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 "ecryptfs_kernel.h"
  36
  37 struct kmem_cache *ecryptfs_lower_page_cache;
  38
  39 /**
  40  * ecryptfs_get1page
  41  *
  42  * Get one page from cache or lower f/s, return error otherwise.
  43  *
  44  * Returns unlocked and up-to-date page (if ok), with increased
  45  * refcnt.
  46  */
  47 struct page *ecryptfs_get1page(struct file *file, loff_t index)
  48 {
  49         struct dentry *dentry;
  50         struct inode *inode;
  51         struct address_space *mapping;
  52
  53         dentry = file->f_path.dentry;
  54         inode = dentry->d_inode;
  55         mapping = inode->i_mapping;
  56         return read_mapping_page(mapping, index, (void *)file);
  57 }
  58
  59 /**
  60  * ecryptfs_fill_zeros
  61  * @file: The ecryptfs file
  62  * @new_length: The new length of the data in the underlying file;
  63  *              everything between the prior end of the file and the
  64  *              new end of the file will be filled with zero's.
  65  *              new_length must be greater than  current length
  66  *
  67  * Function for handling lseek-ing past the end of the file.
  68  *
  69  * This function does not support shrinking, only growing a file.
  70  *
  71  * Returns zero on success; non-zero otherwise.
  72  */
  73 int ecryptfs_fill_zeros(struct file *file, loff_t new_length)
  74 {
  75         int rc = 0;
  76         struct dentry *dentry = file->f_path.dentry;
  77         struct inode *inode = dentry->d_inode;
  78         pgoff_t old_end_page_index = 0;
  79         pgoff_t index = old_end_page_index;
  80         int old_end_pos_in_page = -1;
  81         pgoff_t new_end_page_index;
  82         int new_end_pos_in_page;
  83         loff_t cur_length = i_size_read(inode);
  84
  85         if (cur_length != 0) {
  86                 index = old_end_page_index =
  87                     ((cur_length - 1) >> PAGE_CACHE_SHIFT);
  88                 old_end_pos_in_page = ((cur_length - 1) & ~PAGE_CACHE_MASK);
  89         }
  90         new_end_page_index = ((new_length - 1) >> PAGE_CACHE_SHIFT);
  91         new_end_pos_in_page = ((new_length - 1) & ~PAGE_CACHE_MASK);
  92         ecryptfs_printk(KERN_DEBUG, "old_end_page_index = [0x%.16x]; "
  93                         "old_end_pos_in_page = [%d]; "
  94                         "new_end_page_index = [0x%.16x]; "
  95                         "new_end_pos_in_page = [%d]\n",
  96                         old_end_page_index, old_end_pos_in_page,
  97                         new_end_page_index, new_end_pos_in_page);
  98         if (old_end_page_index == new_end_page_index) {
  99                 /* Start and end are in the same page; we just need to
 100                  * set a portion of the existing page to zero's */
 101                 rc = ecryptfs_write_zeros(file, index,
 102                                           (old_end_pos_in_page + 1),
 103                                           (new_end_pos_in_page
 104                                            - old_end_pos_in_page));
 105                 if (rc)
 106                         ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros("
 107                                         "file=[%p], "
 108                                         "index=[0x%.16x], "
 109                                         "old_end_pos_in_page=[d], "
 110                                         "(PAGE_CACHE_SIZE - new_end_pos_in_page"
 111                                         "=[%d]"
 112                                         ")=[d]) returned [%d]\n", file, index,
 113                                         old_end_pos_in_page,
 114                                         new_end_pos_in_page,
 115                                         (PAGE_CACHE_SIZE - new_end_pos_in_page),
 116                                         rc);
 117                 goto out;
 118         }
 119         /* Fill the remainder of the previous last page with zeros */
 120         rc = ecryptfs_write_zeros(file, index, (old_end_pos_in_page + 1),
 121                          ((PAGE_CACHE_SIZE - 1) - old_end_pos_in_page));
 122         if (rc) {
 123                 ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros(file=[%p], "
 124                                 "index=[0x%.16x], old_end_pos_in_page=[d], "
 125                                 "(PAGE_CACHE_SIZE - old_end_pos_in_page)=[d]) "
 126                                 "returned [%d]\n", file, index,
 127                                 old_end_pos_in_page,
 128                                 (PAGE_CACHE_SIZE - old_end_pos_in_page), rc);
 129                 goto out;
 130         }
 131         index++;
 132         while (index < new_end_page_index) {
 133                 /* Fill all intermediate pages with zeros */
 134                 rc = ecryptfs_write_zeros(file, index, 0, PAGE_CACHE_SIZE);
 135                 if (rc) {
 136                         ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros("
 137                                         "file=[%p], "
 138                                         "index=[0x%.16x], "
 139                                         "old_end_pos_in_page=[d], "
 140                                         "(PAGE_CACHE_SIZE - new_end_pos_in_page"
 141                                         "=[%d]"
 142                                         ")=[d]) returned [%d]\n", file, index,
 143                                         old_end_pos_in_page,
 144                                         new_end_pos_in_page,
 145                                         (PAGE_CACHE_SIZE - new_end_pos_in_page),
 146                                         rc);
 147                         goto out;
 148                 }
 149                 index++;
 150         }
 151         /* Fill the portion at the beginning of the last new page with
 152          * zero's */
 153         rc = ecryptfs_write_zeros(file, index, 0, (new_end_pos_in_page + 1));
 154         if (rc) {
 155                 ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros(file="
 156                                 "[%p], index=[0x%.16x], 0, "
 157                                 "new_end_pos_in_page=[%d]"
 158                                 "returned [%d]\n", file, index,
 159                                 new_end_pos_in_page, rc);
 160                 goto out;
 161         }
 162 out:
 163         return rc;
 164 }
 165
 166 /**
 167  * ecryptfs_writepage
 168  * @page: Page that is locked before this call is made
 169  *
 170  * Returns zero on success; non-zero otherwise
 171  */
 172 static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
 173 {
 174         int rc;
 175
 176         rc = ecryptfs_encrypt_page(page);
 177         if (rc) {
 178                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
 179                                 "page (upper index [0x%.16x])\n", page->index);
 180                 ClearPageUptodate(page);
 181                 goto out;
 182         }
 183         SetPageUptodate(page);
 184         unlock_page(page);
 185 out:
 186         return rc;
 187 }
 188
 189 /**
 190  * Reads the data from the lower file file at index lower_page_index
 191  * and copies that data into page.
 192  *
 193  * @param page  Page to fill
 194  * @param lower_page_index Index of the page in the lower file to get
 195  */
 196 int ecryptfs_do_readpage(struct file *file, struct page *page,
 197                          pgoff_t lower_page_index)
 198 {
 199         int rc;
 200         struct dentry *dentry;
 201         struct file *lower_file;
 202         struct dentry *lower_dentry;
 203         struct inode *inode;
 204         struct inode *lower_inode;
 205         char *page_data;
 206         struct page *lower_page = NULL;
 207         char *lower_page_data;
 208         const struct address_space_operations *lower_a_ops;
 209
 210         dentry = file->f_path.dentry;
 211         lower_file = ecryptfs_file_to_lower(file);
 212         lower_dentry = ecryptfs_dentry_to_lower(dentry);
 213         inode = dentry->d_inode;
 214         lower_inode = ecryptfs_inode_to_lower(inode);
 215         lower_a_ops = lower_inode->i_mapping->a_ops;
 216         lower_page = read_cache_page(lower_inode->i_mapping, lower_page_index,
 217                                      (filler_t *)lower_a_ops->readpage,
 218                                      (void *)lower_file);
 219         if (IS_ERR(lower_page)) {
 220                 rc = PTR_ERR(lower_page);
 221                 lower_page = NULL;
 222                 ecryptfs_printk(KERN_ERR, "Error reading from page cache\n");
 223                 goto out;
 224         }
 225         page_data = kmap_atomic(page, KM_USER0);
 226         lower_page_data = kmap_atomic(lower_page, KM_USER1);
 227         memcpy(page_data, lower_page_data, PAGE_CACHE_SIZE);
 228         kunmap_atomic(lower_page_data, KM_USER1);
 229         kunmap_atomic(page_data, KM_USER0);
 230         flush_dcache_page(page);
 231         rc = 0;
 232 out:
 233         if (likely(lower_page))
 234                 page_cache_release(lower_page);
 235         if (rc == 0)
 236                 SetPageUptodate(page);
 237         else
 238                 ClearPageUptodate(page);
 239         return rc;
 240 }
 241 /**
 242  *   Header Extent:
 243  *     Octets 0-7:        Unencrypted file size (big-endian)
 244  *     Octets 8-15:       eCryptfs special marker
 245  *     Octets 16-19:      Flags
 246  *      Octet 16:         File format version number (between 0 and 255)
 247  *      Octets 17-18:     Reserved
 248  *      Octet 19:         Bit 1 (lsb): Reserved
 249  *                        Bit 2: Encrypted?
 250  *                        Bits 3-8: Reserved
 251  *     Octets 20-23:      Header extent size (big-endian)
 252  *     Octets 24-25:      Number of header extents at front of file
 253  *                        (big-endian)
 254  *     Octet  26:         Begin RFC 2440 authentication token packet set
 255  */
 256 static void set_header_info(char *page_virt,
 257                             struct ecryptfs_crypt_stat *crypt_stat)
 258 {
 259         size_t written;
 260         int save_num_header_extents_at_front =
 261                 crypt_stat->num_header_extents_at_front;
 262
 263         crypt_stat->num_header_extents_at_front = 1;
 264         ecryptfs_write_header_metadata(page_virt + 20, crypt_stat, &written);
 265         crypt_stat->num_header_extents_at_front =
 266                 save_num_header_extents_at_front;
 267 }
 268
 269 /**
 270  * ecryptfs_copy_up_encrypted_with_header
 271  * @page: Sort of a ``virtual'' representation of the encrypted lower
 272  *        file. The actual lower file does not have the metadata in
 273  *        the header. This is locked.
 274  * @crypt_stat: The eCryptfs inode's cryptographic context
 275  *
 276  * The ``view'' is the version of the file that userspace winds up
 277  * seeing, with the header information inserted.
 278  */
 279 static int
 280 ecryptfs_copy_up_encrypted_with_header(struct page *page,
 281                                        struct ecryptfs_crypt_stat *crypt_stat)
 282 {
 283         loff_t extent_num_in_page = 0;
 284         loff_t num_extents_per_page = (PAGE_CACHE_SIZE
 285                                        / crypt_stat->extent_size);
 286         int rc = 0;
 287
 288         while (extent_num_in_page < num_extents_per_page) {
 289                 loff_t view_extent_num = ((page->index * num_extents_per_page)
 290                                           + extent_num_in_page);
 291
 292                 if (view_extent_num < crypt_stat->num_header_extents_at_front) {
 293                         /* This is a header extent */
 294                         char *page_virt;
 295
 296                         page_virt = kmap_atomic(page, KM_USER0);
 297                         memset(page_virt, 0, PAGE_CACHE_SIZE);
 298                         /* TODO: Support more than one header extent */
 299                         if (view_extent_num == 0) {
 300                                 rc = ecryptfs_read_xattr_region(
 301                                         page_virt, page->mapping->host);
 302                                 set_header_info(page_virt, crypt_stat);
 303                         }
 304                         kunmap_atomic(page_virt, KM_USER0);
 305                         flush_dcache_page(page);
 306                         if (rc) {
 307                                 ClearPageUptodate(page);
 308                                 printk(KERN_ERR "%s: Error reading xattr "
 309                                        "region; rc = [%d]\n", __FUNCTION__, rc);
 310                                 goto out;
 311                         }
 312                         SetPageUptodate(page);
 313                 } else {
 314                         /* This is an encrypted data extent */
 315                         loff_t lower_offset =
 316                                 ((view_extent_num -
 317                                   crypt_stat->num_header_extents_at_front)
 318                                  * crypt_stat->extent_size);
 319
 320                         rc = ecryptfs_read_lower_page_segment(
 321                                 page, (lower_offset >> PAGE_CACHE_SHIFT),
 322                                 (lower_offset & ~PAGE_CACHE_MASK),
 323                                 crypt_stat->extent_size, page->mapping->host);
 324                         if (rc) {
 325                                 printk(KERN_ERR "%s: Error attempting to read "
 326                                        "extent at offset [%lld] in the lower "
 327                                        "file; rc = [%d]\n", __FUNCTION__,
 328                                        lower_offset, rc);
 329                                 goto out;
 330                         }
 331                 }
 332                 extent_num_in_page++;
 333         }
 334 out:
 335         return rc;
 336 }
 337
 338 /**
 339  * ecryptfs_readpage
 340  * @file: An eCryptfs file
 341  * @page: Page from eCryptfs inode mapping into which to stick the read data
 342  *
 343  * Read in a page, decrypting if necessary.
 344  *
 345  * Returns zero on success; non-zero on error.
 346  */
 347 static int ecryptfs_readpage(struct file *file, struct page *page)
 348 {
 349         struct ecryptfs_crypt_stat *crypt_stat =
 350                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 351         int rc = 0;
 352
 353         if (!crypt_stat
 354             || !(crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 355             || (crypt_stat->flags & ECRYPTFS_NEW_FILE)) {
 356                 ecryptfs_printk(KERN_DEBUG,
 357                                 "Passing through unencrypted page\n");
 358                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 359                                                       PAGE_CACHE_SIZE,
 360                                                       page->mapping->host);
 361         } else if (crypt_stat->flags & ECRYPTFS_VIEW_AS_ENCRYPTED) {
 362                 if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR) {
 363                         rc = ecryptfs_copy_up_encrypted_with_header(page,
 364                                                                     crypt_stat);
 365                         if (rc) {
 366                                 printk(KERN_ERR "%s: Error attempting to copy "
 367                                        "the encrypted content from the lower "
 368                                        "file whilst inserting the metadata "
 369                                        "from the xattr into the header; rc = "
 370                                        "[%d]\n", __FUNCTION__, rc);
 371                                 goto out;
 372                         }
 373
 374                 } else {
 375                         rc = ecryptfs_read_lower_page_segment(
 376                                 page, page->index, 0, PAGE_CACHE_SIZE,
 377                                 page->mapping->host);
 378                         if (rc) {
 379                                 printk(KERN_ERR "Error reading page; rc = "
 380                                        "[%d]\n", rc);
 381                                 goto out;
 382                         }
 383                 }
 384         } else {
 385                 rc = ecryptfs_decrypt_page(page);
 386                 if (rc) {
 387                         ecryptfs_printk(KERN_ERR, "Error decrypting page; "
 388                                         "rc = [%d]\n", rc);
 389                         goto out;
 390                 }
 391         }
 392 out:
 393         ecryptfs_printk(KERN_DEBUG, "Unlocking page with index = [0x%.16x]\n",
 394                         page->index);
 395         unlock_page(page);
 396         return rc;
 397 }
 398
 399 /**
 400  * Called with lower inode mutex held.
 401  */
 402 static int fill_zeros_to_end_of_page(struct page *page, unsigned int to)
 403 {
 404         struct inode *inode = page->mapping->host;
 405         int end_byte_in_page;
 406
 407         if ((i_size_read(inode) / PAGE_CACHE_SIZE) != page->index)
 408                 goto out;
 409         end_byte_in_page = i_size_read(inode) % PAGE_CACHE_SIZE;
 410         if (to > end_byte_in_page)
 411                 end_byte_in_page = to;
 412         zero_user_page(page, end_byte_in_page,
 413                 PAGE_CACHE_SIZE - end_byte_in_page, KM_USER0);
 414 out:
 415         return 0;
 416 }
 417
 418 /**
 419  * eCryptfs does not currently support holes. When writing after a
 420  * seek past the end of the file, eCryptfs fills in 0's through to the
 421  * current location. The code to fill in the 0's to all the
 422  * intermediate pages calls ecryptfs_prepare_write_no_truncate().
 423  */
 424 static int
 425 ecryptfs_prepare_write_no_truncate(struct file *file, struct page *page,
 426                                    unsigned from, unsigned to)
 427 {
 428         int rc = 0;
 429
 430         if (from == 0 && to == PAGE_CACHE_SIZE)
 431                 goto out;       /* If we are writing a full page, it will be
 432                                    up to date. */
 433         if (!PageUptodate(page))
 434                 rc = ecryptfs_do_readpage(file, page, page->index);
 435 out:
 436         return rc;
 437 }
 438
 439 static int ecryptfs_prepare_write(struct file *file, struct page *page,
 440                                   unsigned from, unsigned to)
 441 {
 442         int rc = 0;
 443
 444         if (from == 0 && to == PAGE_CACHE_SIZE)
 445                 goto out;       /* If we are writing a full page, it will be
 446                                    up to date. */
 447         if (!PageUptodate(page))
 448                 rc = ecryptfs_read_lower_page_segment(page, page->index, 0,
 449                                                       PAGE_CACHE_SIZE,
 450                                                       page->mapping->host);
 451         if (page->index != 0) {
 452                 loff_t end_of_prev_pg_pos =
 453                         (((loff_t)page->index << PAGE_CACHE_SHIFT) - 1);
 454
 455                 if (end_of_prev_pg_pos > i_size_read(page->mapping->host)) {
 456                         rc = ecryptfs_truncate(file->f_path.dentry,
 457                                                end_of_prev_pg_pos);
 458                         if (rc) {
 459                                 printk(KERN_ERR "Error on attempt to "
 460                                        "truncate to (higher) offset [%lld];"
 461                                        " rc = [%d]\n", end_of_prev_pg_pos, rc);
 462                                 goto out;
 463                         }
 464                 }
 465                 if (end_of_prev_pg_pos + 1 > i_size_read(page->mapping->host))
 466                         zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
 467         }
 468 out:
 469         return rc;
 470 }
 471
 472 int ecryptfs_writepage_and_release_lower_page(struct page *lower_page,
 473                                               struct inode *lower_inode,
 474                                               struct writeback_control *wbc)
 475 {
 476         int rc = 0;
 477
 478         rc = lower_inode->i_mapping->a_ops->writepage(lower_page, wbc);
 479         if (rc) {
 480                 ecryptfs_printk(KERN_ERR, "Error calling lower writepage(); "
 481                                 "rc = [%d]\n", rc);
 482                 goto out;
 483         }
 484         lower_inode->i_mtime = lower_inode->i_ctime = CURRENT_TIME;
 485         page_cache_release(lower_page);
 486 out:
 487         return rc;
 488 }
 489
 490 static void ecryptfs_release_lower_page(struct page *lower_page)
 491 {
 492         unlock_page(lower_page);
 493         page_cache_release(lower_page);
 494 }
 495
 496 /**
 497  * ecryptfs_write_inode_size_to_header
 498  *
 499  * Writes the lower file size to the first 8 bytes of the header.
 500  *
 501  * Returns zero on success; non-zero on error.
 502  */
 503 static int ecryptfs_write_inode_size_to_header(struct inode *ecryptfs_inode)
 504 {
 505         u64 file_size;
 506         char *file_size_virt;
 507         int rc;
 508
 509         file_size_virt = kmalloc(sizeof(u64), GFP_KERNEL);
 510         if (!file_size_virt) {
 511                 rc = -ENOMEM;
 512                 goto out;
 513         }
 514         file_size = (u64)i_size_read(ecryptfs_inode);
 515         file_size = cpu_to_be64(file_size);
 516         memcpy(file_size_virt, &file_size, sizeof(u64));
 517         rc = ecryptfs_write_lower(ecryptfs_inode, file_size_virt, 0,
 518                                   sizeof(u64));
 519         kfree(file_size_virt);
 520         if (rc)
 521                 printk(KERN_ERR "%s: Error writing file size to header; "
 522                        "rc = [%d]\n", __FUNCTION__, rc);
 523 out:
 524         return rc;
 525 }
 526
 527 struct kmem_cache *ecryptfs_xattr_cache;
 528
 529 static int ecryptfs_write_inode_size_to_xattr(struct inode *ecryptfs_inode)
 530 {
 531         ssize_t size;
 532         void *xattr_virt;
 533         struct dentry *lower_dentry =
 534                 ecryptfs_inode_to_private(ecryptfs_inode)->lower_file->f_dentry;
 535         struct inode *lower_inode = lower_dentry->d_inode;
 536         u64 file_size;
 537         int rc;
 538
 539         if (!lower_inode->i_op->getxattr || !lower_inode->i_op->setxattr) {
 540                 printk(KERN_WARNING
 541                        "No support for setting xattr in lower filesystem\n");
 542                 rc = -ENOSYS;
 543                 goto out;
 544         }
 545         xattr_virt = kmem_cache_alloc(ecryptfs_xattr_cache, GFP_KERNEL);
 546         if (!xattr_virt) {
 547                 printk(KERN_ERR "Out of memory whilst attempting to write "
 548                        "inode size to xattr\n");
 549                 rc = -ENOMEM;
 550                 goto out;
 551         }
 552         mutex_lock(&lower_inode->i_mutex);
 553         size = lower_inode->i_op->getxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 554                                            xattr_virt, PAGE_CACHE_SIZE);
 555         if (size < 0)
 556                 size = 8;
 557         file_size = (u64)i_size_read(ecryptfs_inode);
 558         file_size = cpu_to_be64(file_size);
 559         memcpy(xattr_virt, &file_size, sizeof(u64));
 560         rc = lower_inode->i_op->setxattr(lower_dentry, ECRYPTFS_XATTR_NAME,
 561                                          xattr_virt, size, 0);
 562         mutex_unlock(&lower_inode->i_mutex);
 563         if (rc)
 564                 printk(KERN_ERR "Error whilst attempting to write inode size "
 565                        "to lower file xattr; rc = [%d]\n", rc);
 566         kmem_cache_free(ecryptfs_xattr_cache, xattr_virt);
 567 out:
 568         return rc;
 569 }
 570
 571 int ecryptfs_write_inode_size_to_metadata(struct inode *ecryptfs_inode)
 572 {
 573         struct ecryptfs_crypt_stat *crypt_stat;
 574
 575         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 576         if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
 577                 return ecryptfs_write_inode_size_to_xattr(ecryptfs_inode);
 578         else
 579                 return ecryptfs_write_inode_size_to_header(ecryptfs_inode);
 580 }
 581
 582 int ecryptfs_get_lower_page(struct page **lower_page, struct inode *lower_inode,
 583                             struct file *lower_file,
 584                             unsigned long lower_page_index, int byte_offset,
 585                             int region_bytes)
 586 {
 587         int rc = 0;
 588
 589         *lower_page = grab_cache_page(lower_inode->i_mapping, lower_page_index);
 590         if (!(*lower_page)) {
 591                 rc = -EINVAL;
 592                 ecryptfs_printk(KERN_ERR, "Error attempting to grab "
 593                                 "lower page with index [0x%.16x]\n",
 594                                 lower_page_index);
 595                 goto out;
 596         }
 597         rc = lower_inode->i_mapping->a_ops->prepare_write(lower_file,
 598                                                           (*lower_page),
 599                                                           byte_offset,
 600                                                           region_bytes);
 601         if (rc) {
 602                 ecryptfs_printk(KERN_ERR, "prepare_write for "
 603                         "lower_page_index = [0x%.16x] failed; rc = "
 604                         "[%d]\n", lower_page_index, rc);
 605                 ecryptfs_release_lower_page(*lower_page);
 606                 (*lower_page) = NULL;
 607         }
 608 out:
 609         return rc;
 610 }
 611
 612 /**
 613  * ecryptfs_commit_lower_page
 614  *
 615  * Returns zero on success; non-zero on error
 616  */
 617 int
 618 ecryptfs_commit_lower_page(struct page *lower_page, struct inode *lower_inode,
 619                            struct file *lower_file, int byte_offset,
 620                            int region_size)
 621 {
 622         int rc = 0;
 623
 624         rc = lower_inode->i_mapping->a_ops->commit_write(
 625                 lower_file, lower_page, byte_offset, region_size);
 626         if (rc < 0) {
 627                 ecryptfs_printk(KERN_ERR,
 628                                 "Error committing write; rc = [%d]\n", rc);
 629         } else
 630                 rc = 0;
 631         ecryptfs_release_lower_page(lower_page);
 632         return rc;
 633 }
 634
 635 /**
 636  * ecryptfs_copy_page_to_lower
 637  *
 638  * Used for plaintext pass-through; no page index interpolation
 639  * required.
 640  */
 641 int ecryptfs_copy_page_to_lower(struct page *page, struct inode *lower_inode,
 642                                 struct file *lower_file)
 643 {
 644         int rc = 0;
 645         struct page *lower_page;
 646
 647         rc = ecryptfs_get_lower_page(&lower_page, lower_inode, lower_file,
 648                                      page->index, 0, PAGE_CACHE_SIZE);
 649         if (rc) {
 650                 ecryptfs_printk(KERN_ERR, "Error attempting to get page "
 651                                 "at index [0x%.16x]\n", page->index);
 652                 goto out;
 653         }
 654         /* TODO: aops */
 655         memcpy((char *)page_address(lower_page), page_address(page),
 656                PAGE_CACHE_SIZE);
 657         rc = ecryptfs_commit_lower_page(lower_page, lower_inode, lower_file,
 658                                         0, PAGE_CACHE_SIZE);
 659         if (rc)
 660                 ecryptfs_printk(KERN_ERR, "Error attempting to commit page "
 661                                 "at index [0x%.16x]\n", page->index);
 662 out:
 663         return rc;
 664 }
 665
 666 /**
 667  * ecryptfs_commit_write
 668  * @file: The eCryptfs file object
 669  * @page: The eCryptfs page
 670  * @from: Ignored (we rotate the page IV on each write)
 671  * @to: Ignored
 672  *
 673  * This is where we encrypt the data and pass the encrypted data to
 674  * the lower filesystem.  In OpenPGP-compatible mode, we operate on
 675  * entire underlying packets.
 676  */
 677 static int ecryptfs_commit_write(struct file *file, struct page *page,
 678                                  unsigned from, unsigned to)
 679 {
 680         loff_t pos;
 681         struct inode *ecryptfs_inode = page->mapping->host;
 682         struct ecryptfs_crypt_stat *crypt_stat =
 683                 &ecryptfs_inode_to_private(file->f_path.dentry->d_inode)->crypt_stat;
 684         int rc;
 685
 686         if (crypt_stat->flags & ECRYPTFS_NEW_FILE) {
 687                 ecryptfs_printk(KERN_DEBUG, "ECRYPTFS_NEW_FILE flag set in "
 688                         "crypt_stat at memory location [%p]\n", crypt_stat);
 689                 crypt_stat->flags &= ~(ECRYPTFS_NEW_FILE);
 690         } else
 691                 ecryptfs_printk(KERN_DEBUG, "Not a new file\n");
 692         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
 693                         "(page w/ index = [0x%.16x], to = [%d])\n", page->index,
 694                         to);
 695         /* Fills in zeros if 'to' goes beyond inode size */
 696         rc = fill_zeros_to_end_of_page(page, to);
 697         if (rc) {
 698                 ecryptfs_printk(KERN_WARNING, "Error attempting to fill "
 699                                 "zeros in page with index = [0x%.16x]\n",
 700                                 page->index);
 701                 goto out;
 702         }
 703         rc = ecryptfs_encrypt_page(page);
 704         if (rc) {
 705                 ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
 706                                 "index [0x%.16x])\n", page->index);
 707                 goto out;
 708         }
 709         pos = (page->index << PAGE_CACHE_SHIFT) + to;
 710         if (pos > i_size_read(ecryptfs_inode)) {
 711                 i_size_write(ecryptfs_inode, pos);
 712                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
 713                                 "[0x%.16x]\n", i_size_read(ecryptfs_inode));
 714         }
 715         rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
 716         if (rc)
 717                 printk(KERN_ERR "Error writing inode size to metadata; "
 718                        "rc = [%d]\n", rc);
 719 out:
 720         return rc;
 721 }
 722
 723 /**
 724  * ecryptfs_write_zeros
 725  * @file: The ecryptfs file
 726  * @index: The index in which we are writing
 727  * @start: The position after the last block of data
 728  * @num_zeros: The number of zeros to write
 729  *
 730  * Write a specified number of zero's to a page.
 731  *
 732  * (start + num_zeros) must be less than or equal to PAGE_CACHE_SIZE
 733  */
 734 int
 735 ecryptfs_write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
 736 {
 737         int rc = 0;
 738         struct page *tmp_page;
 739
 740         tmp_page = ecryptfs_get1page(file, index);
 741         if (IS_ERR(tmp_page)) {
 742                 ecryptfs_printk(KERN_ERR, "Error getting page at index "
 743                                 "[0x%.16x]\n", index);
 744                 rc = PTR_ERR(tmp_page);
 745                 goto out;
 746         }
 747         rc = ecryptfs_prepare_write_no_truncate(file, tmp_page, start,
 748                                                 (start + num_zeros));
 749         if (rc) {
 750                 ecryptfs_printk(KERN_ERR, "Error preparing to write zero's "
 751                                 "to page at index [0x%.16x]\n",
 752                                 index);
 753                 page_cache_release(tmp_page);
 754                 goto out;
 755         }
 756         zero_user_page(tmp_page, start, num_zeros, KM_USER0);
 757         rc = ecryptfs_commit_write(file, tmp_page, start, start + num_zeros);
 758         if (rc < 0) {
 759                 ecryptfs_printk(KERN_ERR, "Error attempting to write zero's "
 760                                 "to remainder of page at index [0x%.16x]\n",
 761                                 index);
 762                 page_cache_release(tmp_page);
 763                 goto out;
 764         }
 765         rc = 0;
 766         page_cache_release(tmp_page);
 767 out:
 768         return rc;
 769 }
 770
 771 static sector_t ecryptfs_bmap(struct address_space *mapping, sector_t block)
 772 {
 773         int rc = 0;
 774         struct inode *inode;
 775         struct inode *lower_inode;
 776
 777         inode = (struct inode *)mapping->host;
 778         lower_inode = ecryptfs_inode_to_lower(inode);
 779         if (lower_inode->i_mapping->a_ops->bmap)
 780                 rc = lower_inode->i_mapping->a_ops->bmap(lower_inode->i_mapping,
 781                                                          block);
 782         return rc;
 783 }
 784
 785 struct address_space_operations ecryptfs_aops = {
 786         .writepage = ecryptfs_writepage,
 787         .readpage = ecryptfs_readpage,
 788         .prepare_write = ecryptfs_prepare_write,
 789         .commit_write = ecryptfs_commit_write,
 790         .bmap = ecryptfs_bmap,
 791 };