kernel/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/crypto.h>
  34 #include <linux/scatterlist.h>
  35 #include <linux/slab.h>
  36 #include <asm/unaligned.h>
  37 #include "ecryptfs_kernel.h"
  38
  39 /**
  40  * ecryptfs_get_locked_page
  41  *
  42  * Get one page from cache or lower f/s, return error otherwise.
  43  *
  44  * Returns locked and up-to-date page (if ok), with increased
  45  * refcnt.
  46  */
  47 struct page *ecryptfs_get_locked_page(struct inode *inode, loff_t index)
  48 {
  49         struct page *page = read_mapping_page(inode->i_mapping, index, NULL);
  50         if (!IS_ERR(page))
  51                 lock_page(page);
  52         return page;
  53 }
  54
  55 /**
  56  * ecryptfs_writepage
  57  * @page: Page that is locked before this call is made
  58  *
  59  * Returns zero on success; non-zero otherwise
  60  *
  61  * This is where we encrypt the data and pass the encrypted data to
  62  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
  63  * entire underlying packets.
  64  */
  65 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  66 {
  67         int rc;
  68
  69         rc = ecryptfs_encrypt_page(page);
  70         if (rc) {
  71                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  72                                 "page (upper index [0x%.16lx])\n", page->index);
  73                 ClearPageUptodate(page);
  74                 goto out;
  75         }
  76         SetPageUptodate(page);
  77 out:
  78         unlock_page(page);
  79         return rc;
  80 }
  81
  82 static void strip_xattr_flag(char *page_virt,
  83                              struct ecryptfs_crypt_stat *crypt_stat)
  84 {
  85         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  86                 size_t written;
  87
  88                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  89                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  90                                                 &written);
  91                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
  92         }
  93 }
  94
  95 /**
  96  *   Header Extent:
  97  *     Octets 0-7:        Unencrypted file size (big-endian)
  98  *     Octets 8-15:       eCryptfs special marker
  99  *     Octets 16-19:      Flags
 100  *      Octet 16:         File format version number (between 0 and 255)
 101  *      Octets 17-18:     Reserved
 102  *      Octet 19:         Bit 1 (lsb): Reserved
 103  *                        Bit 2: Encrypted?
 104  *                        Bits 3-8: Reserved
 105  *     Octets 20-23:      Header extent size (big-endian)
 106  *     Octets 24-25:      Number of header extents at front of file
 107  *                        (big-endian)
 108  *     Octet  26:         Begin RFC 2440 authentication token packet set
 109  */
 110
 111 /**
 112  * ecryptfs_copy_up_encrypted_with_header
 113  * @page: Sort of a ``virtual'' representation of the encrypted lower
 114  *        file. The actual lower file does not have the metadata in
 115  *        the header. This is locked.
 116  * @crypt_stat: The eCryptfs inode's cryptographic context
 117  *
 118  * The ``view'' is the version of the file that userspace winds up
 119  * seeing, with the header information inserted.
 120  */
 121 static int
 122 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 123                                        struct ecryptfs_crypt_stat *crypt_stat)
 124 {
 125         loff_t extent_num_in_page = 0;
 126         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 127                                        / crypt_stat->extent_size);
 128         int rc = 0;
 129
 130         while (extent_num_in_page < num_extents_per_page) {
 131                 loff_t view_extent_num = ((((loff_t)page->index)
 132                                            * num_extents_per_page)
 133                                           + extent_num_in_page);
 134                 size_t num_header_extents_at_front =
 135                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 136
 137                 if (view_extent_num < num_header_extents_at_front) {
 138                         /* This is a header extent */
 139                         char *page_virt;
 140
 141                         page_virt = kmap_atomic(page);
 142                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 143                         /* TODO: Support more than one header extent */
 144                         if (view_extent_num == 0) {
 145                                 size_t written;
 146
 147                                 rc = ecryptfs_read_xattr_region(
 148                                         page_virt, page->mapping->host);
 149                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 150                                 ecryptfs_write_header_metadata(page_virt + 20,
 151                                                                crypt_stat,
 152                                                                &written);
 153                         }
 154                         kunmap_atomic(page_virt);
 155                         flush_dcache_page(page);
 156                         if (rc) {
 157                                 printk(KERN_ERR "%s: Error reading xattr "
 158                                        "region; rc = [%d]\n", __func__, rc);
 159                                 goto out;
 160                         }
 161                 } else {
 162                         /* This is an encrypted data extent */
 163                         loff_t lower_offset =
 164                                 ((view_extent_num * crypt_stat->extent_size)
 165                                  - crypt_stat->metadata_size);
 166
 167                         rc = ecryptfs_read_lower_page_segment(
 168                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 169                                 (lower_offset & ~PAGE_CACHE_MASK),
 170                                 crypt_stat->extent_size, page->mapping->host);
 171                         if (rc) {
 172                                 printk(KERN_ERR "%s: Error attempting to read "
 173                                        "extent at offset [%lld] in the lower "
 174                                        "file; rc = [%d]\n", __func__,
 175                                        lower_offset, rc);
 176                                 goto out;
 177                         }
 178                 }
 179                 extent_num_in_page++;
 180         }
 181 out:
 182         return rc;
 183 }
 184
 185 /**
 186  * ecryptfs_readpage
 187  * @file: An eCryptfs file
 188  * @page: Page from eCryptfs inode mapping into which to stick the read data
 189  *
 190  * Read in a page, decrypting if necessary.
 191  *
 192  * Returns zero on success; non-zero on error.
 193  */
 194 static int ecryptfs_readpage(struct file *file, struct page *page)
 195 {
 196         struct ecryptfs_crypt_stat *crypt_stat =
 197                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
 198         int rc = 0;
 199
 200         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 201                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 202                                                       PAGE_CACHE_SIZE,
 203                                                       page->mapping->host);
 204         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 205                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 206                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 207                                                                     crypt_stat);
 208                         if (rc) {
 209                                 printk(KERN_ERR "%s: Error attempting to copy "
 210                                        "the encrypted content from the lower "
 211                                        "file whilst inserting the metadata "
 212                                        "from the xattr into the header; rc = "
 213                                        "[%d]\n", __func__, rc);
 214                                 goto out;
 215                         }
 216
 217                 } else {
 218                         rc = ecryptfs_read_lower_page_segment(
 219                                 page, page->index, 0, PAGE_CACHE_SIZE,
 220                                 page->mapping->host);
 221                         if (rc) {
 222                                 printk(KERN_ERR "Error reading page; rc = "
 223                                        "[%d]\n", rc);
 224                                 goto out;
 225                         }
 226                 }
 227         } else {
 228                 rc = ecryptfs_decrypt_page(page);
 229                 if (rc) {
 230                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 231                                         "rc = [%d]\n", rc);
 232                         goto out;
 233                 }
 234         }
 235 out:
 236         if (rc)
 237                 ClearPageUptodate(page);
 238         else
 239                 SetPageUptodate(page);
 240         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
 241                         page->index);
 242         unlock_page(page);
 243         return rc;
 244 }
 245
 246 /**
 247  * Called with lower inode mutex held.
 248  */
 249 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 250 {
 251         struct inode *inode = page->mapping->host;
 252         int end_byte_in_page;
 253
 254         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 255                 goto out;
 256         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 257         if (to > end_byte_in_page)
 258                 end_byte_in_page = to;
 259         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
 260 out:
 261         return 0;
 262 }
 263
 264 /**
 265  * ecryptfs_write_begin
 266  * @file: The eCryptfs file
 267  * @mapping: The eCryptfs object
 268  * @pos: The file offset at which to start writing
 269  * @len: Length of the write
 270  * @flags: Various flags
 271  * @pagep: Pointer to return the page
 272  * @fsdata: Pointer to return fs data (unused)
 273  *
 274  * This function must zero any hole we create
 275  *
 276  * Returns zero on success; non-zero otherwise
 277  */
 278 static int ecryptfs_write_begin(struct file *file,
 279                         struct address_space *mapping,
 280                         loff_t pos, unsigned len, unsigned flags,
 281                         struct page **pagep, void **fsdata)
 282 {
 283         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 284         struct page *page;
 285         loff_t prev_page_end_size;
 286         int rc = 0;
 287
 288         page = grab_cache_page_write_begin(mapping, index, flags);
 289         if (!page)
 290                 return -ENOMEM;
 291         *pagep = page;
 292
 293         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
 294         if (!PageUptodate(page)) {
 295                 struct ecryptfs_crypt_stat *crypt_stat =
 296                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
 297
 298                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 299                         rc = ecryptfs_read_lower_page_segment(
 300                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
 301                         if (rc) {
 302                                 printk(KERN_ERR "%s: Error attemping to read "
 303                                        "lower page segment; rc = [%d]\n",
 304                                        __func__, rc);
 305                                 ClearPageUptodate(page);
 306                                 goto out;
 307                         } else
 308                                 SetPageUptodate(page);
 309                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 310                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 311                                 rc = ecryptfs_copy_up_encrypted_with_header(
 312                                         page, crypt_stat);
 313                                 if (rc) {
 314                                         printk(KERN_ERR "%s: Error attempting "
 315                                                "to copy the encrypted content "
 316                                                "from the lower file whilst "
 317                                                "inserting the metadata from "
 318                                                "the xattr into the header; rc "
 319                                                "= [%d]\n", __func__, rc);
 320                                         ClearPageUptodate(page);
 321                                         goto out;
 322                                 }
 323                                 SetPageUptodate(page);
 324                         } else {
 325                                 rc = ecryptfs_read_lower_page_segment(
 326                                         page, index, 0, PAGE_CACHE_SIZE,
 327                                         mapping->host);
 328                                 if (rc) {
 329                                         printk(KERN_ERR "%s: Error reading "
 330                                                "page; rc = [%d]\n",
 331                                                __func__, rc);
 332                                         ClearPageUptodate(page);
 333                                         goto out;
 334                                 }
 335                                 SetPageUptodate(page);
 336                         }
 337                 } else {
 338                         if (prev_page_end_size
 339                             >= i_size_read(page->mapping->host)) {
 340                                 zero_user(page, 0, PAGE_CACHE_SIZE);
 341                                 SetPageUptodate(page);
 342                         } else if (len < PAGE_CACHE_SIZE) {
 343                                 rc = ecryptfs_decrypt_page(page);
 344                                 if (rc) {
 345                                         printk(KERN_ERR "%s: Error decrypting "
 346                                                "page at index [%ld]; "
 347                                                "rc = [%d]\n",
 348                                                __func__, page->index, rc);
 349                                         ClearPageUptodate(page);
 350                                         goto out;
 351                                 }
 352                                 SetPageUptodate(page);
 353                         }
 354                 }
 355         }
 356         /* If creating a page or more of holes, zero them out via truncate.
 357          * Note, this will increase i_size. */
 358         if (index != 0) {
 359                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 360                         rc = ecryptfs_truncate(file->f_path.dentry,
 361                                                prev_page_end_size);
 362                         if (rc) {
 363                                 printk(KERN_ERR "%s: Error on attempt to "
 364                                        "truncate to (higher) offset [%lld];"
 365                                        " rc = [%d]\n", __func__,
 366                                        prev_page_end_size, rc);
 367                                 goto out;
 368                         }
 369                 }
 370         }
 371         /* Writing to a new page, and creating a small hole from start
 372          * of page?  Zero it out. */
 373         if ((i_size_read(mapping->host) == prev_page_end_size)
 374             && (pos != 0))
 375                 zero_user(page, 0, PAGE_CACHE_SIZE);
 376 out:
 377         if (unlikely(rc)) {
 378                 unlock_page(page);
 379                 page_cache_release(page);
 380                 *pagep = NULL;
 381         }
 382         return rc;
 383 }
 384
 385 /**
 386  * ecryptfs_write_inode_size_to_header
 387  *
 388  * Writes the lower file size to the first 8 bytes of the header.
 389  *
 390  * Returns zero on success; non-zero on error.
 391  */
 392 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 393 {
 394         char *file_size_virt;
 395         int rc;
 396
 397         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 398         if (!file_size_virt) {
 399                 rc = -ENOMEM;
 400                 goto out;
 401         }
 402         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 403         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 404                                   sizeof(u64));
 405         kfree(file_size_virt);
 406         if (rc < 0)
 407                 printk(KERN_ERR "%s: Error writing file size to header; "
 408                        "rc = [%d]\n", __func__, rc);
 409         else
 410                 rc = 0;
 411 out:
 412         return rc;
 413 }
 414
 415 struct kmem_cache *ecryptfs_xattr_cache;
 416
 417 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 418 {
 419         ssize_t size;
 420         void *xattr_virt;
 421         struct dentry *lower_dentry =
 422                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_path.dentry;
 423         struct inode *lower_inode = d_inode(lower_dentry);
 424         int rc;
 425
 426         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 427                 printk(KERN_WARNING
 428                        "No support for setting xattr in lower filesystem\n");
 429                 rc = -ENOSYS;
 430                 goto out;
 431         }
 432         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 433         if (!xattr_virt) {
 434                 printk(KERN_ERR "Out of memory whilst attempting to write "
 435                        "inode size to xattr\n");
 436                 rc = -ENOMEM;
 437                 goto out;
 438         }
 439         mutex_lock(&lower_inode->i_mutex);
 440         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 441                                            xattr_virt, PAGE_CACHE_SIZE);
 442         if (size < 0)
 443                 size = 8;
 444         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 445         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 446                                          xattr_virt, size, 0);
 447         mutex_unlock(&lower_inode->i_mutex);
 448         if (rc)
 449                 printk(KERN_ERR "Error whilst attempting to write inode size "
 450                        "to lower file xattr; rc = [%d]\n", rc);
 451         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 452 out:
 453         return rc;
 454 }
 455
 456 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 457 {
 458         struct ecryptfs_crypt_stat *crypt_stat;
 459
 460         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 461         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 462         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 463                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 464         else
 465                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 466 }
 467
 468 /**
 469  * ecryptfs_write_end
 470  * @file: The eCryptfs file object
 471  * @mapping: The eCryptfs object
 472  * @pos: The file position
 473  * @len: The length of the data (unused)
 474  * @copied: The amount of data copied
 475  * @page: The eCryptfs page
 476  * @fsdata: The fsdata (unused)
 477  */
 478 static int ecryptfs_write_end(struct file *file,
 479                         struct address_space *mapping,
 480                         loff_t pos, unsigned len, unsigned copied,
 481                         struct page *page, void *fsdata)
 482 {
 483         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 484         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 485         unsigned to = from + copied;
 486         struct inode *ecryptfs_inode = mapping->host;
 487         struct ecryptfs_crypt_stat *crypt_stat =
 488                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 489         int rc;
 490
 491         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 492                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 493         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 494                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 495                                                        to);
 496                 if (!rc) {
 497                         rc = copied;
 498                         fsstack_copy_inode_size(ecryptfs_inode,
 499                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 500                 }
 501                 goto out;
 502         }
 503         if (!PageUptodate(page)) {
 504                 if (copied < PAGE_CACHE_SIZE) {
 505                         rc = 0;
 506                         goto out;
 507                 }
 508                 SetPageUptodate(page);
 509         }
 510         /* Fills in zeros if 'to' goes beyond inode size */
 511         rc = fill_zeros_to_end_of_page(page, to);
 512         if (rc) {
 513                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 514                         "zeros in page with index = [0x%.16lx]\n", index);
 515                 goto out;
 516         }
 517         rc = ecryptfs_encrypt_page(page);
 518         if (rc) {
 519                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 520                                 "index [0x%.16lx])\n", index);
 521                 goto out;
 522         }
 523         if (pos + copied > i_size_read(ecryptfs_inode)) {
 524                 i_size_write(ecryptfs_inode, pos + copied);
 525                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 526                         "[0x%.16llx]\n",
 527                         (unsigned long long)i_size_read(ecryptfs_inode));
 528         }
 529         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 530         if (rc)
 531                 printk(KERN_ERR "Error writing inode size to metadata; "
 532                        "rc = [%d]\n", rc);
 533         else
 534                 rc = copied;
 535 out:
 536         unlock_page(page);
 537         page_cache_release(page);
 538         return rc;
 539 }
 540
 541 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 542 {
 543         int rc = 0;
 544         struct inode *inode;
 545         struct inode *lower_inode;
 546
 547         inode = (struct inode *)mapping->host;
 548         lower_inode = ecryptfs_inode_to_lower(inode);
 549         if (lower_inode->i_mapping->a_ops->bmap)
 550                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 551                                                          block);
 552         return rc;
 553 }
 554
 555 const struct address_space_operations ecryptfs_aops = {
 556         .writepage = ecryptfs_writepage,
 557         .readpage = ecryptfs_readpage,
 558         .write_begin = ecryptfs_write_begin,
 559         .write_end = ecryptfs_write_end,
 560         .bmap = ecryptfs_bmap,
 561 };