fs/ecryptfs/mmap.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  * This is where eCryptfs coordinates the symmetric encryption and
   4  * decryption of the file data as it passes between the lower
   5  * encrypted file and the upper decrypted file.
   6  *
   7  * Copyright (C) 1997-2003 Erez Zadok
   8  * Copyright (C) 2001-2003 Stony Brook University
   9  * Copyright (C) 2004-2007 International Business Machines Corp.
  10  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
  11  *
  12  * This program is free software; you can redistribute it and/or
  13  * modify it under the terms of the GNU General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  25  * 02111-1307, USA.
  26  */
  27
  28 #include <linux/pagemap.h>
  29 #include <linux/writeback.h>
  30 #include <linux/page-flags.h>
  31 #include <linux/mount.h>
  32 #include <linux/file.h>
  33 #include <linux/scatterlist.h>
  34 #include <linux/slab.h>
  35 #include <asm/unaligned.h>
  36 #include "ecryptfs_kernel.h"
  37
  38 /**
  39  * ecryptfs_get_locked_page
  40  *
  41  * Get one page from cache or lower f/s, return error otherwise.
  42  *
  43  * Returns locked and up-to-date page (if ok), with increased
  44  * refcnt.
  45  */
  46 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
  47 {
  48         struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
  49         if (!IS_ERR(page))
  50                 lock_page(page);
  51         return page;
  52 }
  53
  54 /**
  55  * ecryptfs_writepage
  56  * @page: Page that is locked before this call is made
  57  *
  58  * Returns zero on success; non-zero otherwise
  59  *
  60  * This is where we encrypt the data and pass the encrypted data to
  61  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
  62  * entire underlying packets.
  63  */
  64 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  65 {
  66         int rc;
  67
  68         rc = ecryptfs_encrypt_page(page);
  69         if (rc) {
  70                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  71                                 "page (upper index [0x%.16lx])\n", page->index);
  72                 ClearPageUptodate(page);
  73                 goto out;
  74         }
  75         SetPageUptodate(page);
  76 out:
  77         unlock_page(page);
  78         return rc;
  79 }
  80
  81 static void strip_xattr_flag(char *page_virt,
  82                              struct ecryptfs_crypt_stat *crypt_stat)
  83 {
  84         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  85                 size_t written;
  86
  87                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  88                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  89                                                 &written);
  90                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  91         }
  92 }
  93
  94 /**
  95  *   Header Extent:
  96  *     Octets 0-7:        Unencrypted file size (big-endian)
  97  *     Octets 8-15:       eCryptfs special marker
  98  *     Octets 16-19:      Flags
  99  *      Octet 16:         File format version number (between 0 and 255)
 100  *      Octets 17-18:     Reserved
 101  *      Octet 19:         Bit 1 (lsb): Reserved
 102  *                        Bit 2: Encrypted?
 103  *                        Bits 3-8: Reserved
 104  *     Octets 20-23:      Header extent size (big-endian)
 105  *     Octets 24-25:      Number of header extents at front of file
 106  *                        (big-endian)
 107  *     Octet  26:         Begin RFC 2440 authentication token packet set
 108  */
 109
 110 /**
 111  * ecryptfs_copy_up_encrypted_with_header
 112  * @page: Sort of a ``virtual'' representation of the encrypted lower
 113  *        file. The actual lower file does not have the metadata in
 114  *        the header. This is locked.
 115  * @crypt_stat: The eCryptfs inode's cryptographic context
 116  *
 117  * The ``view'' is the version of the file that userspace winds up
 118  * seeing, with the header information inserted.
 119  */
 120 static int
 121 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 122                                        struct ecryptfs_crypt_stat *crypt_stat)
 123 {
 124         loff_t extent_num_in_page = 0;
 125         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 126                                        / crypt_stat->extent_size);
 127         int rc = 0;
 128
 129         while (extent_num_in_page < num_extents_per_page) {
 130                 loff_t view_extent_num = ((((loff_t)page->index)
 131                                            * num_extents_per_page)
 132                                           + extent_num_in_page);
 133                 size_t num_header_extents_at_front =
 134                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 135
 136                 if (view_extent_num < num_header_extents_at_front) {
 137                         /* This is a header extent */
 138                         char *page_virt;
 139
 140                         page_virt = kmap_atomic(page);
 141                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 142                         /* TODO: Support more than one header extent */
 143                         if (view_extent_num == 0) {
 144                                 size_t written;
 145
 146                                 rc = ecryptfs_read_xattr_region(
 147                                         page_virt, page->mapping->host);
 148                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 149                                 ecryptfs_write_header_metadata(page_virt + 20,
 150                                                                crypt_stat,
 151                                                                &written);
 152                         }
 153                         kunmap_atomic(page_virt);
 154                         flush_dcache_page(page);
 155                         if (rc) {
 156                                 printk(KERN_ERR "%s: Error reading xattr "
 157                                        "region; rc = [%d]\n", __func__, rc);
 158                                 goto out;
 159                         }
 160                 } else {
 161                         /* This is an encrypted data extent */
 162                         loff_t lower_offset =
 163                                 ((view_extent_num * crypt_stat->extent_size)
 164                                  - crypt_stat->metadata_size);
 165
 166                         rc = ecryptfs_read_lower_page_segment(
 167                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 168                                 (lower_offset & ~PAGE_CACHE_MASK),
 169                                 crypt_stat->extent_size, page->mapping->host);
 170                         if (rc) {
 171                                 printk(KERN_ERR "%s: Error attempting to read "
 172                                        "extent at offset [%lld] in the lower "
 173                                        "file; rc = [%d]\n", __func__,
 174                                        lower_offset, rc);
 175                                 goto out;
 176                         }
 177                 }
 178                 extent_num_in_page++;
 179         }
 180 out:
 181         return rc;
 182 }
 183
 184 /**
 185  * ecryptfs_readpage
 186  * @file: An eCryptfs file
 187  * @page: Page from eCryptfs inode mapping into which to stick the read data
 188  *
 189  * Read in a page, decrypting if necessary.
 190  *
 191  * Returns zero on success; non-zero on error.
 192  */
 193 static int ecryptfs_readpage(struct file *file, struct page *page)
 194 {
 195         struct ecryptfs_crypt_stat *crypt_stat =
 196                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
 197         int rc = 0;
 198
 199         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 200                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 201                                                       PAGE_CACHE_SIZE,
 202                                                       page->mapping->host);
 203         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 204                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 205                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 206                                                                     crypt_stat);
 207                         if (rc) {
 208                                 printk(KERN_ERR "%s: Error attempting to copy "
 209                                        "the encrypted content from the lower "
 210                                        "file whilst inserting the metadata "
 211                                        "from the xattr into the header; rc = "
 212                                        "[%d]\n", __func__, rc);
 213                                 goto out;
 214                         }
 215
 216                 } else {
 217                         rc = ecryptfs_read_lower_page_segment(
 218                                 page, page->index, 0, PAGE_CACHE_SIZE,
 219                                 page->mapping->host);
 220                         if (rc) {
 221                                 printk(KERN_ERR "Error reading page; rc = "
 222                                        "[%d]\n", rc);
 223                                 goto out;
 224                         }
 225                 }
 226         } else {
 227                 rc = ecryptfs_decrypt_page(page);
 228                 if (rc) {
 229                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 230                                         "rc = [%d]\n", rc);
 231                         goto out;
 232                 }
 233         }
 234 out:
 235         if (rc)
 236                 ClearPageUptodate(page);
 237         else
 238                 SetPageUptodate(page);
 239         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
 240                         page->index);
 241         unlock_page(page);
 242         return rc;
 243 }
 244
 245 /**
 246  * Called with lower inode mutex held.
 247  */
 248 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 249 {
 250         struct inode *inode = page->mapping->host;
 251         int end_byte_in_page;
 252
 253         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 254                 goto out;
 255         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 256         if (to > end_byte_in_page)
 257                 end_byte_in_page = to;
 258         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
 259 out:
 260         return 0;
 261 }
 262
 263 /**
 264  * ecryptfs_write_begin
 265  * @file: The eCryptfs file
 266  * @mapping: The eCryptfs object
 267  * @pos: The file offset at which to start writing
 268  * @len: Length of the write
 269  * @flags: Various flags
 270  * @pagep: Pointer to return the page
 271  * @fsdata: Pointer to return fs data (unused)
 272  *
 273  * This function must zero any hole we create
 274  *
 275  * Returns zero on success; non-zero otherwise
 276  */
 277 static int ecryptfs_write_begin(struct file *file,
 278                         struct address_space *mapping,
 279                         loff_t pos, unsigned len, unsigned flags,
 280                         struct page **pagep, void **fsdata)
 281 {
 282         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 283         struct page *page;
 284         loff_t prev_page_end_size;
 285         int rc = 0;
 286
 287         page = grab_cache_page_write_begin(mapping, index, flags);
 288         if (!page)
 289                 return -ENOMEM;
 290         *pagep = page;
 291
 292         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
 293         if (!PageUptodate(page)) {
 294                 struct ecryptfs_crypt_stat *crypt_stat =
 295                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
 296
 297                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 298                         rc = ecryptfs_read_lower_page_segment(
 299                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
 300                         if (rc) {
 301                                 printk(KERN_ERR "%s: Error attempting to read "
 302                                        "lower page segment; rc = [%d]\n",
 303                                        __func__, rc);
 304                                 ClearPageUptodate(page);
 305                                 goto out;
 306                         } else
 307                                 SetPageUptodate(page);
 308                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 309                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 310                                 rc = ecryptfs_copy_up_encrypted_with_header(
 311                                         page, crypt_stat);
 312                                 if (rc) {
 313                                         printk(KERN_ERR "%s: Error attempting "
 314                                                "to copy the encrypted content "
 315                                                "from the lower file whilst "
 316                                                "inserting the metadata from "
 317                                                "the xattr into the header; rc "
 318                                                "= [%d]\n", __func__, rc);
 319                                         ClearPageUptodate(page);
 320                                         goto out;
 321                                 }
 322                                 SetPageUptodate(page);
 323                         } else {
 324                                 rc = ecryptfs_read_lower_page_segment(
 325                                         page, index, 0, PAGE_CACHE_SIZE,
 326                                         mapping->host);
 327                                 if (rc) {
 328                                         printk(KERN_ERR "%s: Error reading "
 329                                                "page; rc = [%d]\n",
 330                                                __func__, rc);
 331                                         ClearPageUptodate(page);
 332                                         goto out;
 333                                 }
 334                                 SetPageUptodate(page);
 335                         }
 336                 } else {
 337                         if (prev_page_end_size
 338                             >= i_size_read(page->mapping->host)) {
 339                                 zero_user(page, 0, PAGE_CACHE_SIZE);
 340                                 SetPageUptodate(page);
 341                         } else if (len < PAGE_CACHE_SIZE) {
 342                                 rc = ecryptfs_decrypt_page(page);
 343                                 if (rc) {
 344                                         printk(KERN_ERR "%s: Error decrypting "
 345                                                "page at index [%ld]; "
 346                                                "rc = [%d]\n",
 347                                                __func__, page->index, rc);
 348                                         ClearPageUptodate(page);
 349                                         goto out;
 350                                 }
 351                                 SetPageUptodate(page);
 352                         }
 353                 }
 354         }
 355         /* If creating a page or more of holes, zero them out via truncate.
 356          * Note, this will increase i_size. */
 357         if (index != 0) {
 358                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 359                         rc = ecryptfs_truncate(file->f_path.dentry,
 360                                                prev_page_end_size);
 361                         if (rc) {
 362                                 printk(KERN_ERR "%s: Error on attempt to "
 363                                        "truncate to (higher) offset [%lld];"
 364                                        " rc = [%d]\n", __func__,
 365                                        prev_page_end_size, rc);
 366                                 goto out;
 367                         }
 368                 }
 369         }
 370         /* Writing to a new page, and creating a small hole from start
 371          * of page?  Zero it out. */
 372         if ((i_size_read(mapping->host) == prev_page_end_size)
 373             && (pos != 0))
 374                 zero_user(page, 0, PAGE_CACHE_SIZE);
 375 out:
 376         if (unlikely(rc)) {
 377                 unlock_page(page);
 378                 page_cache_release(page);
 379                 *pagep = NULL;
 380         }
 381         return rc;
 382 }
 383
 384 /**
 385  * ecryptfs_write_inode_size_to_header
 386  *
 387  * Writes the lower file size to the first 8 bytes of the header.
 388  *
 389  * Returns zero on success; non-zero on error.
 390  */
 391 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 392 {
 393         char *file_size_virt;
 394         int rc;
 395
 396         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 397         if (!file_size_virt) {
 398                 rc = -ENOMEM;
 399                 goto out;
 400         }
 401         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 402         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 403                                   sizeof(u64));
 404         kfree(file_size_virt);
 405         if (rc < 0)
 406                 printk(KERN_ERR "%s: Error writing file size to header; "
 407                        "rc = [%d]\n", __func__, rc);
 408         else
 409                 rc = 0;
 410 out:
 411         return rc;
 412 }
 413
 414 struct kmem_cache *ecryptfs_xattr_cache;
 415
 416 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 417 {
 418         ssize_t size;
 419         void *xattr_virt;
 420         struct dentry *lower_dentry =
 421                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
 422         struct inode *lower_inode = d_inode(lower_dentry);
 423         int rc;
 424
 425         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 426                 printk(KERN_WARNING
 427                        "No support for setting xattr in lower filesystem\n");
 428                 rc = -ENOSYS;
 429                 goto out;
 430         }
 431         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 432         if (!xattr_virt) {
 433                 printk(KERN_ERR "Out of memory whilst attempting to write "
 434                        "inode size to xattr\n");
 435                 rc = -ENOMEM;
 436                 goto out;
 437         }
 438         inode_lock(lower_inode);
 439         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 440                                            xattr_virt, PAGE_CACHE_SIZE);
 441         if (size < 0)
 442                 size = 8;
 443         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 444         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 445                                          xattr_virt, size, 0);
 446         inode_unlock(lower_inode);
 447         if (rc)
 448                 printk(KERN_ERR "Error whilst attempting to write inode size "
 449                        "to lower file xattr; rc = [%d]\n", rc);
 450         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 451 out:
 452         return rc;
 453 }
 454
 455 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 456 {
 457         struct ecryptfs_crypt_stat *crypt_stat;
 458
 459         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 460         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 461         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 462                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 463         else
 464                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 465 }
 466
 467 /**
 468  * ecryptfs_write_end
 469  * @file: The eCryptfs file object
 470  * @mapping: The eCryptfs object
 471  * @pos: The file position
 472  * @len: The length of the data (unused)
 473  * @copied: The amount of data copied
 474  * @page: The eCryptfs page
 475  * @fsdata: The fsdata (unused)
 476  */
 477 static int ecryptfs_write_end(struct file *file,
 478                         struct address_space *mapping,
 479                         loff_t pos, unsigned len, unsigned copied,
 480                         struct page *page, void *fsdata)
 481 {
 482         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 483         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 484         unsigned to = from + copied;
 485         struct inode *ecryptfs_inode = mapping->host;
 486         struct ecryptfs_crypt_stat *crypt_stat =
 487                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 488         int rc;
 489
 490         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 491                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 492         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 493                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 494                                                        to);
 495                 if (!rc) {
 496                         rc = copied;
 497                         fsstack_copy_inode_size(ecryptfs_inode,
 498                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 499                 }
 500                 goto out;
 501         }
 502         if (!PageUptodate(page)) {
 503                 if (copied < PAGE_CACHE_SIZE) {
 504                         rc = 0;
 505                         goto out;
 506                 }
 507                 SetPageUptodate(page);
 508         }
 509         /* Fills in zeros if 'to' goes beyond inode size */
 510         rc = fill_zeros_to_end_of_page(page, to);
 511         if (rc) {
 512                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 513                         "zeros in page with index = [0x%.16lx]\n", index);
 514                 goto out;
 515         }
 516         rc = ecryptfs_encrypt_page(page);
 517         if (rc) {
 518                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 519                                 "index [0x%.16lx])\n", index);
 520                 goto out;
 521         }
 522         if (pos + copied > i_size_read(ecryptfs_inode)) {
 523                 i_size_write(ecryptfs_inode, pos + copied);
 524                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 525                         "[0x%.16llx]\n",
 526                         (unsigned long long)i_size_read(ecryptfs_inode));
 527         }
 528         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 529         if (rc)
 530                 printk(KERN_ERR "Error writing inode size to metadata; "
 531                        "rc = [%d]\n", rc);
 532         else
 533                 rc = copied;
 534 out:
 535         unlock_page(page);
 536         page_cache_release(page);
 537         return rc;
 538 }
 539
 540 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 541 {
 542         int rc = 0;
 543         struct inode *inode;
 544         struct inode *lower_inode;
 545
 546         inode = (struct inode *)mapping->host;
 547         lower_inode = ecryptfs_inode_to_lower(inode);
 548         if (lower_inode->i_mapping->a_ops->bmap)
 549                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 550                                                          block);
 551         return rc;
 552 }
 553
 554 const struct address_space_operations ecryptfs_aops = {
 555         .writepage = ecryptfs_writepage,
 556         .readpage = ecryptfs_readpage,
 557         .write_begin = ecryptfs_write_begin,
 558         .write_end = ecryptfs_write_end,
 559         .bmap = ecryptfs_bmap,
 560 };