fs/ecryptfs/mmap.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * eCryptfs: Linux filesystem encryption layer
   4  * This is where eCryptfs coordinates the symmetric encryption and
   5  * decryption of the file data as it passes between the lower
   6  * encrypted file and the upper decrypted file.
   7  *
   8  * Copyright (C) 1997-2003 Erez Zadok
   9  * Copyright (C) 2001-2003 Stony Brook University
  10  * Copyright (C) 2004-2007 International Business Machines Corp.
  11  *   Author(s): Michael A. Halcrow <[email protected]>
  12  */
  13
  14 #include <linux/pagemap.h>
  15 #include <linux/writeback.h>
  16 #include <linux/page-flags.h>
  17 #include <linux/mount.h>
  18 #include <linux/file.h>
  19 #include <linux/scatterlist.h>
  20 #include <linux/slab.h>
  21 #include <linux/xattr.h>
  22 #include <asm/unaligned.h>
  23 #include "ecryptfs_kernel.h"
  24
  25 /*
  26  * ecryptfs_get_locked_page
  27  *
  28  * Get one page from cache or lower f/s, return error otherwise.
  29  *
  30  * Returns locked and up-to-date page (if ok), with increased
  31  * refcnt.
  32  */
  33 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
  34 {
  35         struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
  36         if (!IS_ERR(page))
  37                 lock_page(page);
  38         return page;
  39 }
  40
  41 /**
  42  * ecryptfs_writepage
  43  * @page: Page that is locked before this call is made
  44  * @wbc: Write-back control structure
  45  *
  46  * Returns zero on success; non-zero otherwise
  47  *
  48  * This is where we encrypt the data and pass the encrypted data to
  49  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
  50  * entire underlying packets.
  51  */
  52 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  53 {
  54         int rc;
  55
  56         rc = ecryptfs_encrypt_page(page);
  57         if (rc) {
  58                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  59                                 "page (upper index [0x%.16lx])\n", page->index);
  60                 ClearPageUptodate(page);
  61                 goto out;
  62         }
  63         SetPageUptodate(page);
  64 out:
  65         unlock_page(page);
  66         return rc;
  67 }
  68
  69 static void strip_xattr_flag(char *page_virt,
  70                              struct ecryptfs_crypt_stat *crypt_stat)
  71 {
  72         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  73                 size_t written;
  74
  75                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  76                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  77                                                 &written);
  78                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  79         }
  80 }
  81
  82 /*
  83  *   Header Extent:
  84  *     Octets 0-7:        Unencrypted file size (big-endian)
  85  *     Octets 8-15:       eCryptfs special marker
  86  *     Octets 16-19:      Flags
  87  *      Octet 16:         File format version number (between 0 and 255)
  88  *      Octets 17-18:     Reserved
  89  *      Octet 19:         Bit 1 (lsb): Reserved
  90  *                        Bit 2: Encrypted?
  91  *                        Bits 3-8: Reserved
  92  *     Octets 20-23:      Header extent size (big-endian)
  93  *     Octets 24-25:      Number of header extents at front of file
  94  *                        (big-endian)
  95  *     Octet  26:         Begin RFC 2440 authentication token packet set
  96  */
  97
  98 /**
  99  * ecryptfs_copy_up_encrypted_with_header
 100  * @page: Sort of a ``virtual'' representation of the encrypted lower
 101  *        file. The actual lower file does not have the metadata in
 102  *        the header. This is locked.
 103  * @crypt_stat: The eCryptfs inode's cryptographic context
 104  *
 105  * The ``view'' is the version of the file that userspace winds up
 106  * seeing, with the header information inserted.
 107  */
 108 static int
 109 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 110                                        struct ecryptfs_crypt_stat *crypt_stat)
 111 {
 112         loff_t extent_num_in_page = 0;
 113         loff_t num_extents_per_page = (PAGE_SIZE
 114                                        / crypt_stat->extent_size);
 115         int rc = 0;
 116
 117         while (extent_num_in_page < num_extents_per_page) {
 118                 loff_t view_extent_num = ((((loff_t)page->index)
 119                                            * num_extents_per_page)
 120                                           + extent_num_in_page);
 121                 size_t num_header_extents_at_front =
 122                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 123
 124                 if (view_extent_num < num_header_extents_at_front) {
 125                         /* This is a header extent */
 126                         char *page_virt;
 127
 128                         page_virt = kmap_atomic(page);
 129                         memset(page_virt, 0, PAGE_SIZE);
 130                         /* TODO: Support more than one header extent */
 131                         if (view_extent_num == 0) {
 132                                 size_t written;
 133
 134                                 rc = ecryptfs_read_xattr_region(
 135                                         page_virt, page->mapping->host);
 136                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 137                                 ecryptfs_write_header_metadata(page_virt + 20,
 138                                                                crypt_stat,
 139                                                                &written);
 140                         }
 141                         kunmap_atomic(page_virt);
 142                         flush_dcache_page(page);
 143                         if (rc) {
 144                                 printk(KERN_ERR "%s: Error reading xattr "
 145                                        "region; rc = [%d]\n", __func__, rc);
 146                                 goto out;
 147                         }
 148                 } else {
 149                         /* This is an encrypted data extent */
 150                         loff_t lower_offset =
 151                                 ((view_extent_num * crypt_stat->extent_size)
 152                                  - crypt_stat->metadata_size);
 153
 154                         rc = ecryptfs_read_lower_page_segment(
 155                                 page, (lower_offset >> PAGE_SHIFT),
 156                                 (lower_offset & ~PAGE_MASK),
 157                                 crypt_stat->extent_size, page->mapping->host);
 158                         if (rc) {
 159                                 printk(KERN_ERR "%s: Error attempting to read "
 160                                        "extent at offset [%lld] in the lower "
 161                                        "file; rc = [%d]\n", __func__,
 162                                        lower_offset, rc);
 163                                 goto out;
 164                         }
 165                 }
 166                 extent_num_in_page++;
 167         }
 168 out:
 169         return rc;
 170 }
 171
 172 /**
 173  * ecryptfs_read_folio
 174  * @file: An eCryptfs file
 175  * @folio: Folio from eCryptfs inode mapping into which to stick the read data
 176  *
 177  * Read in a folio, decrypting if necessary.
 178  *
 179  * Returns zero on success; non-zero on error.
 180  */
 181 static int ecryptfs_read_folio(struct file *file, struct folio *folio)
 182 {
 183         struct page *page = &folio->page;
 184         struct ecryptfs_crypt_stat *crypt_stat =
 185                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
 186         int rc = 0;
 187
 188         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 189                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 190                                                       PAGE_SIZE,
 191                                                       page->mapping->host);
 192         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 193                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 194                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 195                                                                     crypt_stat);
 196                         if (rc) {
 197                                 printk(KERN_ERR "%s: Error attempting to copy "
 198                                        "the encrypted content from the lower "
 199                                        "file whilst inserting the metadata "
 200                                        "from the xattr into the header; rc = "
 201                                        "[%d]\n", __func__, rc);
 202                                 goto out;
 203                         }
 204
 205                 } else {
 206                         rc = ecryptfs_read_lower_page_segment(
 207                                 page, page->index, 0, PAGE_SIZE,
 208                                 page->mapping->host);
 209                         if (rc) {
 210                                 printk(KERN_ERR "Error reading page; rc = "
 211                                        "[%d]\n", rc);
 212                                 goto out;
 213                         }
 214                 }
 215         } else {
 216                 rc = ecryptfs_decrypt_page(page);
 217                 if (rc) {
 218                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 219                                         "rc = [%d]\n", rc);
 220                         goto out;
 221                 }
 222         }
 223 out:
 224         if (rc)
 225                 ClearPageUptodate(page);
 226         else
 227                 SetPageUptodate(page);
 228         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
 229                         page->index);
 230         unlock_page(page);
 231         return rc;
 232 }
 233
 234 /*
 235  * Called with lower inode mutex held.
 236  */
 237 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 238 {
 239         struct inode *inode = page->mapping->host;
 240         int end_byte_in_page;
 241
 242         if ((i_size_read(inode) / PAGE_SIZE) != page->index)
 243                 goto out;
 244         end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
 245         if (to > end_byte_in_page)
 246                 end_byte_in_page = to;
 247         zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
 248 out:
 249         return 0;
 250 }
 251
 252 /**
 253  * ecryptfs_write_begin
 254  * @file: The eCryptfs file
 255  * @mapping: The eCryptfs object
 256  * @pos: The file offset at which to start writing
 257  * @len: Length of the write
 258  * @flags: Various flags
 259  * @pagep: Pointer to return the page
 260  * @fsdata: Pointer to return fs data (unused)
 261  *
 262  * This function must zero any hole we create
 263  *
 264  * Returns zero on success; non-zero otherwise
 265  */
 266 static int ecryptfs_write_begin(struct file *file,
 267                         struct address_space *mapping,
 268                         loff_t pos, unsigned len,
 269                         struct page **pagep, void **fsdata)
 270 {
 271         pgoff_t index = pos >> PAGE_SHIFT;
 272         struct page *page;
 273         loff_t prev_page_end_size;
 274         int rc = 0;
 275
 276         page = grab_cache_page_write_begin(mapping, index);
 277         if (!page)
 278                 return -ENOMEM;
 279         *pagep = page;
 280
 281         prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
 282         if (!PageUptodate(page)) {
 283                 struct ecryptfs_crypt_stat *crypt_stat =
 284                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
 285
 286                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 287                         rc = ecryptfs_read_lower_page_segment(
 288                                 page, index, 0, PAGE_SIZE, mapping->host);
 289                         if (rc) {
 290                                 printk(KERN_ERR "%s: Error attempting to read "
 291                                        "lower page segment; rc = [%d]\n",
 292                                        __func__, rc);
 293                                 ClearPageUptodate(page);
 294                                 goto out;
 295                         } else
 296                                 SetPageUptodate(page);
 297                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 298                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 299                                 rc = ecryptfs_copy_up_encrypted_with_header(
 300                                         page, crypt_stat);
 301                                 if (rc) {
 302                                         printk(KERN_ERR "%s: Error attempting "
 303                                                "to copy the encrypted content "
 304                                                "from the lower file whilst "
 305                                                "inserting the metadata from "
 306                                                "the xattr into the header; rc "
 307                                                "= [%d]\n", __func__, rc);
 308                                         ClearPageUptodate(page);
 309                                         goto out;
 310                                 }
 311                                 SetPageUptodate(page);
 312                         } else {
 313                                 rc = ecryptfs_read_lower_page_segment(
 314                                         page, index, 0, PAGE_SIZE,
 315                                         mapping->host);
 316                                 if (rc) {
 317                                         printk(KERN_ERR "%s: Error reading "
 318                                                "page; rc = [%d]\n",
 319                                                __func__, rc);
 320                                         ClearPageUptodate(page);
 321                                         goto out;
 322                                 }
 323                                 SetPageUptodate(page);
 324                         }
 325                 } else {
 326                         if (prev_page_end_size
 327                             >= i_size_read(page->mapping->host)) {
 328                                 zero_user(page, 0, PAGE_SIZE);
 329                                 SetPageUptodate(page);
 330                         } else if (len < PAGE_SIZE) {
 331                                 rc = ecryptfs_decrypt_page(page);
 332                                 if (rc) {
 333                                         printk(KERN_ERR "%s: Error decrypting "
 334                                                "page at index [%ld]; "
 335                                                "rc = [%d]\n",
 336                                                __func__, page->index, rc);
 337                                         ClearPageUptodate(page);
 338                                         goto out;
 339                                 }
 340                                 SetPageUptodate(page);
 341                         }
 342                 }
 343         }
 344         /* If creating a page or more of holes, zero them out via truncate.
 345          * Note, this will increase i_size. */
 346         if (index != 0) {
 347                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 348                         rc = ecryptfs_truncate(file->f_path.dentry,
 349                                                prev_page_end_size);
 350                         if (rc) {
 351                                 printk(KERN_ERR "%s: Error on attempt to "
 352                                        "truncate to (higher) offset [%lld];"
 353                                        " rc = [%d]\n", __func__,
 354                                        prev_page_end_size, rc);
 355                                 goto out;
 356                         }
 357                 }
 358         }
 359         /* Writing to a new page, and creating a small hole from start
 360          * of page?  Zero it out. */
 361         if ((i_size_read(mapping->host) == prev_page_end_size)
 362             && (pos != 0))
 363                 zero_user(page, 0, PAGE_SIZE);
 364 out:
 365         if (unlikely(rc)) {
 366                 unlock_page(page);
 367                 put_page(page);
 368                 *pagep = NULL;
 369         }
 370         return rc;
 371 }
 372
 373 /*
 374  * ecryptfs_write_inode_size_to_header
 375  *
 376  * Writes the lower file size to the first 8 bytes of the header.
 377  *
 378  * Returns zero on success; non-zero on error.
 379  */
 380 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 381 {
 382         char *file_size_virt;
 383         int rc;
 384
 385         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 386         if (!file_size_virt) {
 387                 rc = -ENOMEM;
 388                 goto out;
 389         }
 390         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 391         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 392                                   sizeof(u64));
 393         kfree(file_size_virt);
 394         if (rc < 0)
 395                 printk(KERN_ERR "%s: Error writing file size to header; "
 396                        "rc = [%d]\n", __func__, rc);
 397         else
 398                 rc = 0;
 399 out:
 400         return rc;
 401 }
 402
 403 struct kmem_cache *ecryptfs_xattr_cache;
 404
 405 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 406 {
 407         ssize_t size;
 408         void *xattr_virt;
 409         struct dentry *lower_dentry =
 410                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
 411         struct inode *lower_inode = d_inode(lower_dentry);
 412         int rc;
 413
 414         if (!(lower_inode->i_opflags & IOP_XATTR)) {
 415                 printk(KERN_WARNING
 416                        "No support for setting xattr in lower filesystem\n");
 417                 rc = -ENOSYS;
 418                 goto out;
 419         }
 420         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 421         if (!xattr_virt) {
 422                 rc = -ENOMEM;
 423                 goto out;
 424         }
 425         inode_lock(lower_inode);
 426         size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
 427                               xattr_virt, PAGE_SIZE);
 428         if (size < 0)
 429                 size = 8;
 430         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 431         rc = __vfs_setxattr(&init_user_ns, lower_dentry, lower_inode,
 432                             ECRYPTFS_XATTR_NAME, xattr_virt, size, 0);
 433         inode_unlock(lower_inode);
 434         if (rc)
 435                 printk(KERN_ERR "Error whilst attempting to write inode size "
 436                        "to lower file xattr; rc = [%d]\n", rc);
 437         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 438 out:
 439         return rc;
 440 }
 441
 442 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 443 {
 444         struct ecryptfs_crypt_stat *crypt_stat;
 445
 446         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 447         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 448         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 449                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 450         else
 451                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 452 }
 453
 454 /**
 455  * ecryptfs_write_end
 456  * @file: The eCryptfs file object
 457  * @mapping: The eCryptfs object
 458  * @pos: The file position
 459  * @len: The length of the data (unused)
 460  * @copied: The amount of data copied
 461  * @page: The eCryptfs page
 462  * @fsdata: The fsdata (unused)
 463  */
 464 static int ecryptfs_write_end(struct file *file,
 465                         struct address_space *mapping,
 466                         loff_t pos, unsigned len, unsigned copied,
 467                         struct page *page, void *fsdata)
 468 {
 469         pgoff_t index = pos >> PAGE_SHIFT;
 470         unsigned from = pos & (PAGE_SIZE - 1);
 471         unsigned to = from + copied;
 472         struct inode *ecryptfs_inode = mapping->host;
 473         struct ecryptfs_crypt_stat *crypt_stat =
 474                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 475         int rc;
 476
 477         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 478                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 479         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 480                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 481                                                        to);
 482                 if (!rc) {
 483                         rc = copied;
 484                         fsstack_copy_inode_size(ecryptfs_inode,
 485                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 486                 }
 487                 goto out;
 488         }
 489         if (!PageUptodate(page)) {
 490                 if (copied < PAGE_SIZE) {
 491                         rc = 0;
 492                         goto out;
 493                 }
 494                 SetPageUptodate(page);
 495         }
 496         /* Fills in zeros if 'to' goes beyond inode size */
 497         rc = fill_zeros_to_end_of_page(page, to);
 498         if (rc) {
 499                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 500                         "zeros in page with index = [0x%.16lx]\n", index);
 501                 goto out;
 502         }
 503         rc = ecryptfs_encrypt_page(page);
 504         if (rc) {
 505                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 506                                 "index [0x%.16lx])\n", index);
 507                 goto out;
 508         }
 509         if (pos + copied > i_size_read(ecryptfs_inode)) {
 510                 i_size_write(ecryptfs_inode, pos + copied);
 511                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 512                         "[0x%.16llx]\n",
 513                         (unsigned long long)i_size_read(ecryptfs_inode));
 514         }
 515         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 516         if (rc)
 517                 printk(KERN_ERR "Error writing inode size to metadata; "
 518                        "rc = [%d]\n", rc);
 519         else
 520                 rc = copied;
 521 out:
 522         unlock_page(page);
 523         put_page(page);
 524         return rc;
 525 }
 526
 527 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 528 {
 529         struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
 530         int ret = bmap(lower_inode, &block);
 531
 532         if (ret)
 533                 return 0;
 534         return block;
 535 }
 536
 537 #include <linux/buffer_head.h>
 538
 539 const struct address_space_operations ecryptfs_aops = {
 540         /*
 541          * XXX: This is pretty broken for multiple reasons: ecryptfs does not
 542          * actually use buffer_heads, and ecryptfs will crash without
 543          * CONFIG_BLOCK.  But it matches the behavior before the default for
 544          * address_space_operations without the ->dirty_folio method was
 545          * cleaned up, so this is the best we can do without maintainer
 546          * feedback.
 547          */
 548 #ifdef CONFIG_BLOCK
 549         .dirty_folio    = block_dirty_folio,
 550         .invalidate_folio = block_invalidate_folio,
 551 #endif
 552         .writepage = ecryptfs_writepage,
 553         .read_folio = ecryptfs_read_folio,
 554         .write_begin = ecryptfs_write_begin,
 555         .write_end = ecryptfs_write_end,
 556         .bmap = ecryptfs_bmap,
 557 };