include/linux/fscrypt.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * fscrypt.h: declarations for per-file encryption
   4  *
   5  * Filesystems that implement per-file encryption must include this header
   6  * file.
   7  *
   8  * Copyright (C) 2015, Google, Inc.
   9  *
  10  * Written by Michael Halcrow, 2015.
  11  * Modified by Jaegeuk Kim, 2015.
  12  */
  13 #ifndef _LINUX_FSCRYPT_H
  14 #define _LINUX_FSCRYPT_H
  15
  16 #include <linux/fs.h>
  17 #include <linux/mm.h>
  18 #include <linux/parser.h>
  19 #include <linux/slab.h>
  20 #include <uapi/linux/fscrypt.h>
  21
  22 #define FS_CRYPTO_BLOCK_SIZE            16
  23
  24 union fscrypt_context;
  25 struct fscrypt_info;
  26 struct seq_file;
  27
  28 struct fscrypt_str {
  29         unsigned char *name;
  30         u32 len;
  31 };
  32
  33 struct fscrypt_name {
  34         const struct qstr *usr_fname;
  35         struct fscrypt_str disk_name;
  36         u32 hash;
  37         u32 minor_hash;
  38         struct fscrypt_str crypto_buf;
  39         bool is_ciphertext_name;
  40 };
  41
  42 #define FSTR_INIT(n, l)         { .name = n, .len = l }
  43 #define FSTR_TO_QSTR(f)         QSTR_INIT((f)->name, (f)->len)
  44 #define fname_name(p)           ((p)->disk_name.name)
  45 #define fname_len(p)            ((p)->disk_name.len)
  46
  47 /* Maximum value for the third parameter of fscrypt_operations.set_context(). */
  48 #define FSCRYPT_SET_CONTEXT_MAX_SIZE    40
  49
  50 #ifdef CONFIG_FS_ENCRYPTION
  51 /*
  52  * fscrypt superblock flags
  53  */
  54 #define FS_CFLG_OWN_PAGES (1U << 1)
  55
  56 /*
  57  * crypto operations for filesystems
  58  */
  59 struct fscrypt_operations {
  60         unsigned int flags;
  61         const char *key_prefix;
  62         int (*get_context)(struct inode *inode, void *ctx, size_t len);
  63         int (*set_context)(struct inode *inode, const void *ctx, size_t len,
  64                            void *fs_data);
  65         const union fscrypt_context *(*get_dummy_context)(
  66                 struct super_block *sb);
  67         bool (*empty_dir)(struct inode *inode);
  68         unsigned int max_namelen;
  69         bool (*has_stable_inodes)(struct super_block *sb);
  70         void (*get_ino_and_lblk_bits)(struct super_block *sb,
  71                                       int *ino_bits_ret, int *lblk_bits_ret);
  72 };
  73
  74 static inline bool fscrypt_has_encryption_key(const struct inode *inode)
  75 {
  76         /* pairs with cmpxchg_release() in fscrypt_get_encryption_info() */
  77         return READ_ONCE(inode->i_crypt_info) != NULL;
  78 }
  79
  80 /**
  81  * fscrypt_needs_contents_encryption() - check whether an inode needs
  82  *                                       contents encryption
  83  * @inode: the inode to check
  84  *
  85  * Return: %true iff the inode is an encrypted regular file and the kernel was
  86  * built with fscrypt support.
  87  *
  88  * If you need to know whether the encrypt bit is set even when the kernel was
  89  * built without fscrypt support, you must use IS_ENCRYPTED() directly instead.
  90  */
  91 static inline bool fscrypt_needs_contents_encryption(const struct inode *inode)
  92 {
  93         return IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode);
  94 }
  95
  96 static inline const union fscrypt_context *
  97 fscrypt_get_dummy_context(struct super_block *sb)
  98 {
  99         if (!sb->s_cop->get_dummy_context)
 100                 return NULL;
 101         return sb->s_cop->get_dummy_context(sb);
 102 }
 103
 104 /*
 105  * When d_splice_alias() moves a directory's encrypted alias to its decrypted
 106  * alias as a result of the encryption key being added, DCACHE_ENCRYPTED_NAME
 107  * must be cleared.  Note that we don't have to support arbitrary moves of this
 108  * flag because fscrypt doesn't allow encrypted aliases to be the source or
 109  * target of a rename().
 110  */
 111 static inline void fscrypt_handle_d_move(struct dentry *dentry)
 112 {
 113         dentry->d_flags &= ~DCACHE_ENCRYPTED_NAME;
 114 }
 115
 116 /* crypto.c */
 117 void fscrypt_enqueue_decrypt_work(struct work_struct *);
 118
 119 struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
 120                                               unsigned int len,
 121                                               unsigned int offs,
 122                                               gfp_t gfp_flags);
 123 int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
 124                                   unsigned int len, unsigned int offs,
 125                                   u64 lblk_num, gfp_t gfp_flags);
 126
 127 int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
 128                                      unsigned int offs);
 129 int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
 130                                   unsigned int len, unsigned int offs,
 131                                   u64 lblk_num);
 132
 133 static inline bool fscrypt_is_bounce_page(struct page *page)
 134 {
 135         return page->mapping == NULL;
 136 }
 137
 138 static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
 139 {
 140         return (struct page *)page_private(bounce_page);
 141 }
 142
 143 void fscrypt_free_bounce_page(struct page *bounce_page);
 144
 145 /* policy.c */
 146 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg);
 147 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg);
 148 int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *arg);
 149 int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg);
 150 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child);
 151 int fscrypt_inherit_context(struct inode *parent, struct inode *child,
 152                             void *fs_data, bool preload);
 153
 154 struct fscrypt_dummy_context {
 155         const union fscrypt_context *ctx;
 156 };
 157
 158 int fscrypt_set_test_dummy_encryption(struct super_block *sb,
 159                                       const substring_t *arg,
 160                                       struct fscrypt_dummy_context *dummy_ctx);
 161 void fscrypt_show_test_dummy_encryption(struct seq_file *seq, char sep,
 162                                         struct super_block *sb);
 163 static inline void
 164 fscrypt_free_dummy_context(struct fscrypt_dummy_context *dummy_ctx)
 165 {
 166         kfree(dummy_ctx->ctx);
 167         dummy_ctx->ctx = NULL;
 168 }
 169
 170 /* keyring.c */
 171 void fscrypt_sb_free(struct super_block *sb);
 172 int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
 173 int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg);
 174 int fscrypt_ioctl_remove_key_all_users(struct file *filp, void __user *arg);
 175 int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg);
 176
 177 /* keysetup.c */
 178 int fscrypt_get_encryption_info(struct inode *inode);
 179 void fscrypt_put_encryption_info(struct inode *inode);
 180 void fscrypt_free_inode(struct inode *inode);
 181 int fscrypt_drop_inode(struct inode *inode);
 182
 183 /* fname.c */
 184 int fscrypt_setup_filename(struct inode *inode, const struct qstr *iname,
 185                            int lookup, struct fscrypt_name *fname);
 186
 187 static inline void fscrypt_free_filename(struct fscrypt_name *fname)
 188 {
 189         kfree(fname->crypto_buf.name);
 190 }
 191
 192 int fscrypt_fname_alloc_buffer(const struct inode *inode, u32 max_encrypted_len,
 193                                struct fscrypt_str *crypto_str);
 194 void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str);
 195 int fscrypt_fname_disk_to_usr(const struct inode *inode,
 196                               u32 hash, u32 minor_hash,
 197                               const struct fscrypt_str *iname,
 198                               struct fscrypt_str *oname);
 199 bool fscrypt_match_name(const struct fscrypt_name *fname,
 200                         const u8 *de_name, u32 de_name_len);
 201 u64 fscrypt_fname_siphash(const struct inode *dir, const struct qstr *name);
 202
 203 /* bio.c */
 204 void fscrypt_decrypt_bio(struct bio *bio);
 205 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 206                           sector_t pblk, unsigned int len);
 207
 208 /* hooks.c */
 209 int fscrypt_file_open(struct inode *inode, struct file *filp);
 210 int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
 211                            struct dentry *dentry);
 212 int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
 213                              struct inode *new_dir, struct dentry *new_dentry,
 214                              unsigned int flags);
 215 int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
 216                              struct fscrypt_name *fname);
 217 int fscrypt_prepare_setflags(struct inode *inode,
 218                              unsigned int oldflags, unsigned int flags);
 219 int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
 220                               unsigned int max_len,
 221                               struct fscrypt_str *disk_link);
 222 int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
 223                               unsigned int len, struct fscrypt_str *disk_link);
 224 const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
 225                                 unsigned int max_size,
 226                                 struct delayed_call *done);
 227 static inline void fscrypt_set_ops(struct super_block *sb,
 228                                    const struct fscrypt_operations *s_cop)
 229 {
 230         sb->s_cop = s_cop;
 231 }
 232 #else  /* !CONFIG_FS_ENCRYPTION */
 233
 234 static inline bool fscrypt_has_encryption_key(const struct inode *inode)
 235 {
 236         return false;
 237 }
 238
 239 static inline bool fscrypt_needs_contents_encryption(const struct inode *inode)
 240 {
 241         return false;
 242 }
 243
 244 static inline const union fscrypt_context *
 245 fscrypt_get_dummy_context(struct super_block *sb)
 246 {
 247         return NULL;
 248 }
 249
 250 static inline void fscrypt_handle_d_move(struct dentry *dentry)
 251 {
 252 }
 253
 254 /* crypto.c */
 255 static inline void fscrypt_enqueue_decrypt_work(struct work_struct *work)
 256 {
 257 }
 258
 259 static inline struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
 260                                                             unsigned int len,
 261                                                             unsigned int offs,
 262                                                             gfp_t gfp_flags)
 263 {
 264         return ERR_PTR(-EOPNOTSUPP);
 265 }
 266
 267 static inline int fscrypt_encrypt_block_inplace(const struct inode *inode,
 268                                                 struct page *page,
 269                                                 unsigned int len,
 270                                                 unsigned int offs, u64 lblk_num,
 271                                                 gfp_t gfp_flags)
 272 {
 273         return -EOPNOTSUPP;
 274 }
 275
 276 static inline int fscrypt_decrypt_pagecache_blocks(struct page *page,
 277                                                    unsigned int len,
 278                                                    unsigned int offs)
 279 {
 280         return -EOPNOTSUPP;
 281 }
 282
 283 static inline int fscrypt_decrypt_block_inplace(const struct inode *inode,
 284                                                 struct page *page,
 285                                                 unsigned int len,
 286                                                 unsigned int offs, u64 lblk_num)
 287 {
 288         return -EOPNOTSUPP;
 289 }
 290
 291 static inline bool fscrypt_is_bounce_page(struct page *page)
 292 {
 293         return false;
 294 }
 295
 296 static inline struct page *fscrypt_pagecache_page(struct page *bounce_page)
 297 {
 298         WARN_ON_ONCE(1);
 299         return ERR_PTR(-EINVAL);
 300 }
 301
 302 static inline void fscrypt_free_bounce_page(struct page *bounce_page)
 303 {
 304 }
 305
 306 /* policy.c */
 307 static inline int fscrypt_ioctl_set_policy(struct file *filp,
 308                                            const void __user *arg)
 309 {
 310         return -EOPNOTSUPP;
 311 }
 312
 313 static inline int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 314 {
 315         return -EOPNOTSUPP;
 316 }
 317
 318 static inline int fscrypt_ioctl_get_policy_ex(struct file *filp,
 319                                               void __user *arg)
 320 {
 321         return -EOPNOTSUPP;
 322 }
 323
 324 static inline int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg)
 325 {
 326         return -EOPNOTSUPP;
 327 }
 328
 329 static inline int fscrypt_has_permitted_context(struct inode *parent,
 330                                                 struct inode *child)
 331 {
 332         return 0;
 333 }
 334
 335 static inline int fscrypt_inherit_context(struct inode *parent,
 336                                           struct inode *child,
 337                                           void *fs_data, bool preload)
 338 {
 339         return -EOPNOTSUPP;
 340 }
 341
 342 struct fscrypt_dummy_context {
 343 };
 344
 345 static inline void fscrypt_show_test_dummy_encryption(struct seq_file *seq,
 346                                                       char sep,
 347                                                       struct super_block *sb)
 348 {
 349 }
 350
 351 static inline void
 352 fscrypt_free_dummy_context(struct fscrypt_dummy_context *dummy_ctx)
 353 {
 354 }
 355
 356 /* keyring.c */
 357 static inline void fscrypt_sb_free(struct super_block *sb)
 358 {
 359 }
 360
 361 static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg)
 362 {
 363         return -EOPNOTSUPP;
 364 }
 365
 366 static inline int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg)
 367 {
 368         return -EOPNOTSUPP;
 369 }
 370
 371 static inline int fscrypt_ioctl_remove_key_all_users(struct file *filp,
 372                                                      void __user *arg)
 373 {
 374         return -EOPNOTSUPP;
 375 }
 376
 377 static inline int fscrypt_ioctl_get_key_status(struct file *filp,
 378                                                void __user *arg)
 379 {
 380         return -EOPNOTSUPP;
 381 }
 382
 383 /* keysetup.c */
 384 static inline int fscrypt_get_encryption_info(struct inode *inode)
 385 {
 386         return -EOPNOTSUPP;
 387 }
 388
 389 static inline void fscrypt_put_encryption_info(struct inode *inode)
 390 {
 391         return;
 392 }
 393
 394 static inline void fscrypt_free_inode(struct inode *inode)
 395 {
 396 }
 397
 398 static inline int fscrypt_drop_inode(struct inode *inode)
 399 {
 400         return 0;
 401 }
 402
 403  /* fname.c */
 404 static inline int fscrypt_setup_filename(struct inode *dir,
 405                                          const struct qstr *iname,
 406                                          int lookup, struct fscrypt_name *fname)
 407 {
 408         if (IS_ENCRYPTED(dir))
 409                 return -EOPNOTSUPP;
 410
 411         memset(fname, 0, sizeof(*fname));
 412         fname->usr_fname = iname;
 413         fname->disk_name.name = (unsigned char *)iname->name;
 414         fname->disk_name.len = iname->len;
 415         return 0;
 416 }
 417
 418 static inline void fscrypt_free_filename(struct fscrypt_name *fname)
 419 {
 420         return;
 421 }
 422
 423 static inline int fscrypt_fname_alloc_buffer(const struct inode *inode,
 424                                              u32 max_encrypted_len,
 425                                              struct fscrypt_str *crypto_str)
 426 {
 427         return -EOPNOTSUPP;
 428 }
 429
 430 static inline void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str)
 431 {
 432         return;
 433 }
 434
 435 static inline int fscrypt_fname_disk_to_usr(const struct inode *inode,
 436                                             u32 hash, u32 minor_hash,
 437                                             const struct fscrypt_str *iname,
 438                                             struct fscrypt_str *oname)
 439 {
 440         return -EOPNOTSUPP;
 441 }
 442
 443 static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
 444                                       const u8 *de_name, u32 de_name_len)
 445 {
 446         /* Encryption support disabled; use standard comparison */
 447         if (de_name_len != fname->disk_name.len)
 448                 return false;
 449         return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
 450 }
 451
 452 static inline u64 fscrypt_fname_siphash(const struct inode *dir,
 453                                         const struct qstr *name)
 454 {
 455         WARN_ON_ONCE(1);
 456         return 0;
 457 }
 458
 459 /* bio.c */
 460 static inline void fscrypt_decrypt_bio(struct bio *bio)
 461 {
 462 }
 463
 464 static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 465                                         sector_t pblk, unsigned int len)
 466 {
 467         return -EOPNOTSUPP;
 468 }
 469
 470 /* hooks.c */
 471
 472 static inline int fscrypt_file_open(struct inode *inode, struct file *filp)
 473 {
 474         if (IS_ENCRYPTED(inode))
 475                 return -EOPNOTSUPP;
 476         return 0;
 477 }
 478
 479 static inline int __fscrypt_prepare_link(struct inode *inode, struct inode *dir,
 480                                          struct dentry *dentry)
 481 {
 482         return -EOPNOTSUPP;
 483 }
 484
 485 static inline int __fscrypt_prepare_rename(struct inode *old_dir,
 486                                            struct dentry *old_dentry,
 487                                            struct inode *new_dir,
 488                                            struct dentry *new_dentry,
 489                                            unsigned int flags)
 490 {
 491         return -EOPNOTSUPP;
 492 }
 493
 494 static inline int __fscrypt_prepare_lookup(struct inode *dir,
 495                                            struct dentry *dentry,
 496                                            struct fscrypt_name *fname)
 497 {
 498         return -EOPNOTSUPP;
 499 }
 500
 501 static inline int fscrypt_prepare_setflags(struct inode *inode,
 502                                            unsigned int oldflags,
 503                                            unsigned int flags)
 504 {
 505         return 0;
 506 }
 507
 508 static inline int __fscrypt_prepare_symlink(struct inode *dir,
 509                                             unsigned int len,
 510                                             unsigned int max_len,
 511                                             struct fscrypt_str *disk_link)
 512 {
 513         return -EOPNOTSUPP;
 514 }
 515
 516
 517 static inline int __fscrypt_encrypt_symlink(struct inode *inode,
 518                                             const char *target,
 519                                             unsigned int len,
 520                                             struct fscrypt_str *disk_link)
 521 {
 522         return -EOPNOTSUPP;
 523 }
 524
 525 static inline const char *fscrypt_get_symlink(struct inode *inode,
 526                                               const void *caddr,
 527                                               unsigned int max_size,
 528                                               struct delayed_call *done)
 529 {
 530         return ERR_PTR(-EOPNOTSUPP);
 531 }
 532
 533 static inline void fscrypt_set_ops(struct super_block *sb,
 534                                    const struct fscrypt_operations *s_cop)
 535 {
 536 }
 537
 538 #endif  /* !CONFIG_FS_ENCRYPTION */
 539
 540 /**
 541  * fscrypt_require_key() - require an inode's encryption key
 542  * @inode: the inode we need the key for
 543  *
 544  * If the inode is encrypted, set up its encryption key if not already done.
 545  * Then require that the key be present and return -ENOKEY otherwise.
 546  *
 547  * No locks are needed, and the key will live as long as the struct inode --- so
 548  * it won't go away from under you.
 549  *
 550  * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
 551  * if a problem occurred while setting up the encryption key.
 552  */
 553 static inline int fscrypt_require_key(struct inode *inode)
 554 {
 555         if (IS_ENCRYPTED(inode)) {
 556                 int err = fscrypt_get_encryption_info(inode);
 557
 558                 if (err)
 559                         return err;
 560                 if (!fscrypt_has_encryption_key(inode))
 561                         return -ENOKEY;
 562         }
 563         return 0;
 564 }
 565
 566 /**
 567  * fscrypt_prepare_link() - prepare to link an inode into a possibly-encrypted
 568  *                          directory
 569  * @old_dentry: an existing dentry for the inode being linked
 570  * @dir: the target directory
 571  * @dentry: negative dentry for the target filename
 572  *
 573  * A new link can only be added to an encrypted directory if the directory's
 574  * encryption key is available --- since otherwise we'd have no way to encrypt
 575  * the filename.  Therefore, we first set up the directory's encryption key (if
 576  * not already done) and return an error if it's unavailable.
 577  *
 578  * We also verify that the link will not violate the constraint that all files
 579  * in an encrypted directory tree use the same encryption policy.
 580  *
 581  * Return: 0 on success, -ENOKEY if the directory's encryption key is missing,
 582  * -EXDEV if the link would result in an inconsistent encryption policy, or
 583  * another -errno code.
 584  */
 585 static inline int fscrypt_prepare_link(struct dentry *old_dentry,
 586                                        struct inode *dir,
 587                                        struct dentry *dentry)
 588 {
 589         if (IS_ENCRYPTED(dir))
 590                 return __fscrypt_prepare_link(d_inode(old_dentry), dir, dentry);
 591         return 0;
 592 }
 593
 594 /**
 595  * fscrypt_prepare_rename() - prepare for a rename between possibly-encrypted
 596  *                            directories
 597  * @old_dir: source directory
 598  * @old_dentry: dentry for source file
 599  * @new_dir: target directory
 600  * @new_dentry: dentry for target location (may be negative unless exchanging)
 601  * @flags: rename flags (we care at least about %RENAME_EXCHANGE)
 602  *
 603  * Prepare for ->rename() where the source and/or target directories may be
 604  * encrypted.  A new link can only be added to an encrypted directory if the
 605  * directory's encryption key is available --- since otherwise we'd have no way
 606  * to encrypt the filename.  A rename to an existing name, on the other hand,
 607  * *is* cryptographically possible without the key.  However, we take the more
 608  * conservative approach and just forbid all no-key renames.
 609  *
 610  * We also verify that the rename will not violate the constraint that all files
 611  * in an encrypted directory tree use the same encryption policy.
 612  *
 613  * Return: 0 on success, -ENOKEY if an encryption key is missing, -EXDEV if the
 614  * rename would cause inconsistent encryption policies, or another -errno code.
 615  */
 616 static inline int fscrypt_prepare_rename(struct inode *old_dir,
 617                                          struct dentry *old_dentry,
 618                                          struct inode *new_dir,
 619                                          struct dentry *new_dentry,
 620                                          unsigned int flags)
 621 {
 622         if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir))
 623                 return __fscrypt_prepare_rename(old_dir, old_dentry,
 624                                                 new_dir, new_dentry, flags);
 625         return 0;
 626 }
 627
 628 /**
 629  * fscrypt_prepare_lookup() - prepare to lookup a name in a possibly-encrypted
 630  *                            directory
 631  * @dir: directory being searched
 632  * @dentry: filename being looked up
 633  * @fname: (output) the name to use to search the on-disk directory
 634  *
 635  * Prepare for ->lookup() in a directory which may be encrypted by determining
 636  * the name that will actually be used to search the directory on-disk.  Lookups
 637  * can be done with or without the directory's encryption key; without the key,
 638  * filenames are presented in encrypted form.  Therefore, we'll try to set up
 639  * the directory's encryption key, but even without it the lookup can continue.
 640  *
 641  * This also installs a custom ->d_revalidate() method which will invalidate the
 642  * dentry if it was created without the key and the key is later added.
 643  *
 644  * Return: 0 on success; -ENOENT if key is unavailable but the filename isn't a
 645  * correctly formed encoded ciphertext name, so a negative dentry should be
 646  * created; or another -errno code.
 647  */
 648 static inline int fscrypt_prepare_lookup(struct inode *dir,
 649                                          struct dentry *dentry,
 650                                          struct fscrypt_name *fname)
 651 {
 652         if (IS_ENCRYPTED(dir))
 653                 return __fscrypt_prepare_lookup(dir, dentry, fname);
 654
 655         memset(fname, 0, sizeof(*fname));
 656         fname->usr_fname = &dentry->d_name;
 657         fname->disk_name.name = (unsigned char *)dentry->d_name.name;
 658         fname->disk_name.len = dentry->d_name.len;
 659         return 0;
 660 }
 661
 662 /**
 663  * fscrypt_prepare_setattr() - prepare to change a possibly-encrypted inode's
 664  *                             attributes
 665  * @dentry: dentry through which the inode is being changed
 666  * @attr: attributes to change
 667  *
 668  * Prepare for ->setattr() on a possibly-encrypted inode.  On an encrypted file,
 669  * most attribute changes are allowed even without the encryption key.  However,
 670  * without the encryption key we do have to forbid truncates.  This is needed
 671  * because the size being truncated to may not be a multiple of the filesystem
 672  * block size, and in that case we'd have to decrypt the final block, zero the
 673  * portion past i_size, and re-encrypt it.  (We *could* allow truncating to a
 674  * filesystem block boundary, but it's simpler to just forbid all truncates ---
 675  * and we already forbid all other contents modifications without the key.)
 676  *
 677  * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
 678  * if a problem occurred while setting up the encryption key.
 679  */
 680 static inline int fscrypt_prepare_setattr(struct dentry *dentry,
 681                                           struct iattr *attr)
 682 {
 683         if (attr->ia_valid & ATTR_SIZE)
 684                 return fscrypt_require_key(d_inode(dentry));
 685         return 0;
 686 }
 687
 688 /**
 689  * fscrypt_prepare_symlink() - prepare to create a possibly-encrypted symlink
 690  * @dir: directory in which the symlink is being created
 691  * @target: plaintext symlink target
 692  * @len: length of @target excluding null terminator
 693  * @max_len: space the filesystem has available to store the symlink target
 694  * @disk_link: (out) the on-disk symlink target being prepared
 695  *
 696  * This function computes the size the symlink target will require on-disk,
 697  * stores it in @disk_link->len, and validates it against @max_len.  An
 698  * encrypted symlink may be longer than the original.
 699  *
 700  * Additionally, @disk_link->name is set to @target if the symlink will be
 701  * unencrypted, but left NULL if the symlink will be encrypted.  For encrypted
 702  * symlinks, the filesystem must call fscrypt_encrypt_symlink() to create the
 703  * on-disk target later.  (The reason for the two-step process is that some
 704  * filesystems need to know the size of the symlink target before creating the
 705  * inode, e.g. to determine whether it will be a "fast" or "slow" symlink.)
 706  *
 707  * Return: 0 on success, -ENAMETOOLONG if the symlink target is too long,
 708  * -ENOKEY if the encryption key is missing, or another -errno code if a problem
 709  * occurred while setting up the encryption key.
 710  */
 711 static inline int fscrypt_prepare_symlink(struct inode *dir,
 712                                           const char *target,
 713                                           unsigned int len,
 714                                           unsigned int max_len,
 715                                           struct fscrypt_str *disk_link)
 716 {
 717         if (IS_ENCRYPTED(dir) || fscrypt_get_dummy_context(dir->i_sb) != NULL)
 718                 return __fscrypt_prepare_symlink(dir, len, max_len, disk_link);
 719
 720         disk_link->name = (unsigned char *)target;
 721         disk_link->len = len + 1;
 722         if (disk_link->len > max_len)
 723                 return -ENAMETOOLONG;
 724         return 0;
 725 }
 726
 727 /**
 728  * fscrypt_encrypt_symlink() - encrypt the symlink target if needed
 729  * @inode: symlink inode
 730  * @target: plaintext symlink target
 731  * @len: length of @target excluding null terminator
 732  * @disk_link: (in/out) the on-disk symlink target being prepared
 733  *
 734  * If the symlink target needs to be encrypted, then this function encrypts it
 735  * into @disk_link->name.  fscrypt_prepare_symlink() must have been called
 736  * previously to compute @disk_link->len.  If the filesystem did not allocate a
 737  * buffer for @disk_link->name after calling fscrypt_prepare_link(), then one
 738  * will be kmalloc()'ed and the filesystem will be responsible for freeing it.
 739  *
 740  * Return: 0 on success, -errno on failure
 741  */
 742 static inline int fscrypt_encrypt_symlink(struct inode *inode,
 743                                           const char *target,
 744                                           unsigned int len,
 745                                           struct fscrypt_str *disk_link)
 746 {
 747         if (IS_ENCRYPTED(inode))
 748                 return __fscrypt_encrypt_symlink(inode, target, len, disk_link);
 749         return 0;
 750 }
 751
 752 /* If *pagep is a bounce page, free it and set *pagep to the pagecache page */
 753 static inline void fscrypt_finalize_bounce_page(struct page **pagep)
 754 {
 755         struct page *page = *pagep;
 756
 757         if (fscrypt_is_bounce_page(page)) {
 758                 *pagep = fscrypt_pagecache_page(page);
 759                 fscrypt_free_bounce_page(page);
 760         }
 761 }
 762
 763 #endif  /* _LINUX_FSCRYPT_H */