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