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 <mahalcro@us.ibm.com>
  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_readpage
 174  * @file: An eCryptfs file
 175  * @page: Page from eCryptfs inode mapping into which to stick the read data
 176  *
 177  * Read in a page, decrypting if necessary.
 178  *
 179  * Returns zero on success; non-zero on error.
 180  */
 181 static int ecryptfs_readpage(struct file *file, struct page *page)
 182 {
 183         struct ecryptfs_crypt_stat *crypt_stat =
 184                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
 185         int rc = 0;
 186
 187         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 188                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 189                                                       PAGE_SIZE,
 190                                                       page->mapping->host);
 191         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 192                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 193                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 194                                                                     crypt_stat);
 195                         if (rc) {
 196                                 printk(KERN_ERR "%s: Error attempting to copy "
 197                                        "the encrypted content from the lower "
 198                                        "file whilst inserting the metadata "
 199                                        "from the xattr into the header; rc = "
 200                                        "[%d]\n", __func__, rc);
 201                                 goto out;
 202                         }
 203
 204                 } else {
 205                         rc = ecryptfs_read_lower_page_segment(
 206                                 page, page->index, 0, PAGE_SIZE,
 207                                 page->mapping->host);
 208                         if (rc) {
 209                                 printk(KERN_ERR "Error reading page; rc = "
 210                                        "[%d]\n", rc);
 211                                 goto out;
 212                         }
 213                 }
 214         } else {
 215                 rc = ecryptfs_decrypt_page(page);
 216                 if (rc) {
 217                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 218                                         "rc = [%d]\n", rc);
 219                         goto out;
 220                 }
 221         }
 222 out:
 223         if (rc)
 224                 ClearPageUptodate(page);
 225         else
 226                 SetPageUptodate(page);
 227         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
 228                         page->index);
 229         unlock_page(page);
 230         return rc;
 231 }
 232
 233 /*
 234  * Called with lower inode mutex held.
 235  */
 236 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 237 {
 238         struct inode *inode = page->mapping->host;
 239         int end_byte_in_page;
 240
 241         if ((i_size_read(inode) / PAGE_SIZE) != page->index)
 242                 goto out;
 243         end_byte_in_page = i_size_read(inode) % PAGE_SIZE;
 244         if (to > end_byte_in_page)
 245                 end_byte_in_page = to;
 246         zero_user_segment(page, end_byte_in_page, PAGE_SIZE);
 247 out:
 248         return 0;
 249 }
 250
 251 /**
 252  * ecryptfs_write_begin
 253  * @file: The eCryptfs file
 254  * @mapping: The eCryptfs object
 255  * @pos: The file offset at which to start writing
 256  * @len: Length of the write
 257  * @flags: Various flags
 258  * @pagep: Pointer to return the page
 259  * @fsdata: Pointer to return fs data (unused)
 260  *
 261  * This function must zero any hole we create
 262  *
 263  * Returns zero on success; non-zero otherwise
 264  */
 265 static int ecryptfs_write_begin(struct file *file,
 266                         struct address_space *mapping,
 267                         loff_t pos, unsigned len, unsigned flags,
 268                         struct page **pagep, void **fsdata)
 269 {
 270         pgoff_t index = pos >> PAGE_SHIFT;
 271         struct page *page;
 272         loff_t prev_page_end_size;
 273         int rc = 0;
 274
 275         page = grab_cache_page_write_begin(mapping, index, flags);
 276         if (!page)
 277                 return -ENOMEM;
 278         *pagep = page;
 279
 280         prev_page_end_size = ((loff_t)index << PAGE_SHIFT);
 281         if (!PageUptodate(page)) {
 282                 struct ecryptfs_crypt_stat *crypt_stat =
 283                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
 284
 285                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 286                         rc = ecryptfs_read_lower_page_segment(
 287                                 page, index, 0, PAGE_SIZE, mapping->host);
 288                         if (rc) {
 289                                 printk(KERN_ERR "%s: Error attempting to read "
 290                                        "lower page segment; rc = [%d]\n",
 291                                        __func__, rc);
 292                                 ClearPageUptodate(page);
 293                                 goto out;
 294                         } else
 295                                 SetPageUptodate(page);
 296                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 297                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 298                                 rc = ecryptfs_copy_up_encrypted_with_header(
 299                                         page, crypt_stat);
 300                                 if (rc) {
 301                                         printk(KERN_ERR "%s: Error attempting "
 302                                                "to copy the encrypted content "
 303                                                "from the lower file whilst "
 304                                                "inserting the metadata from "
 305                                                "the xattr into the header; rc "
 306                                                "= [%d]\n", __func__, rc);
 307                                         ClearPageUptodate(page);
 308                                         goto out;
 309                                 }
 310                                 SetPageUptodate(page);
 311                         } else {
 312                                 rc = ecryptfs_read_lower_page_segment(
 313                                         page, index, 0, PAGE_SIZE,
 314                                         mapping->host);
 315                                 if (rc) {
 316                                         printk(KERN_ERR "%s: Error reading "
 317                                                "page; rc = [%d]\n",
 318                                                __func__, rc);
 319                                         ClearPageUptodate(page);
 320                                         goto out;
 321                                 }
 322                                 SetPageUptodate(page);
 323                         }
 324                 } else {
 325                         if (prev_page_end_size
 326                             >= i_size_read(page->mapping->host)) {
 327                                 zero_user(page, 0, PAGE_SIZE);
 328                                 SetPageUptodate(page);
 329                         } else if (len < PAGE_SIZE) {
 330                                 rc = ecryptfs_decrypt_page(page);
 331                                 if (rc) {
 332                                         printk(KERN_ERR "%s: Error decrypting "
 333                                                "page at index [%ld]; "
 334                                                "rc = [%d]\n",
 335                                                __func__, page->index, rc);
 336                                         ClearPageUptodate(page);
 337                                         goto out;
 338                                 }
 339                                 SetPageUptodate(page);
 340                         }
 341                 }
 342         }
 343         /* If creating a page or more of holes, zero them out via truncate.
 344          * Note, this will increase i_size. */
 345         if (index != 0) {
 346                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 347                         rc = ecryptfs_truncate(file->f_path.dentry,
 348                                                prev_page_end_size);
 349                         if (rc) {
 350                                 printk(KERN_ERR "%s: Error on attempt to "
 351                                        "truncate to (higher) offset [%lld];"
 352                                        " rc = [%d]\n", __func__,
 353                                        prev_page_end_size, rc);
 354                                 goto out;
 355                         }
 356                 }
 357         }
 358         /* Writing to a new page, and creating a small hole from start
 359          * of page?  Zero it out. */
 360         if ((i_size_read(mapping->host) == prev_page_end_size)
 361             && (pos != 0))
 362                 zero_user(page, 0, PAGE_SIZE);
 363 out:
 364         if (unlikely(rc)) {
 365                 unlock_page(page);
 366                 put_page(page);
 367                 *pagep = NULL;
 368         }
 369         return rc;
 370 }
 371
 372 /*
 373  * ecryptfs_write_inode_size_to_header
 374  *
 375  * Writes the lower file size to the first 8 bytes of the header.
 376  *
 377  * Returns zero on success; non-zero on error.
 378  */
 379 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 380 {
 381         char *file_size_virt;
 382         int rc;
 383
 384         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 385         if (!file_size_virt) {
 386                 rc = -ENOMEM;
 387                 goto out;
 388         }
 389         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 390         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 391                                   sizeof(u64));
 392         kfree(file_size_virt);
 393         if (rc < 0)
 394                 printk(KERN_ERR "%s: Error writing file size to header; "
 395                        "rc = [%d]\n", __func__, rc);
 396         else
 397                 rc = 0;
 398 out:
 399         return rc;
 400 }
 401
 402 struct kmem_cache *ecryptfs_xattr_cache;
 403
 404 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 405 {
 406         ssize_t size;
 407         void *xattr_virt;
 408         struct dentry *lower_dentry =
 409                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
 410         struct inode *lower_inode = d_inode(lower_dentry);
 411         int rc;
 412
 413         if (!(lower_inode->i_opflags & IOP_XATTR)) {
 414                 printk(KERN_WARNING
 415                        "No support for setting xattr in lower filesystem\n");
 416                 rc = -ENOSYS;
 417                 goto out;
 418         }
 419         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 420         if (!xattr_virt) {
 421                 rc = -ENOMEM;
 422                 goto out;
 423         }
 424         inode_lock(lower_inode);
 425         size = __vfs_getxattr(lower_dentry, lower_inode, ECRYPTFS_XATTR_NAME,
 426                               xattr_virt, PAGE_SIZE);
 427         if (size < 0)
 428                 size = 8;
 429         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 430         rc = __vfs_setxattr(&init_user_ns, lower_dentry, lower_inode,
 431                             ECRYPTFS_XATTR_NAME, xattr_virt, size, 0);
 432         inode_unlock(lower_inode);
 433         if (rc)
 434                 printk(KERN_ERR "Error whilst attempting to write inode size "
 435                        "to lower file xattr; rc = [%d]\n", rc);
 436         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 437 out:
 438         return rc;
 439 }
 440
 441 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 442 {
 443         struct ecryptfs_crypt_stat *crypt_stat;
 444
 445         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 446         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 447         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 448                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 449         else
 450                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 451 }
 452
 453 /**
 454  * ecryptfs_write_end
 455  * @file: The eCryptfs file object
 456  * @mapping: The eCryptfs object
 457  * @pos: The file position
 458  * @len: The length of the data (unused)
 459  * @copied: The amount of data copied
 460  * @page: The eCryptfs page
 461  * @fsdata: The fsdata (unused)
 462  */
 463 static int ecryptfs_write_end(struct file *file,
 464                         struct address_space *mapping,
 465                         loff_t pos, unsigned len, unsigned copied,
 466                         struct page *page, void *fsdata)
 467 {
 468         pgoff_t index = pos >> PAGE_SHIFT;
 469         unsigned from = pos & (PAGE_SIZE - 1);
 470         unsigned to = from + copied;
 471         struct inode *ecryptfs_inode = mapping->host;
 472         struct ecryptfs_crypt_stat *crypt_stat =
 473                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 474         int rc;
 475
 476         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 477                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 478         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 479                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 480                                                        to);
 481                 if (!rc) {
 482                         rc = copied;
 483                         fsstack_copy_inode_size(ecryptfs_inode,
 484                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 485                 }
 486                 goto out;
 487         }
 488         if (!PageUptodate(page)) {
 489                 if (copied < PAGE_SIZE) {
 490                         rc = 0;
 491                         goto out;
 492                 }
 493                 SetPageUptodate(page);
 494         }
 495         /* Fills in zeros if 'to' goes beyond inode size */
 496         rc = fill_zeros_to_end_of_page(page, to);
 497         if (rc) {
 498                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 499                         "zeros in page with index = [0x%.16lx]\n", index);
 500                 goto out;
 501         }
 502         rc = ecryptfs_encrypt_page(page);
 503         if (rc) {
 504                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 505                                 "index [0x%.16lx])\n", index);
 506                 goto out;
 507         }
 508         if (pos + copied > i_size_read(ecryptfs_inode)) {
 509                 i_size_write(ecryptfs_inode, pos + copied);
 510                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 511                         "[0x%.16llx]\n",
 512                         (unsigned long long)i_size_read(ecryptfs_inode));
 513         }
 514         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 515         if (rc)
 516                 printk(KERN_ERR "Error writing inode size to metadata; "
 517                        "rc = [%d]\n", rc);
 518         else
 519                 rc = copied;
 520 out:
 521         unlock_page(page);
 522         put_page(page);
 523         return rc;
 524 }
 525
 526 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 527 {
 528         struct inode *lower_inode = ecryptfs_inode_to_lower(mapping->host);
 529         int ret = bmap(lower_inode, &block);
 530
 531         if (ret)
 532                 return 0;
 533         return block;
 534 }
 535
 536 #include <linux/buffer_head.h>
 537
 538 const struct address_space_operations ecryptfs_aops = {
 539         /*
 540          * XXX: This is pretty broken for multiple reasons: ecryptfs does not
 541          * actually use buffer_heads, and ecryptfs will crash without
 542          * CONFIG_BLOCK.  But it matches the behavior before the default for
 543          * address_space_operations without the ->set_page_dirty method was
 544          * cleaned up, so this is the best we can do without maintainer
 545          * feedback.
 546          */
 547 #ifdef CONFIG_BLOCK
 548         .set_page_dirty = __set_page_dirty_buffers,
 549 #endif
 550         .writepage = ecryptfs_writepage,
 551         .readpage = ecryptfs_readpage,
 552         .write_begin = ecryptfs_write_begin,
 553         .write_end = ecryptfs_write_end,
 554         .bmap = ecryptfs_bmap,
 555 };