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