fs/ecryptfs/read_write.c

   1 /**
   2  * eCryptfs: Linux filesystem encryption layer
   3  *
   4  * Copyright (C) 2007 International Business Machines Corp.
   5  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation; either version 2 of the
  10  * License, or (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20  * 02111-1307, USA.
  21  */
  22
  23 #include <linux/fs.h>
  24 #include <linux/pagemap.h>
  25 #include "ecryptfs_kernel.h"
  26
  27 /**
  28  * ecryptfs_write_lower
  29  * @ecryptfs_inode: The eCryptfs inode
  30  * @data: Data to write
  31  * @offset: Byte offset in the lower file to which to write the data
  32  * @size: Number of bytes from @data to write at @offset in the lower
  33  *        file
  34  *
  35  * Write data to the lower file.
  36  *
  37  * Returns zero on success; non-zero on error
  38  */
  39 int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data,
  40                          loff_t offset, size_t size)
  41 {
  42         struct ecryptfs_inode_info *inode_info;
  43         ssize_t octets_written;
  44         mm_segment_t fs_save;
  45         int rc = 0;
  46
  47         inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
  48         mutex_lock(&inode_info->lower_file_mutex);
  49         BUG_ON(!inode_info->lower_file);
  50         inode_info->lower_file->f_pos = offset;
  51         fs_save = get_fs();
  52         set_fs(get_ds());
  53         octets_written = vfs_write(inode_info->lower_file, data, size,
  54                                    &inode_info->lower_file->f_pos);
  55         set_fs(fs_save);
  56         if (octets_written < 0) {
  57                 printk(KERN_ERR "%s: octets_written = [%td]; "
  58                        "expected [%td]\n", __FUNCTION__, octets_written, size);
  59                 rc = -EINVAL;
  60         }
  61         mutex_unlock(&inode_info->lower_file_mutex);
  62         mark_inode_dirty_sync(ecryptfs_inode);
  63         return rc;
  64 }
  65
  66 /**
  67  * ecryptfs_write_lower_page_segment
  68  * @ecryptfs_inode: The eCryptfs inode
  69  * @page_for_lower: The page containing the data to be written to the
  70  *                  lower file
  71  * @offset_in_page: The offset in the @page_for_lower from which to
  72  *                  start writing the data
  73  * @size: The amount of data from @page_for_lower to write to the
  74  *        lower file
  75  *
  76  * Determines the byte offset in the file for the given page and
  77  * offset within the page, maps the page, and makes the call to write
  78  * the contents of @page_for_lower to the lower inode.
  79  *
  80  * Returns zero on success; non-zero otherwise
  81  */
  82 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
  83                                       struct page *page_for_lower,
  84                                       size_t offset_in_page, size_t size)
  85 {
  86         char *virt;
  87         loff_t offset;
  88         int rc;
  89
  90         offset = ((((off_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
  91                   + offset_in_page);
  92         virt = kmap(page_for_lower);
  93         rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
  94         kunmap(page_for_lower);
  95         return rc;
  96 }
  97
  98 /**
  99  * ecryptfs_write
 100  * @ecryptfs_file: The eCryptfs file into which to write
 101  * @data: Virtual address where data to write is located
 102  * @offset: Offset in the eCryptfs file at which to begin writing the
 103  *          data from @data
 104  * @size: The number of bytes to write from @data
 105  *
 106  * Write an arbitrary amount of data to an arbitrary location in the
 107  * eCryptfs inode page cache. This is done on a page-by-page, and then
 108  * by an extent-by-extent, basis; individual extents are encrypted and
 109  * written to the lower page cache (via VFS writes). This function
 110  * takes care of all the address translation to locations in the lower
 111  * filesystem; it also handles truncate events, writing out zeros
 112  * where necessary.
 113  *
 114  * Returns zero on success; non-zero otherwise
 115  */
 116 int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset,
 117                    size_t size)
 118 {
 119         struct page *ecryptfs_page;
 120         char *ecryptfs_page_virt;
 121         loff_t ecryptfs_file_size =
 122                 i_size_read(ecryptfs_file->f_dentry->d_inode);
 123         loff_t data_offset = 0;
 124         loff_t pos;
 125         int rc = 0;
 126
 127         if (offset > ecryptfs_file_size)
 128                 pos = ecryptfs_file_size;
 129         else
 130                 pos = offset;
 131         while (pos < (offset + size)) {
 132                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 133                 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 134                 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 135                 size_t total_remaining_bytes = ((offset + size) - pos);
 136
 137                 if (num_bytes > total_remaining_bytes)
 138                         num_bytes = total_remaining_bytes;
 139                 if (pos < offset) {
 140                         size_t total_remaining_zeros = (offset - pos);
 141
 142                         if (num_bytes > total_remaining_zeros)
 143                                 num_bytes = total_remaining_zeros;
 144                 }
 145                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
 146                                                          ecryptfs_page_idx);
 147                 if (IS_ERR(ecryptfs_page)) {
 148                         rc = PTR_ERR(ecryptfs_page);
 149                         printk(KERN_ERR "%s: Error getting page at "
 150                                "index [%ld] from eCryptfs inode "
 151                                "mapping; rc = [%d]\n", __FUNCTION__,
 152                                ecryptfs_page_idx, rc);
 153                         goto out;
 154                 }
 155                 if (start_offset_in_page) {
 156                         /* Read in the page from the lower
 157                          * into the eCryptfs inode page cache,
 158                          * decrypting */
 159                         rc = ecryptfs_decrypt_page(ecryptfs_page);
 160                         if (rc) {
 161                                 printk(KERN_ERR "%s: Error decrypting "
 162                                        "page; rc = [%d]\n",
 163                                        __FUNCTION__, rc);
 164                                 ClearPageUptodate(ecryptfs_page);
 165                                 page_cache_release(ecryptfs_page);
 166                                 goto out;
 167                         }
 168                 }
 169                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
 170                 if (pos >= offset) {
 171                         memcpy(((char *)ecryptfs_page_virt
 172                                 + start_offset_in_page),
 173                                (data + data_offset), num_bytes);
 174                         data_offset += num_bytes;
 175                 } else {
 176                         /* We are extending past the previous end of the file.
 177                          * Fill in zero values up to the start of where we
 178                          * will be writing data. */
 179                         memset(((char *)ecryptfs_page_virt
 180                                 + start_offset_in_page), 0, num_bytes);
 181                 }
 182                 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
 183                 flush_dcache_page(ecryptfs_page);
 184                 SetPageUptodate(ecryptfs_page);
 185                 unlock_page(ecryptfs_page);
 186                 rc = ecryptfs_encrypt_page(ecryptfs_page);
 187                 page_cache_release(ecryptfs_page);
 188                 if (rc) {
 189                         printk(KERN_ERR "%s: Error encrypting "
 190                                "page; rc = [%d]\n", __FUNCTION__, rc);
 191                         goto out;
 192                 }
 193                 pos += num_bytes;
 194         }
 195         if ((offset + size) > ecryptfs_file_size) {
 196                 i_size_write(ecryptfs_file->f_dentry->d_inode, (offset + size));
 197                 rc = ecryptfs_write_inode_size_to_metadata(
 198                         ecryptfs_file->f_dentry->d_inode);
 199                 if (rc) {
 200                         printk(KERN_ERR "Problem with "
 201                                "ecryptfs_write_inode_size_to_metadata; "
 202                                "rc = [%d]\n", rc);
 203                         goto out;
 204                 }
 205         }
 206 out:
 207         return rc;
 208 }
 209
 210 /**
 211  * ecryptfs_read_lower
 212  * @data: The read data is stored here by this function
 213  * @offset: Byte offset in the lower file from which to read the data
 214  * @size: Number of bytes to read from @offset of the lower file and
 215  *        store into @data
 216  * @ecryptfs_inode: The eCryptfs inode
 217  *
 218  * Read @size bytes of data at byte offset @offset from the lower
 219  * inode into memory location @data.
 220  *
 221  * Returns zero on success; non-zero on error
 222  */
 223 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 224                         struct inode *ecryptfs_inode)
 225 {
 226         struct ecryptfs_inode_info *inode_info =
 227                 ecryptfs_inode_to_private(ecryptfs_inode);
 228         ssize_t octets_read;
 229         mm_segment_t fs_save;
 230         int rc = 0;
 231
 232         mutex_lock(&inode_info->lower_file_mutex);
 233         BUG_ON(!inode_info->lower_file);
 234         inode_info->lower_file->f_pos = offset;
 235         fs_save = get_fs();
 236         set_fs(get_ds());
 237         octets_read = vfs_read(inode_info->lower_file, data, size,
 238                                &inode_info->lower_file->f_pos);
 239         set_fs(fs_save);
 240         if (octets_read < 0) {
 241                 printk(KERN_ERR "%s: octets_read = [%td]; "
 242                        "expected [%td]\n", __FUNCTION__, octets_read, size);
 243                 rc = -EINVAL;
 244         }
 245         mutex_unlock(&inode_info->lower_file_mutex);
 246         return rc;
 247 }
 248
 249 /**
 250  * ecryptfs_read_lower_page_segment
 251  * @page_for_ecryptfs: The page into which data for eCryptfs will be
 252  *                     written
 253  * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 254  *                  writing
 255  * @size: The number of bytes to write into @page_for_ecryptfs
 256  * @ecryptfs_inode: The eCryptfs inode
 257  *
 258  * Determines the byte offset in the file for the given page and
 259  * offset within the page, maps the page, and makes the call to read
 260  * the contents of @page_for_ecryptfs from the lower inode.
 261  *
 262  * Returns zero on success; non-zero otherwise
 263  */
 264 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
 265                                      pgoff_t page_index,
 266                                      size_t offset_in_page, size_t size,
 267                                      struct inode *ecryptfs_inode)
 268 {
 269         char *virt;
 270         loff_t offset;
 271         int rc;
 272
 273         offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
 274         virt = kmap(page_for_ecryptfs);
 275         rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 276         kunmap(page_for_ecryptfs);
 277         flush_dcache_page(page_for_ecryptfs);
 278         return rc;
 279 }
 280
 281 /**
 282  * ecryptfs_read
 283  * @data: The virtual address into which to write the data read (and
 284  *        possibly decrypted) from the lower file
 285  * @offset: The offset in the decrypted view of the file from which to
 286  *          read into @data
 287  * @size: The number of bytes to read into @data
 288  * @ecryptfs_file: The eCryptfs file from which to read
 289  *
 290  * Read an arbitrary amount of data from an arbitrary location in the
 291  * eCryptfs page cache. This is done on an extent-by-extent basis;
 292  * individual extents are decrypted and read from the lower page
 293  * cache (via VFS reads). This function takes care of all the
 294  * address translation to locations in the lower filesystem.
 295  *
 296  * Returns zero on success; non-zero otherwise
 297  */
 298 int ecryptfs_read(char *data, loff_t offset, size_t size,
 299                   struct file *ecryptfs_file)
 300 {
 301         struct page *ecryptfs_page;
 302         char *ecryptfs_page_virt;
 303         loff_t ecryptfs_file_size =
 304                 i_size_read(ecryptfs_file->f_dentry->d_inode);
 305         loff_t data_offset = 0;
 306         loff_t pos;
 307         int rc = 0;
 308
 309         if ((offset + size) > ecryptfs_file_size) {
 310                 rc = -EINVAL;
 311                 printk(KERN_ERR "%s: Attempt to read data past the end of the "
 312                         "file; offset = [%lld]; size = [%td]; "
 313                        "ecryptfs_file_size = [%lld]\n",
 314                        __FUNCTION__, offset, size, ecryptfs_file_size);
 315                 goto out;
 316         }
 317         pos = offset;
 318         while (pos < (offset + size)) {
 319                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 320                 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 321                 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 322                 size_t total_remaining_bytes = ((offset + size) - pos);
 323
 324                 if (num_bytes > total_remaining_bytes)
 325                         num_bytes = total_remaining_bytes;
 326                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
 327                                                          ecryptfs_page_idx);
 328                 if (IS_ERR(ecryptfs_page)) {
 329                         rc = PTR_ERR(ecryptfs_page);
 330                         printk(KERN_ERR "%s: Error getting page at "
 331                                "index [%ld] from eCryptfs inode "
 332                                "mapping; rc = [%d]\n", __FUNCTION__,
 333                                ecryptfs_page_idx, rc);
 334                         goto out;
 335                 }
 336                 rc = ecryptfs_decrypt_page(ecryptfs_page);
 337                 if (rc) {
 338                         printk(KERN_ERR "%s: Error decrypting "
 339                                "page; rc = [%d]\n", __FUNCTION__, rc);
 340                         ClearPageUptodate(ecryptfs_page);
 341                         page_cache_release(ecryptfs_page);
 342                         goto out;
 343                 }
 344                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
 345                 memcpy((data + data_offset),
 346                        ((char *)ecryptfs_page_virt + start_offset_in_page),
 347                        num_bytes);
 348                 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
 349                 flush_dcache_page(ecryptfs_page);
 350                 SetPageUptodate(ecryptfs_page);
 351                 unlock_page(ecryptfs_page);
 352                 page_cache_release(ecryptfs_page);
 353                 pos += num_bytes;
 354                 data_offset += num_bytes;
 355         }
 356 out:
 357         return rc;
 358 }