64url. But that can cause names to exceed NAME_MAX (255 37 * bytes), so we also need to use a strong hash to abbreviate long names. 38 * 39 * The filesystem may also need another kind of hash, the "dirhash", to quickly 40 * find the directory entry. Since filesystems normally compute the dirhash 41 * over the on-disk filename (i.e. the ciphertext), it's not computable from 42 * no-key names that abbreviate the ciphertext using the strong hash to fit in 43 * NAME_MAX. It's also not computable if it's a keyed hash taken over the 44 * plaintext (but it may still be available in the on-disk directory entry); 45 * casefolded directories use this type of dirhash. At least in these cases, 46 * each no-key name must include the name's dirhash too. 47 * 48 * To meet all these requirements, we base64url-encode the following 49 * variable-length structure. It contains the dirhash, or 0's if the filesystem 50 * didn't provide one; up to 149 bytes of the ciphertext name; and for 51 * ciphertexts longer than 149 bytes, also the SHA-256 of the remaining bytes. 52 * 53 * This ensures that each no-key name contains everything needed to find the 54 * directory entry again, contains only legal characters, doesn't exceed 55 * NAME_MAX, is unambiguous unless there's a SHA-256 collision, and that we only 56 * take the performance hit of SHA-256 on very long filenames (which are rare). 57 */ 58 struct fscrypt_nokey_name { 59 u32 dirhash[2]; 60 u8 bytes[149]; 61 u8 sha256[SHA256_DIGEST_SIZE]; 62 }; /* 189 bytes => 252 bytes base64url-encoded, which is <= NAME_MAX (255) */ 63 64 /* 65 * Decoded size of max-size no-key name, i.e. a name that was abbreviated using 66 * the strong hash and thus includes the 'sha256' field. This isn't simply 67 * sizeof(struct fscrypt_nokey_name), as the padding at the end isn't included. 68 */ 69 #define FSCRYPT_NOKEY_NAME_MAX offsetofend(struct fscrypt_nokey_name, sha256) 70 71 /* Encoded size of max-size no-key name */ 72 #define FSCRYPT_NOKEY_NAME_MAX_ENCODED \ 73 FSCRYPT_BASE64URL_CHARS(FSCRYPT_NOKEY_NAME_MAX) 74 75 static inline bool fscrypt_is_dot_dotdot(const struct qstr *str) 76 { 77 if (str->len == 1 && str->name[0] == '.') 78 return true; 79 80 if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.') 81 return true; 82 83 return false; 84 } 85 86 /** 87 * fscrypt_fname_encrypt() - encrypt a filename 88 * @inode: inode of the parent directory (for regular filenames) 89 * or of the symlink (for symlink targets) 90 * @iname: the filename to encrypt 91 * @out: (output) the encrypted filename 92 * @olen: size of the encrypted filename. It must be at least @iname->len. 93 * Any extra space is filled with NUL padding before encryption. 94 * 95 * Return: 0 on success, -errno on failure 96 */ 97 int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname, 98 u8 *out, unsigned int olen) 99 { 100 struct skcipher_request *req = NULL; 101 DECLARE_CRYPTO_WAIT(wait); 102 const struct fscrypt_info *ci = inode->i_crypt_info; 103 struct crypto_skcipher *tfm = ci->ci_enc_key.tfm; 104 union fscrypt_iv iv; 105 struct scatterlist sg; 106 int res; 107 108 /* 109 * Copy the filename to the output buffer for encrypting in-place and 110 * pad it with the needed number of NUL bytes. 111 */ 112 if (WARN_ON(olen < iname->len)) 113 return -ENOBUFS; 114 memcpy(out, iname->name, iname->len); 115 memset(out + iname->len, 0, olen - iname->len); 116 117 /* Initialize the IV */ 118 fscrypt_generate_iv(&iv, 0, ci); 119 120 /* Set up the encryption request */ 121 req = skcipher_request_alloc(tfm, GFP_NOFS); 122 if (!req) 123 return -ENOMEM; 124 skcipher_request_set_callback(req, 125 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, 126 crypto_req_done, &wait); 127 sg_init_one(&sg, out, olen); 128 skcipher_request_set_crypt(req, &sg, &sg, olen, &iv); 129 130 /* Do the encryption */ 131 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait); 132 skcipher_request_free(req); 133 if (res < 0) { 134 fscrypt_err(inode, "Filename encryption failed: %d", res); 135 return res; 136 } 137 138 return 0; 139 } 140 141 /** 142 * fname_decrypt() - decrypt a filename 143 * @inode: inode of the parent directory (for regular filenames) 144 * or of the symlink (for symlink targets) 145 * @iname: the encrypted filename to decrypt 146 * @oname: (output) the decrypted filename. The caller must have allocated 147 * enough space for this, e.g. using fscrypt_fname_alloc_buffer(). 148 * 149 * Return: 0 on success, -errno on failure 150 */ 151 static int fname_decrypt(const struct inode *inode, 152 const struct fscrypt_str *iname, 153 struct fscrypt_str *oname) 154 { 155 struct skcipher_request *req = NULL; 156 DECLARE_CRYPTO_WAIT(wait); 157 struct scatterlist src_sg, dst_sg; 158 const struct fscrypt_info *ci = inode->i_crypt_info; 159 struct crypto_skcipher *tfm = ci->ci_enc_key.tfm; 160 union fscrypt_iv iv; 161 int res; 162 163 /* Allocate request */ 164 req = skcipher_request_alloc(tfm, GFP_NOFS); 165 if (!req) 166 return -ENOMEM; 167 skcipher_request_set_callback(req, 168 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, 169 crypto_req_done, &wait); 170 171 /* Initialize IV */ 172 fscrypt_generate_iv(&iv, 0, ci); 173 174 /* Create decryption request */ 175 sg_init_one(&src_sg, iname->name, iname->len); 176 sg_init_one(&dst_sg, oname->name, oname->len); 177 skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, &iv); 178 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait); 179 skcipher_request_free(req); 180 if (res < 0) { 181 fscrypt_err(inode, "Filename decryption failed: %d", res); 182 return res; 183 } 184 185 oname->len = strnlen(oname->name, iname->len); 186 return 0; 187 } 188 189 static const char base64url_table[65] = 190 "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"; 191 192 #define FSCRYPT_BASE64URL_CHARS(nbytes) DIV_ROUND_UP((nbytes) * 4, 3) 193 194 /** 195 * fscrypt_base64url_encode() - base64url-encode some binary data 196 * @src: the binary data to encode 197 * @srclen: the length of @src in bytes 198 * @dst: (output) the base64url-encoded string. Not NUL-terminated. 199 * 200 * Encodes data using base64url encoding, i.e. the "Base 64 Encoding with URL 201 * and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't used, 202 * as it's unneeded and not required by the RFC. base64url is used instead of 203 * base64 to avoid the '/' character, which isn't allowed in filenames. 204 * 205 * Return: the length of the resulting base64url-encoded string in bytes. 206 * This will be equal to FSCRYPT_BASE64URL_CHARS(srclen). 207 */ 208 static int fscrypt_base64url_encode(const u8 *src, int srclen, char *dst) 209 { 210 u32 ac = 0; 211 int bits = 0; 212 int i; 213 char *cp = dst; 214 215 for (i = 0; i < srclen; i++) { 216 ac = (ac << 8) | src[i]; 217 bits += 8; 218 do { 219 bits -= 6; 220 *cp++ = base64url_table[(ac >> bits) & 0x3f]; 221 } while (bits >= 6); 222 } 223 if (bits) 224 *cp++ = base64url_table[(ac << (6 - bits)) & 0x3f]; 225 return cp - dst; 226 } 227 228 /** 229 * fscrypt_base64url_decode() - base64url-decode a string 230 * @src: the string to decode. Doesn't need to be NUL-terminated. 231 * @srclen: the length of @src in bytes 232 * @dst: (output) the decoded binary data 233 * 234 * Decodes a string using base64url encoding, i.e. the "Base 64 Encoding with 235 * URL and Filename Safe Alphabet" specified by RFC 4648. '='-padding isn't 236 * accepted, nor are non-encoding characters such as whitespace. 237 * 238 * This implementation hasn't been optimized for performance. 239 * 240 * Return: the length of the resulting decoded binary data in bytes, 241 * or -1 if the string isn't a valid base64url string. 242 */ 243 static int fscrypt_base64url_decode(const char *src, int srclen, u8 *dst) 244 { 245 u32 ac = 0; 246 int bits = 0; 247 int i; 248 u8 *bp = dst; 249 250 for (i = 0; i < srclen; i++) { 251 const char *p = strchr(base64url_table, src[i]); 252 253 if (p == NULL || src[i] == 0) 254 return -1; 255 ac = (ac << 6) | (p - base64url_table); 256 bits += 6; 257 if (bits >= 8) { 258 bits -= 8; 259 *bp++ = (u8)(ac >> bits); 260 } 261 } 262 if (ac & ((1 << bits) - 1)) 263 return -1; 264 return bp - dst; 265 } 266 267 bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy, 268 u32 orig_len, u32 max_len, 269 u32 *encrypted_len_ret) 270 { 271 int padding = 4 << (fscrypt_policy_flags(policy) & 272 FSCRYPT_POLICY_FLAGS_PAD_MASK); 273 u32 encrypted_len; 274 275 if (orig_len > max_len) 276 return false; 277 encrypted_len = max_t(u32, orig_len, FSCRYPT_FNAME_MIN_MSG_LEN); 278 encrypted_len = round_up(encrypted_len, padding); 279 *encrypted_len_ret = min(encrypted_len, max_len); 280 return true; 281 } 282 283 /** 284 * fscrypt_fname_alloc_buffer() - allocate a buffer for presented filenames 285 * @max_encrypted_len: maximum length of encrypted filenames the buffer will be 286 * used to present 287 * @crypto_str: (output) buffer to allocate 288 * 289 * Allocate a buffer that is large enough to hold any decrypted or encoded 290 * filename (null-terminated), for the given maximum encrypted filename length. 291 * 292 * Return: 0 on success, -errno on failure 293 */ 294 int fscrypt_fname_alloc_buffer(u32 max_encrypted_len, 295 struct fscrypt_str *crypto_str) 296 { 297 u32 max_presented_len = max_t(u32, FSCRYPT_NOKEY_NAME_MAX_ENCODED, 298 max_encrypted_len); 299 300 crypto_str->name = kmalloc(max_presented_len + 1, GFP_NOFS); 301 if (!crypto_str->name) 302 return -ENOMEM; 303 crypto_str->len = max_presented_len; 304 return 0; 305 } 306 EXPORT_SYMBOL(fscrypt_fname_alloc_buffer); 307 308 /** 309 * fscrypt_fname_free_buffer() - free a buffer for presented filenames 310 * @crypto_str: the buffer to free 311 * 312 * Free a buffer that was allocated by fscrypt_fname_alloc_buffer(). 313 */ 314 void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str) 315 { 316 if (!crypto_str) 317 return; 318 kfree(crypto_str->name); 319 crypto_str->name = NULL; 320 } 321 EXPORT_SYMBOL(fscrypt_fname_free_buffer); 322 323 /** 324 * fscrypt_fname_disk_to_usr() - convert an encrypted filename to 325 * user-presentable form 326 * @inode: inode of the parent directory (for regular filenames) 327 * or of the symlink (for symlink targets) 328 * @hash: first part of the name's dirhash, if applicable. This only needs to 329 * be provided if the filename is located in an indexed directory whose 330 * encryption key may be unavailable. Not needed for symlink targets. 331 * @minor_hash: second part of the name's dirhash, if applicable 332 * @iname: encrypted filename to convert. May also be "." or "..", which 333 * aren't actually encrypted. 334 * @oname: output buffer for the user-presentable filename. The caller must 335 * have allocated enough space for this, e.g. using 336 * fscrypt_fname_alloc_buffer(). 337 * 338 * If the key is available, we'll decrypt the disk name. Otherwise, we'll 339 * encode it for presentation in fscrypt_nokey_name format. 340 * See struct fscrypt_nokey_name for details. 341 * 342 * Return: 0 on success, -errno on failure 343 */ 344 int fscrypt_fname_disk_to_usr(const struct inode *inode, 345 u32 hash, u32 minor_hash, 346 const struct fscrypt_str *iname, 347 struct fscrypt_str *oname) 348 { 349 const struct qstr qname = FSTR_TO_QSTR(iname); 350 struct fscrypt_nokey_name nokey_name; 351 u32 size; /* size of the unencoded no-key name */ 352 353 if (fscrypt_is_dot_dotdot(&qname)) { 354 oname->name[0] = '.'; 355 oname->name[iname->len - 1] = '.'; 356 oname->len = iname->len; 357 return 0; 358 } 359 360 if (iname->len < FSCRYPT_FNAME_MIN_MSG_LEN) 361 return -EUCLEAN; 362 363 if (fscrypt_has_encryption_key(inode)) 364 return fname_decrypt(inode, iname, oname); 365 366 /* 367 * Sanity check that struct fscrypt_nokey_name doesn't have padding 368 * between fields and that its encoded size never exceeds NAME_MAX. 369 */ 370 BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, dirhash) != 371 offsetof(struct fscrypt_nokey_name, bytes)); 372 BUILD_BUG_ON(offsetofend(struct fscrypt_nokey_name, bytes) != 373 offsetof(struct fscrypt_nokey_name, sha256)); 374 BUILD_BUG_ON(FSCRYPT_NOKEY_NAME_MAX_ENCODED > NAME_MAX); 375 376 nokey_name.dirhash[0] = hash; 377 nokey_name.dirhash[1] = minor_hash; 378 379 if (iname->len <= sizeof(nokey_name.bytes)) { 380 memcpy(nokey_name.bytes, iname->name, iname->len); 381 size = offsetof(struct fscrypt_nokey_name, bytes[iname->len]); 382 } else { 383 memcpy(nokey_name.bytes, iname->name, sizeof(nokey_name.bytes)); 384 /* Compute strong hash of remaining part of name. */ 385 sha256(&iname->name[sizeof(nokey_name.bytes)], 386 iname->len - sizeof(nokey_name.bytes), 387 nokey_name.sha256); 388 size = FSCRYPT_NOKEY_NAME_MAX; 389 } 390 oname->len = fscrypt_base64url_encode((const u8 *)&nokey_name, size, 391 oname->name); 392 return 0; 393 } 394 EXPORT_SYMBOL(fscrypt_fname_disk_to_usr); 395 396 /** 397 * fscrypt_setup_filename() - prepare to search a possibly encrypted directory 398 * @dir: the directory that will be searched 399 * @iname: the user-provided filename being searched for 400 * @lookup: 1 if we're allowed to proceed without the key because it's 401 * ->lookup() or we're finding the dir_entry for deletion; 0 if we cannot 402 * proceed without the key because we're going to create the dir_entry. 403 * @fname: the filename information to be filled in 404 * 405 * Given a user-provided filename @iname, this function sets @fname->disk_name 406 * to the name that would be stored in the on-disk directory entry, if possible. 407 * If the directory is unencrypted this is simply @iname. Else, if we have the 408 * directory's encryption key, then @iname is the plaintext, so we encrypt it to 409 * get the disk_name. 410 * 411 * Else, for keyless @lookup operations, @iname should be a no-key name, so we 412 * decode it to get the struct fscrypt_nokey_name. Non-@lookup operations will 413 * be impossible in this case, so we fail them with ENOKEY. 414 * 415 * If successful, fscrypt_free_filename() must be called later to clean up. 416 * 417 * Return: 0 on success, -errno on failure 418 */ 419 int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, 420 int lookup, struct fscrypt_name *fname) 421 { 422 struct fscrypt_nokey_name *nokey_name; 423 int ret; 424 425 memset(fname, 0, sizeof(struct fscrypt_name)); 426 fname->usr_fname = iname; 427 428 if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) { 429 fname->disk_name.name = (unsigned char *)iname->name; 430 fname->disk_name.len = iname->len; 431 return 0; 432 } 433 ret = fscrypt_get_encryption_info(dir, lookup); 434 if (ret) 435 return ret; 436 437 if (fscrypt_has_encryption_key(dir)) { 438 if (!fscrypt_fname_encrypted_size(&dir->i_crypt_info->ci_policy, 439 iname->len, NAME_MAX, 440 &fname->crypto_buf.len)) 441 return -ENAMETOOLONG; 442 fname->crypto_buf.name = kmalloc(fname->crypto_buf.len, 443 GFP_NOFS); 444 if (!fname->crypto_buf.name) 445 return -ENOMEM; 446 447 ret = fscrypt_fname_encrypt(dir, iname, fname->crypto_buf.name, 448 fname->crypto_buf.len); 449 if (ret) 450 goto errout; 451 fname->disk_name.name = fname->crypto_buf.name; 452 fname->disk_name.len = fname->crypto_buf.len; 453 return 0; 454 } 455 if (!lookup) 456 return -ENOKEY; 457 fname->is_nokey_name = true; 458 459 /* 460 * We don't have the key and we are doing a lookup; decode the 461 * user-supplied name 462 */ 463 464 if (iname->len > FSCRYPT_NOKEY_NAME_MAX_ENCODED) 465 return -ENOENT; 466 467 fname->crypto_buf.name = kmalloc(FSCRYPT_NOKEY_NAME_MAX, GFP_KERNEL); 468 if (fname->crypto_buf.name == NULL) 469 return -ENOMEM; 470 471 ret = fscrypt_base64url_decode(iname->name, iname->len, 472 fname->crypto_buf.name); 473 if (ret < (int)offsetof(struct fscrypt_nokey_name, bytes[1]) || 474 (ret > offsetof(struct fscrypt_nokey_name, sha256) && 475 ret != FSCRYPT_NOKEY_NAME_MAX)) { 476 ret = -ENOENT; 477 goto errout; 478 } 479 fname->crypto_buf.len = ret; 480 481 nokey_name = (void *)fname->crypto_buf.name; 482 fname->hash = nokey_name->dirhash[0]; 483 fname->minor_hash = nokey_name->dirhash[1]; 484 if (ret != FSCRYPT_NOKEY_NAME_MAX) { 485 /* The full ciphertext filename is available. */ 486 fname->disk_name.name = nokey_name->bytes; 487 fname->disk_name.len = 488 ret - offsetof(struct fscrypt_nokey_name, bytes); 489 } 490 return 0; 491 492 errout: 493 kfree(fname->crypto_buf.name); 494 return ret; 495 } 496 EXPORT_SYMBOL(fscrypt_setup_filename); 497 498 /** 499 * fscrypt_match_name() - test whether the given name matches a directory entry 500 * @fname: the name being searched for 501 * @de_name: the name from the directory entry 502 * @de_name_len: the length of @de_name in bytes 503 * 504 * Normally @fname->disk_name will be set, and in that case we simply compare 505 * that to the name stored in the directory entry. The only exception is that 506 * if we don't have the key for an encrypted directory and the name we're 507 * looking for is very long, then we won't have the full disk_name and instead 508 * we'll need to match against a fscrypt_nokey_name that includes a strong hash. 509 * 510 * Return: %true if the name matches, otherwise %false. 511 */ 512 bool fscrypt_match_name(const struct fscrypt_name *fname, 513 const u8 *de_name, u32 de_name_len) 514 { 515 const struct fscrypt_nokey_name *nokey_name = 516 (const void *)fname->crypto_buf.name; 517 u8 digest[SHA256_DIGEST_SIZE]; 518 519 if (likely(fname->disk_name.name)) { 520 if (de_name_len != fname->disk_name.len) 521 return false; 522 return !memcmp(de_name, fname->disk_name.name, de_name_len); 523 } 524 if (de_name_len <= sizeof(nokey_name->bytes)) 525 return false; 526 if (memcmp(de_name, nokey_name->bytes, sizeof(nokey_name->bytes))) 527 return false; 528 sha256(&de_name[sizeof(nokey_name->bytes)], 529 de_name_len - sizeof(nokey_name->bytes), digest); 530 return !memcmp(digest, nokey_name->sha256, sizeof(digest)); 531 } 532 EXPORT_SYMBOL_GPL(fscrypt_match_name); 533 534 /** 535 * fscrypt_fname_siphash() - calculate the SipHash of a filename 536 * @dir: the parent directory 537 * @name: the filename to calculate the SipHash of 538 * 539 * Given a plaintext filename @name and a directory @dir which uses SipHash as 540 * its dirhash method and has had its fscrypt key set up, this function 541 * calculates the SipHash of that name using the directory's secret dirhash key. 542 * 543 * Return: the SipHash of @name using the hash key of @dir 544 */ 545 u64 fscrypt_fname_siphash(const struct inode *dir, const struct qstr *name) 546 { 547 const struct fscrypt_info *ci = dir->i_crypt_info; 548 549 WARN_ON(!ci->ci_dirhash_key_initialized); 550 551 return siphash(name->name, name->len, &ci->ci_dirhash_key); 552 } 553 EXPORT_SYMBOL_GPL(fscrypt_fname_siphash); 554 555 /* 556 * Validate dentries in encrypted directories to make sure we aren't potentially 557 * caching stale dentries after a key has been added. 558 */ 559 int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags) 560 { 561 struct dentry *dir; 562 int err; 563 int valid; 564 565 /* 566 * Plaintext names are always valid, since fscrypt doesn't support 567 * reverting to no-key names without evicting the directory's inode 568 * -- which implies eviction of the dentries in the directory. 569 */ 570 if (!(dentry->d_flags & DCACHE_NOKEY_NAME)) 571 return 1; 572 573 /* 574 * No-key name; valid if the directory's key is still unavailable. 575 * 576 * Although fscrypt forbids rename() on no-key names, we still must use 577 * dget_parent() here rather than use ->d_parent directly. That's 578 * because a corrupted fs image may contain directory hard links, which 579 * the VFS handles by moving the directory's dentry tree in the dcache 580 * each time ->lookup() finds the directory and it already has a dentry 581 * elsewhere. Thus ->d_parent can be changing, and we must safely grab 582 * a reference to some ->d_parent to prevent it from being freed. 583 */ 584 585 if (flags & LOOKUP_RCU) 586 return -ECHILD; 587 588 dir = dget_parent(dentry); 589 /* 590 * Pass allow_unsupported=true, so that files with an unsupported 591 * encryption policy can be deleted. 592 */ 593 err = fscrypt_get_encryption_info(d_inode(dir), true); 594 valid = !fscrypt_has_encryption_key(d_inode(dir)); 595 dput(dir); 596 597 if (err < 0) 598 return err; 599 600 return valid; 601 } 602 EXPORT_SYMBOL_GPL(fscrypt_d_revalidate); 603