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 = ((((loff_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         /*
 128          * if we are writing beyond current size, then start pos
 129          * at the current size - we'll fill in zeros from there.
 130          */
 131         if (offset > ecryptfs_file_size)
 132                 pos = ecryptfs_file_size;
 133         else
 134                 pos = offset;
 135         while (pos < (offset + size)) {
 136                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 137                 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 138                 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 139                 size_t total_remaining_bytes = ((offset + size) - pos);
 140
 141                 if (num_bytes > total_remaining_bytes)
 142                         num_bytes = total_remaining_bytes;
 143                 if (pos < offset) {
 144                         /* remaining zeros to write, up to destination offset */
 145                         size_t total_remaining_zeros = (offset - pos);
 146
 147                         if (num_bytes > total_remaining_zeros)
 148                                 num_bytes = total_remaining_zeros;
 149                 }
 150                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
 151                                                          ecryptfs_page_idx);
 152                 if (IS_ERR(ecryptfs_page)) {
 153                         rc = PTR_ERR(ecryptfs_page);
 154                         printk(KERN_ERR "%s: Error getting page at "
 155                                "index [%ld] from eCryptfs inode "
 156                                "mapping; rc = [%d]\n", __FUNCTION__,
 157                                ecryptfs_page_idx, rc);
 158                         goto out;
 159                 }
 160                 if (start_offset_in_page) {
 161                         /* Read in the page from the lower
 162                          * into the eCryptfs inode page cache,
 163                          * decrypting */
 164                         rc = ecryptfs_decrypt_page(ecryptfs_page);
 165                         if (rc) {
 166                                 printk(KERN_ERR "%s: Error decrypting "
 167                                        "page; rc = [%d]\n",
 168                                        __FUNCTION__, rc);
 169                                 ClearPageUptodate(ecryptfs_page);
 170                                 page_cache_release(ecryptfs_page);
 171                                 goto out;
 172                         }
 173                 }
 174                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
 175
 176                 /*
 177                  * pos: where we're now writing, offset: where the request was
 178                  * If current pos is before request, we are filling zeros
 179                  * If we are at or beyond request, we are writing the *data*
 180                  * If we're in a fresh page beyond eof, zero it in either case
 181                  */
 182                 if (pos < offset || !start_offset_in_page) {
 183                         /* We are extending past the previous end of the file.
 184                          * Fill in zero values to the end of the page */
 185                         memset(((char *)ecryptfs_page_virt
 186                                 + start_offset_in_page), 0,
 187                                 PAGE_CACHE_SIZE - start_offset_in_page);
 188                 }
 189
 190                 /* pos >= offset, we are now writing the data request */
 191                 if (pos >= offset) {
 192                         memcpy(((char *)ecryptfs_page_virt
 193                                 + start_offset_in_page),
 194                                (data + data_offset), num_bytes);
 195                         data_offset += num_bytes;
 196                 }
 197                 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
 198                 flush_dcache_page(ecryptfs_page);
 199                 SetPageUptodate(ecryptfs_page);
 200                 unlock_page(ecryptfs_page);
 201                 rc = ecryptfs_encrypt_page(ecryptfs_page);
 202                 page_cache_release(ecryptfs_page);
 203                 if (rc) {
 204                         printk(KERN_ERR "%s: Error encrypting "
 205                                "page; rc = [%d]\n", __FUNCTION__, rc);
 206                         goto out;
 207                 }
 208                 pos += num_bytes;
 209         }
 210         if ((offset + size) > ecryptfs_file_size) {
 211                 i_size_write(ecryptfs_file->f_dentry->d_inode, (offset + size));
 212                 rc = ecryptfs_write_inode_size_to_metadata(
 213                         ecryptfs_file->f_dentry->d_inode);
 214                 if (rc) {
 215                         printk(KERN_ERR "Problem with "
 216                                "ecryptfs_write_inode_size_to_metadata; "
 217                                "rc = [%d]\n", rc);
 218                         goto out;
 219                 }
 220         }
 221 out:
 222         return rc;
 223 }
 224
 225 /**
 226  * ecryptfs_read_lower
 227  * @data: The read data is stored here by this function
 228  * @offset: Byte offset in the lower file from which to read the data
 229  * @size: Number of bytes to read from @offset of the lower file and
 230  *        store into @data
 231  * @ecryptfs_inode: The eCryptfs inode
 232  *
 233  * Read @size bytes of data at byte offset @offset from the lower
 234  * inode into memory location @data.
 235  *
 236  * Returns zero on success; non-zero on error
 237  */
 238 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 239                         struct inode *ecryptfs_inode)
 240 {
 241         struct ecryptfs_inode_info *inode_info =
 242                 ecryptfs_inode_to_private(ecryptfs_inode);
 243         ssize_t octets_read;
 244         mm_segment_t fs_save;
 245         int rc = 0;
 246
 247         mutex_lock(&inode_info->lower_file_mutex);
 248         BUG_ON(!inode_info->lower_file);
 249         inode_info->lower_file->f_pos = offset;
 250         fs_save = get_fs();
 251         set_fs(get_ds());
 252         octets_read = vfs_read(inode_info->lower_file, data, size,
 253                                &inode_info->lower_file->f_pos);
 254         set_fs(fs_save);
 255         if (octets_read < 0) {
 256                 printk(KERN_ERR "%s: octets_read = [%td]; "
 257                        "expected [%td]\n", __FUNCTION__, octets_read, size);
 258                 rc = -EINVAL;
 259         }
 260         mutex_unlock(&inode_info->lower_file_mutex);
 261         return rc;
 262 }
 263
 264 /**
 265  * ecryptfs_read_lower_page_segment
 266  * @page_for_ecryptfs: The page into which data for eCryptfs will be
 267  *                     written
 268  * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 269  *                  writing
 270  * @size: The number of bytes to write into @page_for_ecryptfs
 271  * @ecryptfs_inode: The eCryptfs inode
 272  *
 273  * Determines the byte offset in the file for the given page and
 274  * offset within the page, maps the page, and makes the call to read
 275  * the contents of @page_for_ecryptfs from the lower inode.
 276  *
 277  * Returns zero on success; non-zero otherwise
 278  */
 279 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
 280                                      pgoff_t page_index,
 281                                      size_t offset_in_page, size_t size,
 282                                      struct inode *ecryptfs_inode)
 283 {
 284         char *virt;
 285         loff_t offset;
 286         int rc;
 287
 288         offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
 289         virt = kmap(page_for_ecryptfs);
 290         rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 291         kunmap(page_for_ecryptfs);
 292         flush_dcache_page(page_for_ecryptfs);
 293         return rc;
 294 }
 295
 296 /**
 297  * ecryptfs_read
 298  * @data: The virtual address into which to write the data read (and
 299  *        possibly decrypted) from the lower file
 300  * @offset: The offset in the decrypted view of the file from which to
 301  *          read into @data
 302  * @size: The number of bytes to read into @data
 303  * @ecryptfs_file: The eCryptfs file from which to read
 304  *
 305  * Read an arbitrary amount of data from an arbitrary location in the
 306  * eCryptfs page cache. This is done on an extent-by-extent basis;
 307  * individual extents are decrypted and read from the lower page
 308  * cache (via VFS reads). This function takes care of all the
 309  * address translation to locations in the lower filesystem.
 310  *
 311  * Returns zero on success; non-zero otherwise
 312  */
 313 int ecryptfs_read(char *data, loff_t offset, size_t size,
 314                   struct file *ecryptfs_file)
 315 {
 316         struct page *ecryptfs_page;
 317         char *ecryptfs_page_virt;
 318         loff_t ecryptfs_file_size =
 319                 i_size_read(ecryptfs_file->f_dentry->d_inode);
 320         loff_t data_offset = 0;
 321         loff_t pos;
 322         int rc = 0;
 323
 324         if ((offset + size) > ecryptfs_file_size) {
 325                 rc = -EINVAL;
 326                 printk(KERN_ERR "%s: Attempt to read data past the end of the "
 327                         "file; offset = [%lld]; size = [%td]; "
 328                        "ecryptfs_file_size = [%lld]\n",
 329                        __FUNCTION__, offset, size, ecryptfs_file_size);
 330                 goto out;
 331         }
 332         pos = offset;
 333         while (pos < (offset + size)) {
 334                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 335                 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 336                 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 337                 size_t total_remaining_bytes = ((offset + size) - pos);
 338
 339                 if (num_bytes > total_remaining_bytes)
 340                         num_bytes = total_remaining_bytes;
 341                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
 342                                                          ecryptfs_page_idx);
 343                 if (IS_ERR(ecryptfs_page)) {
 344                         rc = PTR_ERR(ecryptfs_page);
 345                         printk(KERN_ERR "%s: Error getting page at "
 346                                "index [%ld] from eCryptfs inode "
 347                                "mapping; rc = [%d]\n", __FUNCTION__,
 348                                ecryptfs_page_idx, rc);
 349                         goto out;
 350                 }
 351                 rc = ecryptfs_decrypt_page(ecryptfs_page);
 352                 if (rc) {
 353                         printk(KERN_ERR "%s: Error decrypting "
 354                                "page; rc = [%d]\n", __FUNCTION__, rc);
 355                         ClearPageUptodate(ecryptfs_page);
 356                         page_cache_release(ecryptfs_page);
 357                         goto out;
 358                 }
 359                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
 360                 memcpy((data + data_offset),
 361                        ((char *)ecryptfs_page_virt + start_offset_in_page),
 362                        num_bytes);
 363                 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
 364                 flush_dcache_page(ecryptfs_page);
 365                 SetPageUptodate(ecryptfs_page);
 366                 unlock_page(ecryptfs_page);
 367                 page_cache_release(ecryptfs_page);
 368                 pos += num_bytes;
 369                 data_offset += num_bytes;
 370         }
 371 out:
 372         return rc;
 373 }