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