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 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
  62 {
  63         int rc;
  64
  65         /*
  66          * Refuse to write the page out if we are called from reclaim context
  67          * since our writepage() path may potentially allocate memory when
  68          * calling into the lower fs vfs_write() which may in turn invoke
  69          * us again.
  70          */
  71         if (current->flags & PF_MEMALLOC) {
  72                 redirty_page_for_writepage(wbc, page);
  73                 rc = 0;
  74                 goto out;
  75         }
  76
  77         rc = ecryptfs_encrypt_page(page);
  78         if (rc) {
  79                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
  80                                 "page (upper index [0x%.16lx])\n", page->index);
  81                 ClearPageUptodate(page);
  82                 goto out;
  83         }
  84         SetPageUptodate(page);
  85 out:
  86         unlock_page(page);
  87         return rc;
  88 }
  89
  90 static void strip_xattr_flag(char *page_virt,
  91                              struct ecryptfs_crypt_stat *crypt_stat)
  92 {
  93         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
  94                 size_t written;
  95
  96                 crypt_stat->flags &= ~ECRYPTFS_METADATA_IN_XATTR;
  97                 ecryptfs_write_crypt_stat_flags(page_virt, crypt_stat,
  98                                                 &written);
  99                 crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
 100         }
 101 }
 102
 103 /**
 104  *   Header Extent:
 105  *     Octets 0-7:        Unencrypted file size (big-endian)
 106  *     Octets 8-15:       eCryptfs special marker
 107  *     Octets 16-19:      Flags
 108  *      Octet 16:         File format version number (between 0 and 255)
 109  *      Octets 17-18:     Reserved
 110  *      Octet 19:         Bit 1 (lsb): Reserved
 111  *                        Bit 2: Encrypted?
 112  *                        Bits 3-8: Reserved
 113  *     Octets 20-23:      Header extent size (big-endian)
 114  *     Octets 24-25:      Number of header extents at front of file
 115  *                        (big-endian)
 116  *     Octet  26:         Begin RFC 2440 authentication token packet set
 117  */
 118
 119 /**
 120  * ecryptfs_copy_up_encrypted_with_header
 121  * @page: Sort of a ``virtual'' representation of the encrypted lower
 122  *        file. The actual lower file does not have the metadata in
 123  *        the header. This is locked.
 124  * @crypt_stat: The eCryptfs inode's cryptographic context
 125  *
 126  * The ``view'' is the version of the file that userspace winds up
 127  * seeing, with the header information inserted.
 128  */
 129 static int
 130 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 131                                        struct ecryptfs_crypt_stat *crypt_stat)
 132 {
 133         loff_t extent_num_in_page = 0;
 134         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 135                                        / crypt_stat->extent_size);
 136         int rc = 0;
 137
 138         while (extent_num_in_page < num_extents_per_page) {
 139                 loff_t view_extent_num = ((((loff_t)page->index)
 140                                            * num_extents_per_page)
 141                                           + extent_num_in_page);
 142                 size_t num_header_extents_at_front =
 143                         (crypt_stat->metadata_size / crypt_stat->extent_size);
 144
 145                 if (view_extent_num < num_header_extents_at_front) {
 146                         /* This is a header extent */
 147                         char *page_virt;
 148
 149                         page_virt = kmap_atomic(page, KM_USER0);
 150                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 151                         /* TODO: Support more than one header extent */
 152                         if (view_extent_num == 0) {
 153                                 size_t written;
 154
 155                                 rc = ecryptfs_read_xattr_region(
 156                                         page_virt, page->mapping->host);
 157                                 strip_xattr_flag(page_virt + 16, crypt_stat);
 158                                 ecryptfs_write_header_metadata(page_virt + 20,
 159                                                                crypt_stat,
 160                                                                &written);
 161                         }
 162                         kunmap_atomic(page_virt, KM_USER0);
 163                         flush_dcache_page(page);
 164                         if (rc) {
 165                                 printk(KERN_ERR "%s: Error reading xattr "
 166                                        "region; rc = [%d]\n", __func__, rc);
 167                                 goto out;
 168                         }
 169                 } else {
 170                         /* This is an encrypted data extent */
 171                         loff_t lower_offset =
 172                                 ((view_extent_num * crypt_stat->extent_size)
 173                                  - crypt_stat->metadata_size);
 174
 175                         rc = ecryptfs_read_lower_page_segment(
 176                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 177                                 (lower_offset & ~PAGE_CACHE_MASK),
 178                                 crypt_stat->extent_size, page->mapping->host);
 179                         if (rc) {
 180                                 printk(KERN_ERR "%s: Error attempting to read "
 181                                        "extent at offset [%lld] in the lower "
 182                                        "file; rc = [%d]\n", __func__,
 183                                        lower_offset, rc);
 184                                 goto out;
 185                         }
 186                 }
 187                 extent_num_in_page++;
 188         }
 189 out:
 190         return rc;
 191 }
 192
 193 /**
 194  * ecryptfs_readpage
 195  * @file: An eCryptfs file
 196  * @page: Page from eCryptfs inode mapping into which to stick the read data
 197  *
 198  * Read in a page, decrypting if necessary.
 199  *
 200  * Returns zero on success; non-zero on error.
 201  */
 202 static int ecryptfs_readpage(struct file *file, struct page *page)
 203 {
 204         struct ecryptfs_crypt_stat *crypt_stat =
 205                 &ecryptfs_inode_to_private(page->mapping->host)->crypt_stat;
 206         int rc = 0;
 207
 208         if (!crypt_stat || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 209                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 210                                                       PAGE_CACHE_SIZE,
 211                                                       page->mapping->host);
 212         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 213                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 214                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 215                                                                     crypt_stat);
 216                         if (rc) {
 217                                 printk(KERN_ERR "%s: Error attempting to copy "
 218                                        "the encrypted content from the lower "
 219                                        "file whilst inserting the metadata "
 220                                        "from the xattr into the header; rc = "
 221                                        "[%d]\n", __func__, rc);
 222                                 goto out;
 223                         }
 224
 225                 } else {
 226                         rc = ecryptfs_read_lower_page_segment(
 227                                 page, page->index, 0, PAGE_CACHE_SIZE,
 228                                 page->mapping->host);
 229                         if (rc) {
 230                                 printk(KERN_ERR "Error reading page; rc = "
 231                                        "[%d]\n", rc);
 232                                 goto out;
 233                         }
 234                 }
 235         } else {
 236                 rc = ecryptfs_decrypt_page(page);
 237                 if (rc) {
 238                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 239                                         "rc = [%d]\n", rc);
 240                         goto out;
 241                 }
 242         }
 243 out:
 244         if (rc)
 245                 ClearPageUptodate(page);
 246         else
 247                 SetPageUptodate(page);
 248         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16lx]\n",
 249                         page->index);
 250         unlock_page(page);
 251         return rc;
 252 }
 253
 254 /**
 255  * Called with lower inode mutex held.
 256  */
 257 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 258 {
 259         struct inode *inode = page->mapping->host;
 260         int end_byte_in_page;
 261
 262         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 263                 goto out;
 264         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 265         if (to > end_byte_in_page)
 266                 end_byte_in_page = to;
 267         zero_user_segment(page, end_byte_in_page, PAGE_CACHE_SIZE);
 268 out:
 269         return 0;
 270 }
 271
 272 /**
 273  * ecryptfs_write_begin
 274  * @file: The eCryptfs file
 275  * @mapping: The eCryptfs object
 276  * @pos: The file offset at which to start writing
 277  * @len: Length of the write
 278  * @flags: Various flags
 279  * @pagep: Pointer to return the page
 280  * @fsdata: Pointer to return fs data (unused)
 281  *
 282  * This function must zero any hole we create
 283  *
 284  * Returns zero on success; non-zero otherwise
 285  */
 286 static int ecryptfs_write_begin(struct file *file,
 287                         struct address_space *mapping,
 288                         loff_t pos, unsigned len, unsigned flags,
 289                         struct page **pagep, void **fsdata)
 290 {
 291         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 292         struct page *page;
 293         loff_t prev_page_end_size;
 294         int rc = 0;
 295
 296         page = grab_cache_page_write_begin(mapping, index, flags);
 297         if (!page)
 298                 return -ENOMEM;
 299         *pagep = page;
 300
 301         prev_page_end_size = ((loff_t)index << PAGE_CACHE_SHIFT);
 302         if (!PageUptodate(page)) {
 303                 struct ecryptfs_crypt_stat *crypt_stat =
 304                         &ecryptfs_inode_to_private(mapping->host)->crypt_stat;
 305
 306                 if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 307                         rc = ecryptfs_read_lower_page_segment(
 308                                 page, index, 0, PAGE_CACHE_SIZE, mapping->host);
 309                         if (rc) {
 310                                 printk(KERN_ERR "%s: Error attemping to read "
 311                                        "lower page segment; rc = [%d]\n",
 312                                        __func__, rc);
 313                                 ClearPageUptodate(page);
 314                                 goto out;
 315                         } else
 316                                 SetPageUptodate(page);
 317                 } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 318                         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 319                                 rc = ecryptfs_copy_up_encrypted_with_header(
 320                                         page, crypt_stat);
 321                                 if (rc) {
 322                                         printk(KERN_ERR "%s: Error attempting "
 323                                                "to copy the encrypted content "
 324                                                "from the lower file whilst "
 325                                                "inserting the metadata from "
 326                                                "the xattr into the header; rc "
 327                                                "= [%d]\n", __func__, rc);
 328                                         ClearPageUptodate(page);
 329                                         goto out;
 330                                 }
 331                                 SetPageUptodate(page);
 332                         } else {
 333                                 rc = ecryptfs_read_lower_page_segment(
 334                                         page, index, 0, PAGE_CACHE_SIZE,
 335                                         mapping->host);
 336                                 if (rc) {
 337                                         printk(KERN_ERR "%s: Error reading "
 338                                                "page; rc = [%d]\n",
 339                                                __func__, rc);
 340                                         ClearPageUptodate(page);
 341                                         goto out;
 342                                 }
 343                                 SetPageUptodate(page);
 344                         }
 345                 } else {
 346                         if (prev_page_end_size
 347                             >= i_size_read(page->mapping->host)) {
 348                                 zero_user(page, 0, PAGE_CACHE_SIZE);
 349                         } else {
 350                                 rc = ecryptfs_decrypt_page(page);
 351                                 if (rc) {
 352                                         printk(KERN_ERR "%s: Error decrypting "
 353                                                "page at index [%ld]; "
 354                                                "rc = [%d]\n",
 355                                                __func__, page->index, rc);
 356                                         ClearPageUptodate(page);
 357                                         goto out;
 358                                 }
 359                         }
 360                         SetPageUptodate(page);
 361                 }
 362         }
 363         /* If creating a page or more of holes, zero them out via truncate.
 364          * Note, this will increase i_size. */
 365         if (index != 0) {
 366                 if (prev_page_end_size > i_size_read(page->mapping->host)) {
 367                         rc = ecryptfs_truncate(file->f_path.dentry,
 368                                                prev_page_end_size);
 369                         if (rc) {
 370                                 printk(KERN_ERR "%s: Error on attempt to "
 371                                        "truncate to (higher) offset [%lld];"
 372                                        " rc = [%d]\n", __func__,
 373                                        prev_page_end_size, rc);
 374                                 goto out;
 375                         }
 376                 }
 377         }
 378         /* Writing to a new page, and creating a small hole from start
 379          * of page?  Zero it out. */
 380         if ((i_size_read(mapping->host) == prev_page_end_size)
 381             && (pos != 0))
 382                 zero_user(page, 0, PAGE_CACHE_SIZE);
 383 out:
 384         return rc;
 385 }
 386
 387 /**
 388  * ecryptfs_write_inode_size_to_header
 389  *
 390  * Writes the lower file size to the first 8 bytes of the header.
 391  *
 392  * Returns zero on success; non-zero on error.
 393  */
 394 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 395 {
 396         char *file_size_virt;
 397         int rc;
 398
 399         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 400         if (!file_size_virt) {
 401                 rc = -ENOMEM;
 402                 goto out;
 403         }
 404         put_unaligned_be64(i_size_read(ecryptfs_inode), file_size_virt);
 405         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 406                                   sizeof(u64));
 407         kfree(file_size_virt);
 408         if (rc < 0)
 409                 printk(KERN_ERR "%s: Error writing file size to header; "
 410                        "rc = [%d]\n", __func__, rc);
 411         else
 412                 rc = 0;
 413 out:
 414         return rc;
 415 }
 416
 417 struct kmem_cache *ecryptfs_xattr_cache;
 418
 419 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 420 {
 421         ssize_t size;
 422         void *xattr_virt;
 423         struct dentry *lower_dentry =
 424                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
 425         struct inode *lower_inode = lower_dentry->d_inode;
 426         int rc;
 427
 428         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 429                 printk(KERN_WARNING
 430                        "No support for setting xattr in lower filesystem\n");
 431                 rc = -ENOSYS;
 432                 goto out;
 433         }
 434         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 435         if (!xattr_virt) {
 436                 printk(KERN_ERR "Out of memory whilst attempting to write "
 437                        "inode size to xattr\n");
 438                 rc = -ENOMEM;
 439                 goto out;
 440         }
 441         mutex_lock(&lower_inode->i_mutex);
 442         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 443                                            xattr_virt, PAGE_CACHE_SIZE);
 444         if (size < 0)
 445                 size = 8;
 446         put_unaligned_be64(i_size_read(ecryptfs_inode), xattr_virt);
 447         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 448                                          xattr_virt, size, 0);
 449         mutex_unlock(&lower_inode->i_mutex);
 450         if (rc)
 451                 printk(KERN_ERR "Error whilst attempting to write inode size "
 452                        "to lower file xattr; rc = [%d]\n", rc);
 453         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 454 out:
 455         return rc;
 456 }
 457
 458 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 459 {
 460         struct ecryptfs_crypt_stat *crypt_stat;
 461
 462         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 463         BUG_ON(!(crypt_stat->flags & ECRYPTFS_ENCRYPTED));
 464         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 465                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 466         else
 467                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 468 }
 469
 470 /**
 471  * ecryptfs_write_end
 472  * @file: The eCryptfs file object
 473  * @mapping: The eCryptfs object
 474  * @pos: The file position
 475  * @len: The length of the data (unused)
 476  * @copied: The amount of data copied
 477  * @page: The eCryptfs page
 478  * @fsdata: The fsdata (unused)
 479  *
 480  * This is where we encrypt the data and pass the encrypted data to
 481  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 482  * entire underlying packets.
 483  */
 484 static int ecryptfs_write_end(struct file *file,
 485                         struct address_space *mapping,
 486                         loff_t pos, unsigned len, unsigned copied,
 487                         struct page *page, void *fsdata)
 488 {
 489         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
 490         unsigned from = pos & (PAGE_CACHE_SIZE - 1);
 491         unsigned to = from + copied;
 492         struct inode *ecryptfs_inode = mapping->host;
 493         struct ecryptfs_crypt_stat *crypt_stat =
 494                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 495         int rc;
 496         int need_unlock_page = 1;
 497
 498         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 499                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
 500         if (!(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
 501                 rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, page, 0,
 502                                                        to);
 503                 if (!rc) {
 504                         rc = copied;
 505                         fsstack_copy_inode_size(ecryptfs_inode,
 506                                 ecryptfs_inode_to_lower(ecryptfs_inode));
 507                 }
 508                 goto out;
 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         set_page_dirty(page);
 518         unlock_page(page);
 519         need_unlock_page = 0;
 520         if (pos + copied > i_size_read(ecryptfs_inode)) {
 521                 i_size_write(ecryptfs_inode, pos + copied);
 522                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 523                         "[0x%.16llx]\n",
 524                         (unsigned long long)i_size_read(ecryptfs_inode));
 525                 balance_dirty_pages_ratelimited(mapping);
 526                 rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 527                 if (rc) {
 528                         printk(KERN_ERR "Error writing inode size to metadata; "
 529                                "rc = [%d]\n", rc);
 530                         goto out;
 531                 }
 532         }
 533         rc = copied;
 534 out:
 535         if (need_unlock_page)
 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 };