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 bytes written on success; less than 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         mm_segment_t fs_save;
  44         ssize_t rc;
  45
  46         inode_info = ecryptfs_inode_to_private(ecryptfs_inode);
  47         mutex_lock(&inode_info->lower_file_mutex);
  48         BUG_ON(!inode_info->lower_file);
  49         inode_info->lower_file->f_pos = offset;
  50         fs_save = get_fs();
  51         set_fs(get_ds());
  52         rc = vfs_write(inode_info->lower_file, data, size,
  53                        &inode_info->lower_file->f_pos);
  54         set_fs(fs_save);
  55         mutex_unlock(&inode_info->lower_file_mutex);
  56         mark_inode_dirty_sync(ecryptfs_inode);
  57         return rc;
  58 }
  59
  60 /**
  61  * ecryptfs_write_lower_page_segment
  62  * @ecryptfs_inode: The eCryptfs inode
  63  * @page_for_lower: The page containing the data to be written to the
  64  *                  lower file
  65  * @offset_in_page: The offset in the @page_for_lower from which to
  66  *                  start writing the data
  67  * @size: The amount of data from @page_for_lower to write to the
  68  *        lower file
  69  *
  70  * Determines the byte offset in the file for the given page and
  71  * offset within the page, maps the page, and makes the call to write
  72  * the contents of @page_for_lower to the lower inode.
  73  *
  74  * Returns zero on success; non-zero otherwise
  75  */
  76 int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode,
  77                                       struct page *page_for_lower,
  78                                       size_t offset_in_page, size_t size)
  79 {
  80         char *virt;
  81         loff_t offset;
  82         int rc;
  83
  84         offset = ((((loff_t)page_for_lower->index) << PAGE_CACHE_SHIFT)
  85                   + offset_in_page);
  86         virt = kmap(page_for_lower);
  87         rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size);
  88         if (rc > 0)
  89                 rc = 0;
  90         kunmap(page_for_lower);
  91         return rc;
  92 }
  93
  94 /**
  95  * ecryptfs_write
  96  * @ecryptfs_file: The eCryptfs file into which to write
  97  * @data: Virtual address where data to write is located
  98  * @offset: Offset in the eCryptfs file at which to begin writing the
  99  *          data from @data
 100  * @size: The number of bytes to write from @data
 101  *
 102  * Write an arbitrary amount of data to an arbitrary location in the
 103  * eCryptfs inode page cache. This is done on a page-by-page, and then
 104  * by an extent-by-extent, basis; individual extents are encrypted and
 105  * written to the lower page cache (via VFS writes). This function
 106  * takes care of all the address translation to locations in the lower
 107  * filesystem; it also handles truncate events, writing out zeros
 108  * where necessary.
 109  *
 110  * Returns zero on success; non-zero otherwise
 111  */
 112 int ecryptfs_write(struct file *ecryptfs_file, char *data, loff_t offset,
 113                    size_t size)
 114 {
 115         struct page *ecryptfs_page;
 116         struct ecryptfs_crypt_stat *crypt_stat;
 117         struct inode *ecryptfs_inode = ecryptfs_file->f_dentry->d_inode;
 118         char *ecryptfs_page_virt;
 119         loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode);
 120         loff_t data_offset = 0;
 121         loff_t pos;
 122         int rc = 0;
 123
 124         crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
 125         /*
 126          * if we are writing beyond current size, then start pos
 127          * at the current size - we'll fill in zeros from there.
 128          */
 129         if (offset > ecryptfs_file_size)
 130                 pos = ecryptfs_file_size;
 131         else
 132                 pos = offset;
 133         while (pos < (offset + size)) {
 134                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 135                 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 136                 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 137                 size_t total_remaining_bytes = ((offset + size) - pos);
 138
 139                 if (num_bytes > total_remaining_bytes)
 140                         num_bytes = total_remaining_bytes;
 141                 if (pos < offset) {
 142                         /* remaining zeros to write, up to destination offset */
 143                         size_t total_remaining_zeros = (offset - pos);
 144
 145                         if (num_bytes > total_remaining_zeros)
 146                                 num_bytes = total_remaining_zeros;
 147                 }
 148                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
 149                                                          ecryptfs_page_idx);
 150                 if (IS_ERR(ecryptfs_page)) {
 151                         rc = PTR_ERR(ecryptfs_page);
 152                         printk(KERN_ERR "%s: Error getting page at "
 153                                "index [%ld] from eCryptfs inode "
 154                                "mapping; rc = [%d]\n", __func__,
 155                                ecryptfs_page_idx, rc);
 156                         goto out;
 157                 }
 158                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
 159
 160                 /*
 161                  * pos: where we're now writing, offset: where the request was
 162                  * If current pos is before request, we are filling zeros
 163                  * If we are at or beyond request, we are writing the *data*
 164                  * If we're in a fresh page beyond eof, zero it in either case
 165                  */
 166                 if (pos < offset || !start_offset_in_page) {
 167                         /* We are extending past the previous end of the file.
 168                          * Fill in zero values to the end of the page */
 169                         memset(((char *)ecryptfs_page_virt
 170                                 + start_offset_in_page), 0,
 171                                 PAGE_CACHE_SIZE - start_offset_in_page);
 172                 }
 173
 174                 /* pos >= offset, we are now writing the data request */
 175                 if (pos >= offset) {
 176                         memcpy(((char *)ecryptfs_page_virt
 177                                 + start_offset_in_page),
 178                                (data + data_offset), num_bytes);
 179                         data_offset += num_bytes;
 180                 }
 181                 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
 182                 flush_dcache_page(ecryptfs_page);
 183                 SetPageUptodate(ecryptfs_page);
 184                 unlock_page(ecryptfs_page);
 185                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED)
 186                         rc = ecryptfs_encrypt_page(ecryptfs_page);
 187                 else
 188                         rc = ecryptfs_write_lower_page_segment(ecryptfs_inode,
 189                                                 ecryptfs_page,
 190                                                 start_offset_in_page,
 191                                                 data_offset);
 192                 page_cache_release(ecryptfs_page);
 193                 if (rc) {
 194                         printk(KERN_ERR "%s: Error encrypting "
 195                                "page; rc = [%d]\n", __func__, rc);
 196                         goto out;
 197                 }
 198                 pos += num_bytes;
 199         }
 200         if ((offset + size) > ecryptfs_file_size) {
 201                 i_size_write(ecryptfs_inode, (offset + size));
 202                 if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
 203                         rc = ecryptfs_write_inode_size_to_metadata(
 204                                                                 ecryptfs_inode);
 205                         if (rc) {
 206                                 printk(KERN_ERR "Problem with "
 207                                        "ecryptfs_write_inode_size_to_metadata; "
 208                                        "rc = [%d]\n", rc);
 209                                 goto out;
 210                         }
 211                 }
 212         }
 213 out:
 214         return rc;
 215 }
 216
 217 /**
 218  * ecryptfs_read_lower
 219  * @data: The read data is stored here by this function
 220  * @offset: Byte offset in the lower file from which to read the data
 221  * @size: Number of bytes to read from @offset of the lower file and
 222  *        store into @data
 223  * @ecryptfs_inode: The eCryptfs inode
 224  *
 225  * Read @size bytes of data at byte offset @offset from the lower
 226  * inode into memory location @data.
 227  *
 228  * Returns bytes read on success; 0 on EOF; less than zero on error
 229  */
 230 int ecryptfs_read_lower(char *data, loff_t offset, size_t size,
 231                         struct inode *ecryptfs_inode)
 232 {
 233         struct ecryptfs_inode_info *inode_info =
 234                 ecryptfs_inode_to_private(ecryptfs_inode);
 235         mm_segment_t fs_save;
 236         ssize_t rc;
 237
 238         mutex_lock(&inode_info->lower_file_mutex);
 239         BUG_ON(!inode_info->lower_file);
 240         inode_info->lower_file->f_pos = offset;
 241         fs_save = get_fs();
 242         set_fs(get_ds());
 243         rc = vfs_read(inode_info->lower_file, data, size,
 244                       &inode_info->lower_file->f_pos);
 245         set_fs(fs_save);
 246         mutex_unlock(&inode_info->lower_file_mutex);
 247         return rc;
 248 }
 249
 250 /**
 251  * ecryptfs_read_lower_page_segment
 252  * @page_for_ecryptfs: The page into which data for eCryptfs will be
 253  *                     written
 254  * @offset_in_page: Offset in @page_for_ecryptfs from which to start
 255  *                  writing
 256  * @size: The number of bytes to write into @page_for_ecryptfs
 257  * @ecryptfs_inode: The eCryptfs inode
 258  *
 259  * Determines the byte offset in the file for the given page and
 260  * offset within the page, maps the page, and makes the call to read
 261  * the contents of @page_for_ecryptfs from the lower inode.
 262  *
 263  * Returns zero on success; non-zero otherwise
 264  */
 265 int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs,
 266                                      pgoff_t page_index,
 267                                      size_t offset_in_page, size_t size,
 268                                      struct inode *ecryptfs_inode)
 269 {
 270         char *virt;
 271         loff_t offset;
 272         int rc;
 273
 274         offset = ((((loff_t)page_index) << PAGE_CACHE_SHIFT) + offset_in_page);
 275         virt = kmap(page_for_ecryptfs);
 276         rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode);
 277         if (rc > 0)
 278                 rc = 0;
 279         kunmap(page_for_ecryptfs);
 280         flush_dcache_page(page_for_ecryptfs);
 281         return rc;
 282 }
 283
 284 #if 0
 285 /**
 286  * ecryptfs_read
 287  * @data: The virtual address into which to write the data read (and
 288  *        possibly decrypted) from the lower file
 289  * @offset: The offset in the decrypted view of the file from which to
 290  *          read into @data
 291  * @size: The number of bytes to read into @data
 292  * @ecryptfs_file: The eCryptfs file from which to read
 293  *
 294  * Read an arbitrary amount of data from an arbitrary location in the
 295  * eCryptfs page cache. This is done on an extent-by-extent basis;
 296  * individual extents are decrypted and read from the lower page
 297  * cache (via VFS reads). This function takes care of all the
 298  * address translation to locations in the lower filesystem.
 299  *
 300  * Returns zero on success; non-zero otherwise
 301  */
 302 int ecryptfs_read(char *data, loff_t offset, size_t size,
 303                   struct file *ecryptfs_file)
 304 {
 305         struct page *ecryptfs_page;
 306         char *ecryptfs_page_virt;
 307         loff_t ecryptfs_file_size =
 308                 i_size_read(ecryptfs_file->f_dentry->d_inode);
 309         loff_t data_offset = 0;
 310         loff_t pos;
 311         int rc = 0;
 312
 313         if ((offset + size) > ecryptfs_file_size) {
 314                 rc = -EINVAL;
 315                 printk(KERN_ERR "%s: Attempt to read data past the end of the "
 316                         "file; offset = [%lld]; size = [%td]; "
 317                        "ecryptfs_file_size = [%lld]\n",
 318                        __func__, offset, size, ecryptfs_file_size);
 319                 goto out;
 320         }
 321         pos = offset;
 322         while (pos < (offset + size)) {
 323                 pgoff_t ecryptfs_page_idx = (pos >> PAGE_CACHE_SHIFT);
 324                 size_t start_offset_in_page = (pos & ~PAGE_CACHE_MASK);
 325                 size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 326                 size_t total_remaining_bytes = ((offset + size) - pos);
 327
 328                 if (num_bytes > total_remaining_bytes)
 329                         num_bytes = total_remaining_bytes;
 330                 ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_file,
 331                                                          ecryptfs_page_idx);
 332                 if (IS_ERR(ecryptfs_page)) {
 333                         rc = PTR_ERR(ecryptfs_page);
 334                         printk(KERN_ERR "%s: Error getting page at "
 335                                "index [%ld] from eCryptfs inode "
 336                                "mapping; rc = [%d]\n", __func__,
 337                                ecryptfs_page_idx, rc);
 338                         goto out;
 339                 }
 340                 ecryptfs_page_virt = kmap_atomic(ecryptfs_page, KM_USER0);
 341                 memcpy((data + data_offset),
 342                        ((char *)ecryptfs_page_virt + start_offset_in_page),
 343                        num_bytes);
 344                 kunmap_atomic(ecryptfs_page_virt, KM_USER0);
 345                 flush_dcache_page(ecryptfs_page);
 346                 SetPageUptodate(ecryptfs_page);
 347                 unlock_page(ecryptfs_page);
 348                 page_cache_release(ecryptfs_page);
 349                 pos += num_bytes;
 350                 data_offset += num_bytes;
 351         }
 352 out:
 353         return rc;
 354 }
 355 #endif  /*  0  */